Water Supply

Water Supply and Distribution

Reference text for the water supply area. Every rule below is written from the printed line of the

2024 International Plumbing Code (IPC 2024) that carries it, and each rule names the section it comes

from. Where the printed line does not state a value, no value is stated here.

1. Scope and required water

Chapter 6 governs the materials, design and installation of water supply systems, both hot and cold,

for utilization in connection with human occupancy and habitation, and governs the installation of

individual water supply systems (IPC 2024, 601.1).

Structures equipped with plumbing fixtures and used for human occupancy or habitation must be

provided with a potable supply of water in the amounts and at the pressures specified in the chapter

(IPC 2024, 602.1). Only potable water may be supplied to plumbing fixtures that provide water for

drinking, bathing or culinary purposes, or for the processing of food, medical or pharmaceutical

products; unless the code provides otherwise, potable water must be supplied to all plumbing fixtures

(IPC 2024, 602.2).

Solar energy systems used for heating potable water, or using an independent medium for heating

potable water, must comply with the applicable requirements of the code, and their use must not

compromise the cross-connection or potable-supply protection requirements (IPC 2024, 601.2).

Existing metallic water service piping used for electrical grounding must not be replaced with

nonmetallic pipe or tubing until other approved means of grounding is provided (IPC 2024, 601.3).

The potable water distribution system is tested in accordance with Section 312.6 (IPC 2024, 601.4),

and pressure piping systems rehabilitated with an epoxy lining system must use a lining system

complying with ASTM F2831 (IPC 2024, 601.5).

2. Individual water supply

Where a potable public water supply is not available, individual sources of potable water supply must

be used (IPC 2024, 602.3). The recognized types of individual supply — depending on geological and

soil conditions and the amount of rainfall — are the drilled well, driven well, dug well, bored well,

spring, stream or cistern. Surface bodies of water and land cisterns are not acceptable sources unless

properly treated by approved means to prevent contamination; individual supplies must be constructed

and installed in accordance with applicable state and local laws, and, where those laws do not address

all the requirements of NGWA-01, must comply with NGWA-01 for the requirements those laws do not

address (IPC 2024, 602.3.1).

The combined capacity of source and storage must supply the fixtures with water at the rates and

pressures the chapter requires (IPC 2024, 602.3.2). Water from an individual supply must be approved as

potable by the authority having jurisdiction before connection to the plumbing system (IPC 2024,

602.3.3), and after construction the system must be purged of deleterious matter and disinfected in

accordance with Section 610 (IPC 2024, 602.3.4).

Pumps must be rated for the transport of potable water, be built and installed to prevent

contamination entering the potable supply through the pump units, conform to NSF 61 where they supply

drinking water, be sealed to the well casing or covered with a watertight seal, be designed to

maintain a prime, and be installed with ready access to the pump parts of the entire assembly for

repairs (IPC 2024, 602.3.5). The pump room or enclosure around a well pump must be drained and

protected from freezing by heating or other approved means; pumps installed in basements must be

mounted on a block or shelf not less than 18 inches (457 mm) above the basement floor, and well pits

are prohibited (IPC 2024, 602.3.5.1).

3. Water service

The water service pipe must be sized to supply the structure in the quantities and at the pressures

the code requires, and must be not less than 3/4 inch (19.1 mm) in diameter (IPC 2024, 603.1).

Separation from the building sewer, where the water service is in the same trench: if the building

sewer is not constructed of a material listed in Table 702.2, water service pipe and building sewer

must be horizontally separated by not less than 5 feet (1524 mm) of undisturbed or compacted earth.

That separation does not apply where the water service crosses a sewer pipe, provided the water

service is sleeved to a point not less than 5 feet (1524 mm) horizontally from the sewer pipe

centerline on both sides of the crossing; the sleeve must be of pipe materials listed in Table 605.3,

702.2 or 702.3. It also does not apply where the bottom of the water service pipe, within 5 feet

(1524 mm) of the sewer, is not less than 12 inches (305 mm) above the highest point of the top of the

building sewer (IPC 2024, 603.2). Potable water service pipes must not be located in, under or above

cesspools, septic tanks, septic tank drainage fields or seepage pits; where soil or ground water

creates contaminated conditions for piping, analysis is required in accordance with Section 605.1

(IPC 2024, 603.2.1).

Pipe selection. Water service pipe must conform to NSF 61 and to one of the standards listed in

Table 605.3. Water service pipe or tubing installed underground and outside the structure must have a

working pressure rating of not less than 160 psi (1100 kPa) at 73.4°F (23°C); where the water pressure

exceeds 160 psi (1100 kPa), the piping material must have a working pressure rating not less than the

highest available pressure. Water service piping materials that are not third-party certified for

water distribution must terminate at or before the full-open valve located at the entrance to the

structure, and ductile iron water service piping must be cement mortar lined in accordance with

AWWA C104/A21.4 (IPC 2024, 605.3). Dual check-valve-type backflow preventers installed on the water

supply system must comply with ASSE 1024 or CSA B64.6 (IPC 2024, 605.3.1).

Water distribution pipe and tubing must conform to NSF 61 and to one of the standards listed in

Table 605.4, and hot water distribution pipe and tubing must have a pressure rating of not less than

100 psi (690 kPa) at 180°F (82°C) (IPC 2024, 605.4).

Water distribution is served by a shorter list: CPVC, CPVC/AL/CPVC, copper or copper-alloy pipe and

tubing, PEX, PEX-AL-PEX, PEX-AL-HDPE, ductile iron, galvanized steel, PE-AL-PE composite, PE-RT,

polypropylene, and stainless steel pipe and tubing of Type 304/304L and 316/316L (IPC 2024,

Table 605.4).

