After completing this chapter, you will be able to:
4.Identify the scope and application of the Georgia Plumbing Code for systems installation, including the hierarchy