4. Design of the building water distribution system

The design must conform to accepted engineering practice, and the methods used to determine pipe sizes

must be approved (IPC 2024, 604.1). At the points of interconnection between the hot and cold water

supply piping systems and the individual fixtures, appliances or devices, provisions must be made to

prevent flow between those piping systems (IPC 2024, 604.2).

4.1 Required capacity at fixture supply outlets (Table 604.3)

Under conditions of peak demand, the capacities at the fixture supply pipe outlets must be not less

than the values of Table 604.3; for fixtures and appliances not listed there, the minimum flow rate

and flow pressure follow the manufacturer's installation instructions (IPC 2024, 604.3).

For SI: 1 pound per square inch = 6.895 kPa, 1 gallon per minute = 3.785 L/m. Where the shower mixing

valve manufacturer indicates a lower flow rating for the mixing valve, the lower value applies

(IPC 2024, Table 604.3, footnote b).

4.2 Maximum flow and water consumption (Table 604.4)

Maximum water consumption flow rates and quantities for all plumbing fixtures and fixture fittings

follow Table 604.4 (IPC 2024, 604.4).

A hand-held shower spray is a shower head, and shower heads must comply with all requirements for

high-efficiency showerheads in ASME A112.18.1-2020/CSA B125.1 (IPC 2024, Table 604.4, footnotes a

and c). The exceptions to Section 604.4 are blowout design water closets having a water consumption

not greater than 3 1/2 gallons (13 L) per flushing cycle, vegetable sprays, clinical sinks having a

water consumption not greater than 4 1/2 gallons (17 L) per flushing cycle, service sinks and

emergency showers.

4.3 Size of fixture supply (Table 604.5)

The minimum size of a fixture supply pipe follows Table 604.5. The fixture supply pipe must terminate

not more than 30 inches (762 mm) from the point of connection to the fixture; a reduced-size flexible

water connector installed between the supply pipe and the fixture must be of an approved type, and the

supply pipe must extend to the floor or wall adjacent to the fixture. The minimum size of individual

distribution lines used in gridded or parallel water distribution systems also follows Table 604.5

(IPC 2024, 604.5).

Where the developed length of the distribution line is 50 feet or less and the available pressure at

the meter is 35 psi or greater, the minimum size of an individual distribution line supplied from a

manifold and installed as part of a parallel water distribution system may be one nominal tube size

smaller than the sizes indicated (IPC 2024, Table 604.5, footnote a).

4.4 Pressure, flow control and manifolds

Where street water main pressures fluctuate, the building water distribution system must be designed

for the minimum pressure available (IPC 2024, 604.6). Wherever the pressure from the street main or

other source is insufficient to provide the flow pressures at fixture outlets required by Table 604.3,

a water pressure booster system conforming to Section 606.5 must be installed on the building water

supply system (IPC 2024, 604.7).

Where water pressure within a building exceeds 80 psi (552 kPa) static, an approved water

pressure-reducing valve conforming to ASSE 1003 or CSA B356 with strainer must be installed to reduce

the pressure in the building water distribution piping to not greater than 80 psi (552 kPa) static.

The exception covers service lines to sill cocks and outside hydrants, and main supply risers where

pressure from the mains is reduced to 80 psi (552 kPa) or less at individual fixtures (IPC 2024,

604.8). The valve must be designed to remain open to permit uninterrupted water flow in case of valve

failure (IPC 2024, 604.8.1), and valves, regulators and strainers must be constructed and installed so

that parts can be repaired or removed without breaking a pipeline or removing the valve and strainer

from the pipeline (IPC 2024, 604.8.2).

The flow velocity of the distribution system must be controlled to reduce the possibility of water

hammer; a water-hammer arrestor must be installed where quick-closing valves are used, installed in

accordance with the manufacturer's instructions, and must conform to ASSE 1010 (IPC 2024, 604.9).

Hot and cold water manifolds installed with gridded or parallel connected individual distribution

lines to each fixture or fixture fitting must be sized in accordance with Table 604.10.1, where the

total gallons per minute is the demand of all outlets supplied (IPC 2024, 604.10.1).

Individual fixture shutoff valves installed at the manifold must be identified as to the fixture

being supplied (IPC 2024, 604.10.2), and access must be provided to manifolds with integral factory-

or field-installed valves (IPC 2024, 604.10.3). Individual pressure balancing in-line valves for

individual fixture fittings must comply with ASSE 1066, must be installed in a location with access,

and must not be used alone as a substitute for the balanced pressure, thermostatic or combination

shower valves required in Section 412.3 (IPC 2024, 604.11).

5. Materials, joints and valves

Installation of a water service or water distribution pipe is prohibited in soil and ground water

contaminated with solvents, fuels, organic compounds or other detrimental materials causing

permeation, corrosion, degradation or structural failure of the piping material; where detrimental

conditions are suspected, a chemical analysis of the soil and ground water is required, and where

detrimental conditions exist, approved alternative materials or routing are required (IPC 2024,

605.1).

Pipe and pipe fittings, including valves and faucets, used in the water supply system must have not

more than 8 percent lead content (IPC 2024, 605.2). Pipe, fittings, joints, valves, faucets and

fixture fittings used to supply water for drinking or cooking purposes must comply with NSF 372 and

must have a weighted average lead content of 0.25 percent or less (IPC 2024, 605.2.1).

Fittings must be approved for installation with the piping material installed and comply with the

applicable standards listed in Table 605.5; fittings used in water supply systems must also comply

with NSF 61, and ductile and gray iron pipe and fittings used in water service piping systems must be

cement mortar lined in accordance with AWWA C104/A21.4 (IPC 2024, 605.5). Flexible water connectors

exposed to continuous pressure must conform to ASME A112.18.6/CSA B125.6, and access must be provided

to all flexible water connectors (IPC 2024, 605.6). Valves must be compatible with the type of piping

material installed in the system, conform to one of the standards listed in Table 605.7 or be

approved, and, where intended to supply drinking water, meet NSF 61 (IPC 2024, 605.7). Manufactured

pipe nipples must conform to one of the standards listed in Table 605.8 (copper, copper alloy and

chromium-plated: ASTM B687; steel: ASTM A733) (IPC 2024, 605.8).

Prohibited joints and connections in the water supply system are: cement or concrete joints; joints

made with fittings not approved for the specific installation; solvent-cement joints between

different types of plastic pipe; and saddle-type fittings (IPC 2024, 605.9).

6. Installation: valves, boosters, tanks and testing

Full-open valves must be installed in these locations (IPC 2024, 606.1):

buildings three stories or less in height where a common water supply piping system supplies other

than one- and two-family dwellings, a main shutoff valve must be provided for each tenant.

occupancies that are two stories or less in height and in one- and two-family residential

occupancies.

occupancies.

fixture equipped with individual stops.

Shutoff valves must be installed on the fixture supply to each plumbing fixture other than bathtubs

and showers in one- and two-family residential occupancies and other than in individual dwelling or

sleeping units that are provided with unit shutoff valves in hotels, motels, boarding houses and

similar occupancies; on the water supply pipe to each sill cock; and on the water supply pipe to each

appliance or mechanical equipment (IPC 2024, 606.2). Access must be provided to all full-open valves

and shutoff valves (IPC 2024, 606.3). Service and hose bibb valves must be identified, and other

valves installed in locations that are not adjacent to the fixture or appliance must be identified

as to the fixture or appliance served (IPC 2024, 606.4).

Where the water pressure in the public water main or individual water supply system is insufficient

to supply the minimum pressures and quantities specified in the code, the supply must be supplemented

by an elevated water tank, a hydropneumatic pressure booster system or a water pressure booster pump

installed in accordance with Section 606.5.5 (IPC 2024, 606.5.1). Within a booster system: a

low-pressure cutoff must be installed on all booster pumps to prevent creation of a vacuum or negative

pressure on the suction side of the pump when a positive pressure of 10 psi (68.94 kPa) or less occurs

on the suction side (IPC 2024, 606.5.5); potable water inlets to gravity tanks must be controlled by a

fill valve or other automatic supply valve installed so as to prevent the tank from overflowing, with

the inlet terminated to provide an air gap not less than 4 inches (102 mm) above the overflow

(IPC 2024, 606.5.6); and every pressure tank in a hydropneumatic pressure booster system must be

protected with a pressure relief valve set at a maximum pressure equal to the rating of the tank,

installed on the supply pipe to the tank or on the tank, discharging by gravity to a safe place of

disposal (IPC 2024, 606.5.10).

Water supply tanks must be covered to keep out unauthorized persons, dirt and vermin; the covers of

gravity tanks must be vented with a return bend vent pipe with an area not less than the area of the

down-feed riser pipe, screened with a corrosion-resistant screen of not less than 16 by 20 mesh per

inch (IPC 2024, 606.5.3). A gravity or suction water supply tank must have an overflow sized by

Table 606.5.4, discharging not less than 6 inches (152 mm) above the roof or roof drain, floor or

floor drain, or over an open water-supplied fixture, and covered with a corrosion-resistant screen of

not less than 16 by 20 mesh per inch and by 1/4-inch (6.4 mm) hardware cloth or terminating in a

horizontal angle seat check valve (IPC 2024, 606.5.4).

A drain pipe with a valve must be provided at the lowest point of each tank to permit emptying, must

discharge as required for overflow pipes, and must be not smaller than Table 606.5.7 (IPC 2024,

606.5.7).

Potable water gravity tanks or manholes of potable water pressure tanks must not be located directly

under any soil or waste piping or any source of contamination (IPC 2024, 606.5.8). Water pressure

tanks must be provided with a vacuum relief valve at the top of the tank operating up to a maximum

water pressure of 200 psi (1380 kPa) and up to a maximum temperature of 200°F (93°C), not less than

1/2 inch (12.7 mm) in size; the section does not apply to pressurized captive air

diaphragm/bladder tanks (IPC 2024, 606.5.9).

Testing: upon completion of a section of or the entire water supply system, the system or portion

completed must be tested in accordance with Section 312 (IPC 2024, 606.6). Section 312.6 requires the

system to be tested and proved tight under a water pressure not less than the working pressure of the

system, or — for piping systems other than plastic — by an air test of not less than 50 psi

(344 kPa), with the pressure held for not less than 15 minutes, and the water used for tests obtained

from a potable source (IPC 2024, 312.6).

7. Hot water supply system

In residential occupancies, hot water must be supplied to plumbing fixtures and equipment used for

bathing, washing, culinary purposes, cleansing, laundry or building maintenance; in nonresidential

occupancies, hot water must be supplied for culinary, cleansing, laundry or building maintenance

purposes, and hot water or tempered water must be supplied for bathing and washing purposes

(IPC 2024, 607.1). A thermostat control for a water heater serves as the temperature limiting means

only where the water heater complies with ASSE 1082 or ASSE 1085 (IPC 2024, 607.1.1). Tempered water

must be controlled by a limiting device conforming to ASSE 1070/ASME A112.1070/CSA B125.70 and set to

not greater than 110°F (43°C), by a thermostatic mixing valve conforming to ASSE 1017, by a water

heater conforming to ASSE 1082, or by a water heater conforming to ASSE 1084; this does not supersede

the requirement for protective shower valves in accordance with Section 412.3 (IPC 2024, 607.1.2).

The developed length of hot or tempered water piping, from the source of hot water to the fixtures

that require hot or tempered water, must not exceed 50 feet (15 240 mm); recirculating system piping

and heat-traced piping are considered sources of hot or tempered water (IPC 2024, 607.2). Where a

storage water heater is supplied with cold water that passes through a check valve, pressure reducing

valve or backflow preventer, a thermal expansion control device must be connected to the water heater

cold water supply pipe at a point downstream of all check valves, pressure reducing valves and

backflow preventers; thermal expansion tanks must be sized per the tank manufacturer's instructions

and such that the pressure in the water distribution system does not exceed that required by

Section 604.8 (IPC 2024, 607.3). Fixture fittings, faucets and diverters must be installed and adjusted

so that the flow of hot water from the fittings corresponds to the left-hand side of the fixture

fitting, with an exception for shower and tub/shower mixing valves conforming to

ASSE 1016/ASME A112.1016/CSA B125.16 or ASME A112.18.1/CSA B125.1 where the flow of hot water

corresponds to the markings on the device (IPC 2024, 607.4).

8. Protection of the potable water supply

A potable water supply system must be designed, installed and maintained so as to prevent

contamination from nonpotable liquids, solids or gases being introduced into the potable water supply

through cross connections or any other piping connections to the system; backflow preventer

applications must conform to Table 608.1, except as specifically stated in Sections 608.2 through

608.17.10 (IPC 2024, 608.1).

Table 608.1 (application of backflow preventers) — selected devices, degree of hazard, application and

standard:

In Table 608.1, "low hazard" is pollution and "high hazard" is contamination, both as defined in

Section 202 (IPC 2024, Table 608.1, footnotes a and b).

8.1 Means of protection

The minimum required air gap is measured vertically from the lowest end of a potable water outlet to

the flood level rim of the fixture or receptacle into which the outlet discharges; air gaps must

comply with ASME A112.1.2 and air gap fittings with ASME A112.1.3, and products listed and labeled to

those standards are considered in compliance (IPC 2024, 608.14.1).

Reduced pressure principle backflow prevention assemblies must conform to ASSE 1013, AWWA C511,

CSA B64.4 or CSA B64.4.1, and reduced pressure detector assembly backflow preventers to ASSE 1047;

they may be installed where subject to continuous pressure, and the relief opening must discharge by

air gap and be prevented from being submerged (IPC 2024, 608.14.2). Backflow preventers with

intermediate atmospheric vents must conform to ASSE 1012, ASSE 1081 or CSA B64.3, may be installed

under continuous pressure, and their relief opening must discharge by air gap and be prevented from

being submerged (IPC 2024, 608.14.3). Barometric loops must precede the point of connection and extend

vertically to a height of 35 feet (10 668 mm), and may be used only as an atmospheric-type or

pressure-type vacuum breaker (IPC 2024, 608.14.4). Pressure vacuum breaker assemblies must comply with

ASSE 1020 or CSA B64.1.2, spill-resistant vacuum breaker assemblies with ASSE 1056 or CSA B64.1.3, and

these assemblies must be installed with the critical level located not less than 12 inches (305 mm)

above all downstream piping and outlets; pressure vacuum breaker assemblies must not be installed

where spillage could cause damage to the structure (IPC 2024, 608.14.5). Double check backflow

prevention assemblies must conform to ASSE 1015, CSA B64.5, CSA B64.5.1 or AWWA C510, double check

detector fire protection assemblies to ASSE 1048, and these assemblies must be capable of operating

under continuous pressure conditions (IPC 2024, 608.14.7). Dual check backflow preventers must comply

with ASSE 1024 or CSA B64.6 (IPC 2024, 608.14.9), and backflow devices for chemical dispensers must

comply with ASSE 1055 or be equipped with an air gap fitting (IPC 2024, 608.14.8).

Access must be provided to backflow preventers as specified by the manufacturer's instructions

(IPC 2024, 608.15). They must not be located in areas subject to freezing except where they can be

removed by means of unions or are protected from freezing by heat, insulation or both (IPC 2024,

608.15.2), and the termination of piping from the relief port or air gap fitting must discharge to an

approved indirect waste receptor or to the outdoors where it will not cause damage or create a

nuisance, with the receptor and drainage piping sized to drain the maximum discharge flow rate from

the relief port as published by the manufacturer (IPC 2024, 608.15.2.1).

8.2 Protection of potable water outlets

Openings and outlets must be protected by an air gap between the opening and the fixture flood level

rim as specified in Table 608.16.1; openings and outlets equipped for hose connection must be

protected by means other than an air gap (IPC 2024, 608.16.1).

The "away from a wall" column applies where walls or obstructions are spaced from the nearest

inside-edge of the spout opening a distance greater than three times the diameter of the effective

opening for a single wall, or greater than four times the diameter of the effective opening for two

intersecting walls (IPC 2024, Table 608.16.1, footnote a).

Where openings and outlets are protected by vacuum breakers, the critical level of the vacuum breaker

must be set not less than 6 inches (152 mm) above the flood level rim of the fixture or device; fill

valves must be set in accordance with Section 415.3.1; vacuum breakers must not be installed under

exhaust hoods or similar locations that will contain toxic fumes or vapors; and pipe-applied vacuum

breakers must be installed not less than 6 inches (152 mm) above the flood level rim of the fixture,

receptor or device served (IPC 2024, 608.16.4). Approved deck-mounted or equipment-mounted vacuum

breakers, and faucets with integral atmospheric vacuum breakers or spill-resistant vacuum breaker

assemblies, must be installed in accordance with the manufacturer's instructions and the requirements

for labeling, with the critical level not less than 1 inch (25 mm) above the flood level rim

(IPC 2024, 608.16.4.1). Sill cocks, hose bibbs, wall hydrants and other openings with a hose

connection must be protected by an atmospheric-type or pressure-type vacuum breaker or a permanently

attached hose connection vacuum breaker, except for water heater and boiler drain valves with hose

connection threads intended only for tank or vessel draining, and water supply valves intended for

connection of clothes washing machines where backflow prevention is otherwise provided or integral

with the machine (IPC 2024, 608.16.4.2).

8.3 Health care plumbing (highlights)

Health care plumbing systems must conform to Section 609 in addition to the other requirements of the

code, and the provisions apply to Group I-1, Group I-2, ambulatory care facilities, medical offices,

research and testing laboratories, and Group F facilities manufacturing pharmaceutical drugs and

medicines (IPC 2024, 609.1). Group I-2, Condition 2 facilities must have not fewer than two water

service pipes sized so that, with the loss of the largest service pipe, the remaining service pipes

meet the water demand for the entire facility, each service with a shutoff valve in the building and a

shutoff valve at the utility-provided point of connection (IPC 2024, 609.2). Vacuum breakers in health

care plumbing must be installed not less than 6 inches (152 mm) above the flood level rim of the

fixture or device in accordance with Section 608, and the flood level rim of hose connections is the

maximum height at which any hose is utilized (IPC 2024, 609.4).

9. Disinfection and treatment

New potable water systems must be purged of deleterious matter and disinfected prior to utilization.

The method is that prescribed by the health authority or water purveyor having jurisdiction or, in the

absence of a prescribed method, the procedure described in AWWA C651 or AWWA C652 or in Section 610;

the requirement applies to on-site or in-plant fabrication of a system or of a modular portion of a

system (IPC 2024, 610.1). The procedure published in the section is: flush the pipe system with clean,

potable water until dirty water does not appear at the points of outlet; fill the system or part with

a water/chlorine solution containing not less than 50 parts per million (50 mg/L) of chlorine, valve

it off and let it stand for 24 hours, or fill with a solution containing not less than 200 parts per

million (200 mg/L) of chlorine and let it stand for 3 hours; then flush with clean potable water until

the chlorine is purged; and repeat the procedure where a bacteriological examination shows

contamination remains (IPC 2024, 610.1, items 1 through 4).

Point-of-use reverse osmosis drinking water treatment units must comply with CSA B483.1 or NSF 58, and

drinking water treatment units must meet CSA B483.1, NSF 42, NSF 44, NSF 53 or NSF 62 (IPC 2024,

611.1). The discharge from a reverse osmosis drinking water treatment unit must enter the drainage

system through an air gap or an air gap device meeting CSA B483.1 or NSF 58 (IPC 2024, 611.2), and

tubing to and from drinking water treatment units must be of a size and material recommended by the

manufacturer and comply with NSF 14, NSF 42, NSF 44, NSF 53, NSF 58 or NSF 61 (IPC 2024, 611.3).

Solar systems for domestic hot water heating and similar uses must be constructed and installed in

accordance with the International Mechanical Code (IPC 2024, 612.1). Temperature-actuated mixing

valves installed to reduce water temperatures to defined limits must comply with ASSE 1017 and be

installed at the hot water source (IPC 2024, 613.1).

Protection of the Potable Water Supply (Backflow Prevention)

Reference text for the backflow prevention area. Every rule below is written from the printed line of

the 2024 International Plumbing Code (IPC 2024) that carries it, and each rule names the section it

comes from. Where the printed line does not state a value, no value is stated here. The degree of

hazard a device may be used on, the applications it may serve and the sizes it is made in are the

values carried by Table 608.1; they are reproduced here as that table prints them.

1. The duty this area carries

A potable water supply system must be designed, installed and maintained in a way that prevents

contamination from nonpotable liquids, solids or gases being introduced into the potable supply

through cross connections or through any other piping connection to the system. The applications of

backflow preventers follow Table 608.1, except where Sections 608.2 through 608.17.10 state the

protection specifically (IPC 2024, 608.1). That whole-chapter duty is what the rest of this text

unpacks: the table is the default answer, and the numbered sections are the particular answers that

override it.

Cross connections are prohibited outright, and the only way to keep one is to install approved

backflow prevention assemblies, backflow prevention devices, or other approved means or methods that

protect the potable supply (IPC 2024, 608.7). Where a private water supply exists alongside a potable

public supply, a cross connection between the two is prohibited without qualification (IPC 2024,

608.7.1).

2. Where the plumbing system may not go at all

Service utilities are held back until the code official authorizes them: a person may not connect a

utility, source of energy, fuel, power, water system or sewer system to a building or system

regulated by the code and requiring a permit until that authorization exists (IPC 2024, 109.1).

The code official may authorize a temporary connection of the building or system to the utility,

source of energy, fuel, power, water system or sewer system for testing plumbing systems or for use

under a temporary approval (IPC 2024, 109.2), and may authorize disconnection of utility service to a

building, structure or system regulated by the code and the referenced codes and standards in an

emergency where disconnection is necessary to eliminate an immediate hazard to life or property, or

where the utility connection was made without the approval Sections 109.1 and 109.2 require (IPC 2024,

109.3). Where the disconnection decision is made, the code official must notify the serving utility

and, wherever possible, the owner, the owner's authorized agent and the occupant before acting; where

that was not possible beforehand, the notice must be given in writing as soon as is practical

afterward (IPC 2024, 109.3).

Plumbing systems may not be located in an elevator shaft or in an elevator equipment room. Floor

drains, sumps and sump pumps are permitted at the base of the shaft, but only where they are

indirectly connected to the plumbing system and comply with Section 1003.4 (IPC 2024, 301.6).

Together those two provisions decide where a potable supply may be brought in and where it may be

left: a plumbing system is not permitted inside the shaft, and the drainage that is permitted at the

base of the shaft is kept at arm's length from the supply by the indirect connection.

3. The device table: hazard, application and sizes (Table 608.1)

Table 608.1 sorts the available protections into backflow prevention assemblies, backflow preventer

plumbing devices, and other means or methods, and for each one prints the degree of hazard it may

serve, the application (backsiphonage only, backpressure, or both) and the sizes or standards that

apply.

The table's footnotes tie the two words "low hazard" and "high hazard" back to the definitions of

pollution and contamination in the code's definition chapter, and the application column's "low head

backpressure" and "backsiphonage" to the definitions of backflow in the same place (IPC 2024, Table

608.1). Reading the table therefore means reading those definitions first: a device is not selected

because the pipe is small, but because the hazard on the other side of the connection is a pollution

or a contamination and because the driving force is backpressure or backsiphonage.

4. What the assembly has to be, and where it may sit

The means of protection are given standards, and those standards are what an installer orders against

and what an inspector reads off the device.

water outlet to the flood level rim of the fixture or receptacle the outlet discharges into. Air

gaps must comply with ASME A112.1.2 and air gap fittings with ASME A112.1.3; a product listed and

labeled to either standard is treated as complying (IPC 2024, 608.14.1).

CSA B64.4.1, and reduced pressure detector assemblies to ASSE 1047. They may be installed where the

device is subject to continuous pressure conditions, and the relief opening must discharge by air

gap and must be kept from being submerged (IPC 2024, 608.14.2).

1081 or CSA B64.3, may be installed under continuous pressure conditions, and their relief opening

must discharge by air gap and must not be submerged (IPC 2024, 608.14.3).

height of 35 feet (10 668 mm). It may only be used as an atmospheric-type or pressure-type vacuum

breaker (IPC 2024, 608.14.4).

spill-resistant vacuum breaker assemblies with ASSE 1056 or CSA B64.1.3. The critical level of the

assembly must sit not less than 12 inches (305 mm) above all downstream piping and outlets, and a

pressure vacuum breaker assembly may not be installed where spillage could damage the structure

(IPC 2024, 608.14.5).

ASSE 1001 or CSA B64.1.1; hose-connection vacuum breakers to ASME A112.21.3, ASSE 1011, ASSE 1019,

ASSE 1035, ASSE 1052, CSA B64.2, CSA B64.2.1, CSA B64.2.1.1, CSA B64.2.2 or CSA B64.7. They operate

under normal atmospheric pressure when the critical level is installed at the required height

(IPC 2024, 608.14.6).

double check detector fire protection assemblies to ASSE 1048. They must be capable of operating

under continuous pressure conditions (IPC 2024, 608.14.7).

1055 or be equipped with an air gap fitting (IPC 2024, 608.14.8).

Access must be provided to backflow preventers as the manufacturer's instructions specify (IPC 2024,

608.15), and outdoor enclosures for backflow prevention devices must comply with ASSE 1060 (IPC 2024,

608.15.1).

Placement is a rule of its own: a backflow preventer may not be located in an area subject to

freezing, unless it can be removed by means of unions or is protected from freezing by heat,

insulation, or both (IPC 2024, 608.15.2). Where the piping from the relief port or air gap fitting of

a backflow preventer terminates, it must discharge to an approved indirect waste receptor or to the

outdoors where it will not cause damage or create a nuisance, and both the waste receptor and the

drainage piping must be sized to drain the maximum discharge flow rate from the relief port as the

backflow preventer manufacturer publishes it (IPC 2024, 608.15.2.1). A discharge that is merely

"allowed to drip somewhere" is not the rule: the receiving pipe has to be able to take the device's

own published maximum flow.

5. Protection of openings and outlets (608.16)

Potable water openings and outlets are protected under one of six provisions — air gap, reduced

pressure principle assembly, backflow preventer with intermediate atmospheric vent, or one of the

three vacuum breaker provisions (IPC 2024, 608.16).

Protection by air gap means an air gap between the opening and the fixture flood level rim as Table

608.16.1 specifies. An opening or outlet equipped for hose connection must be protected by means

other than an air gap (IPC 2024, 608.16.1).

TABLE 608.16.1 MINIMUM REQUIRED AIR GAPS

For that table, "away from a wall" applies where walls or obstructions are spaced from the nearest

inside edge of the spout opening by more than three times the diameter of the effective opening for a

single wall, or more than four times that diameter for two intersecting walls (IPC 2024, Table

608.16.1).

The other routes to protecting an opening or outlet are: a reduced pressure principle backflow

prevention assembly, or a reduced pressure principle fire protection backflow prevention assembly, on

potable water supplies (IPC 2024, 608.16.2); a backflow preventer with an intermediate atmospheric

vent (IPC 2024, 608.16.3); or a vacuum breaker (IPC 2024, 608.16.4).

The vacuum breaker provision carries the heights and the prohibitions an installer works to. The

critical level of the vacuum breaker must be set not less than 6 inches (152 mm) above the flood level

rim of the fixture or device, fill valves are set as the code's fill valve section directs, vacuum

breakers may not be installed under exhaust hoods or in similar locations that will contain toxic

fumes or vapors, and a pipe-applied vacuum breaker must be installed not less than 6 inches (152 mm)

above the flood level rim of the fixture, receptor or device served (IPC 2024, 608.16.4).

Deck-mounted and integral vacuum breakers have a shorter height of their own: approved deck-mounted or

equipment-mounted vacuum breakers, and faucets with integral atmospheric vacuum breakers or

spill-resistant vacuum breaker assemblies, are installed per the manufacturer's instructions and per

the labeling requirements, with the critical level not less than 1 inch (25 mm) above the flood level

rim (IPC 2024, 608.16.4.1).

Hose connections — sill cocks, hose bibbs, wall hydrants and other openings with a hose connection —

are protected by an atmospheric-type or pressure-type vacuum breaker, or by a permanently attached

hose connection vacuum breaker. Two connections are carved out of that rule: water heater and boiler

drain valves with hose connection threads that are intended only for tank or vessel draining, and

water supply valves intended for connecting clothes washing machines where backflow prevention is

otherwise provided or is integral with the machine (IPC 2024, 608.16.4.2).

6. Connections to the potable system, appliance by appliance (608.17)

The chapter then names the equipment that commonly gets connected to potable water and fixes the

protection for each:

A carbonated beverage dispenser is protected by a backflow preventer conforming to ASSE 1022 or by

an air gap, and no part of the device downstream from its second check valve, nor the piping

downstream of that, may be affected by carbon dioxide gas (IPC 2024, 608.17.1.1). Coffee machines

and noncarbonated drink dispensers are protected by a backflow preventer conforming to ASSE 1022,

ASSE 1024 or ASSE 1032, or by an air gap (IPC 2024, 608.17.1.2).

atmospheric vent complying with ASSE 1012, ASSE 1081 or CSA B64.3; where conditioning chemicals are

put into the system, the potable connection is protected by an air gap or a reduced pressure

principle backflow preventer complying with ASSE 1013, AWWA C511 or CSA B64.4 (IPC 2024, 608.17.2).

potable water by double-wall construction, with an air gap open to the atmosphere between the two

walls; an essentially nontoxic transfer fluid permits single-wall construction (IPC 2024, 608.17.3).

backflow prevention assembly, a double check fire protection backflow prevention assembly, or a

reduced pressure principle fire protection backflow prevention assembly. Isolation of the water

supply system is not required where the systems are installed as part of the water distribution

system under the code and have no fire department connection, and isolation is not required for

deluge, preaction or dry pipe systems (IPC 2024, 608.17.4).

continuous pressure and contains chemical additives or antifreeze, or is connected to a nonpotable

secondary water supply, the potable supply is protected by a reduced pressure principle backflow

prevention assembly or a reduced pressure principle fire protection backflow prevention assembly;

where additives or antifreeze are added to only part of the system, that assembly may be located so

as to isolate that part. Where the system is not under continuous pressure, the protection is an

air gap or an atmospheric vacuum breaker conforming to ASSE 1001 or CSA B64.1.1 (IPC 2024,

608.17.4.1).

pressure vacuum breaker assembly or a reduced pressure principle backflow prevention assembly. No

valve may be installed downstream from an atmospheric vacuum breaker. Where chemicals are put into

the system, the protection must be a reduced pressure principle backflow prevention assembly

(IPC 2024, 608.17.5).

fixture, tank, vat, pump or other equipment subject to high-hazard backpressure, the connection is

protected by a reduced pressure principle backflow prevention assembly (IPC 2024, 608.17.6).

the means listed for it: for chemical dispensers, the air gap, the reduced pressure principle

assembly, the pressure vacuum breaker assembly, the atmospheric-type vacuum breaker or the chemical

dispenser backflow device (IPC 2024, 608.17.7); for portable cleaning equipment, the air gap, the

reduced pressure principle assembly, the backflow preventer with intermediate atmospheric vent, the

double check assembly or the chemical dispenser backflow device (IPC 2024, 608.17.8); for dental

pumping equipment, the air gap, the reduced pressure principle assembly, the pressure vacuum

breaker assembly, the atmospheric-type vacuum breaker or the chemical dispenser backflow device

(IPC 2024, 608.17.9).

backflow preventer conforming to ASSE 1012 or by an air gap (IPC 2024, 608.17.10).

7. Fixtures, equipment and the water that serves them (608.2 through 608.13)

Plumbing fixtures. The supply lines and fittings for plumbing fixtures are installed so as to prevent

backflow, and plumbing fixture fittings provide backflow protection in accordance with ASME

A112.18.1/CSA B125.1 (IPC 2024, 608.2).

Devices, appurtenances, appliances and apparatus. Equipment intended to serve a special function —

sterilization, distillation, processing, cooling, or the storage of ice or foods — that connects to

the water supply system must be provided with protection against backflow and contamination of the

water supply system (IPC 2024, 608.3). For hospital fixtures the water supply is protected by a

reduced pressure principle backflow prevention assembly, an atmospheric or spill-resistant vacuum

breaker assembly, or an air gap; vacuum breakers for bedpan washer hoses must be not less than 5 feet

(1524 mm) above the floor, and vacuum breakers for hose connections in health care or laboratory areas

not less than 6 feet (1829 mm) above the floor (IPC 2024, 608.3.1).

Potable water handling and treatment equipment. Water pumps, filters, softeners, tanks and other

appliances and devices that handle or treat potable water for the potable distribution system must be

located so that contamination cannot enter them, and the overflow, relief valve and waste discharge

pipes from them must terminate through an air gap (IPC 2024, 608.4). More generally, water pumps,

filters, softeners, tanks and other devices handling or treating potable water must be protected

against contamination (IPC 2024, 608.13).

Water service piping is protected under the code's water service provisions (IPC 2024, 608.5).

Chemicals. Chemicals and other substances that would produce toxic conditions, taste, odor or

discoloration in a potable water system may not be introduced into or used in such systems (IPC 2024,

608.6).

Reuse and reutilization. Water used to heat or cool equipment or for other processes may not be

returned to the potable water system; it must be discharged into a drainage system through an air gap

or used for nonpotable purposes (IPC 2024, 608.10). Piping that has conveyed anything other than

potable water may not be used to convey potable water (IPC 2024, 608.11).

Tanks. Where a water tank, its interior coating or its liner is in contact with potable water intended

for drinking, those materials must conform to NSF 61, and the interior surface of the tank may not be

lined, painted or repaired with any material that changes the taste, odor, color or potability of the

water supply when the tank is placed in, or returned to, service (IPC 2024, 608.12).

Valves and outlets below grade. Potable water outlets and combination stop-and-waste valves may not be

installed underground or below grade, and a freezeproof yard hydrant that drains the riser into the

ground is treated as having a stop-and-waste valve below grade. Such a hydrant is permitted where the

potable supply to it is protected under the backflow provisions for reduced pressure principle

assemblies or pressure vacuum breaker assemblies, and the hydrants and the piping from the backflow

preventer to the hydrant are identified as the code's identification section requires (IPC 2024,

608.8).

8. Identifying what is not potable (608.9)

Where nonpotable water systems are installed, the piping conveying the nonpotable water must be

identified by color marking, metal tags or tape (IPC 2024, 608.9).

Signage. Nonpotable water outlets such as hose connections, open-ended pipes and faucets must carry

signage reading "Nonpotable water is utilized for [application name]. CAUTION: NONPOTABLE WATER – DO

NOT DRINK." The words must be legibly and indelibly printed on a tag or sign of corrosion-resistant

waterproof material, or indelibly printed on the fixture; the letters must be not less than 0.5 inch

(12.7 mm) in height and in colors contrasting with their background, and the required pictograph must

appear on the signage in addition to the wordage (IPC 2024, 608.9.1).

Pipe labeling. Nonpotable distribution piping must be purple and embossed, integrally stamped or

marked with "CAUTION: NONPOTABLE WATER – DO NOT DRINK", or installed with a purple identification tape

or wrap. The identification must carry the contents of the system and an arrow indicating direction of

flow, and hazardous systems must also state the nature of the hazard. The identification must be

repeated at intervals not exceeding 25 feet (7620 mm) and at every point where the piping passes

through a wall, floor or roof, and the lettering must be readily observable within the room or space

where the piping is located (IPC 2024, 608.9.2).

The color must be discernible and consistent throughout the building, and purple is the color for

reclaimed, rain and graywater distribution systems (IPC 2024, 608.9.2.1). The size of the background

color field and of the lettering follows Table 608.9.2.2 (IPC 2024, 608.9.2.2):

TABLE 608.9.2.2 SIZE OF PIPE IDENTIFICATION

Where identification tape is used, it must be not less than 3 inches (76 mm) wide, with white or

black lettering on a purple field stating "CAUTION: NONPOTABLE WATER – DO NOT DRINK". The tape is

installed on top of nonpotable rainwater distribution pipes, fastened not less than every 10 feet

(3048 mm) to each pipe length and run continuously along the entire length of the pipe (IPC 2024,

608.9.2.3).

9. Individual water supplies: keeping the source out of reach of contamination (608.18)

An individual water supply must be located and constructed so as to be safeguarded against

contamination (IPC 2024, 608.18).

Well location. A potable ground water source or pump suction line may not be located closer to

potential sources of contamination than the distances Table 608.18.1 shows, and where the underlying

rock is limestone or fragmented shale the local or state health department must be consulted on the

well site. Those distances are minimum separations, and they must be increased in areas of creviced

rock or limestone, or where ground water moves from sources of contamination toward the well

(IPC 2024, 608.18.1).

TABLE 608.18.1 DISTANCE FROM CONTAMINATION TO PRIVATE WATER SUPPLIES AND PUMP SUCTION LINES

Elevation and depth. Well sites must be positively drained and sit at higher elevations than

potential sources of contamination (IPC 2024, 608.18.2). A private potable well supply may not be

developed from a water table less than 10 feet (3048 mm) below the ground surface (IPC 2024,

608.18.3).

Casings and covers. Each well must have a watertight casing extending to not less than 10 feet

(3048 mm) below the ground surface, with the casing extending not less than 6 inches (152 mm) above

the well platform, large enough to permit a separate drop pipe, and sealed at the bottom in an

impermeable stratum or extended several feet into the water-bearing stratum (IPC 2024, 608.18.4).

Drilled or driven well casings must be of steel or another approved material; where a drilled well

extends into rock, the casing must extend to and set firmly in the formation, and the annular space

between earth and casing must be filled with cement grout to not less than 10 feet (3048 mm) below

the ground surface, or to the rock surface where the casing is set to rock (IPC 2024, 608.18.5). Dug

or bored well casings must be watertight concrete, tile, or galvanized or corrugated metal pipe

extending to not less than 10 feet (3048 mm) below ground — and below the water table where the table

is deeper than 10 feet — surrounded by 6 inches (152 mm) of grout poured between the casing and the

ground and extending not less than 10 feet (3048 mm) below ground (IPC 2024, 608.18.6). A potable

water well must have an overlapping watertight cover at the top of the casing or pipe sleeve so that

contaminated water and other substances cannot enter through the annular opening; covers must extend

downward not less than 2 inches (51 mm) over the outside of the casing or wall, a dug well cover must

carry a pipe sleeve that lets the pump suction pipe, cylinder or jet body be withdrawn without

disturbing the cover, and where pump sections or discharge pipes pass through the side of the casing

the circle of contact must be watertight (IPC 2024, 608.18.7).

Drainage. Wells and springs must be constructed so that surface drainage is diverted away from them

(IPC 2024, 608.18.8).

10. What the inspector reads on the drawing and in the field

Put together, the area answers five questions in a fixed order:

device, or other approved means or method (IPC 2024, 608.7).

from the definitions the table's footnotes point to (IPC 2024, Table 608.1).

column of the table, and the same distinction in Sections 608.16 and 608.17, rule out devices that

only hold against one of the two (IPC 2024, Table 608.1).

the installation rules add the height of the critical level (IPC 2024, 608.14.5), the clearance

from a flood level rim (IPC 2024, 608.16.4), the prohibition on freezing locations (IPC 2024,

608.15.2), and the requirement that the relief discharge be able to take the device's published

maximum flow (IPC 2024, 608.15.2.1).

Identification, signage, purple piping and repeat intervals are the answer (IPC 2024, 608.9).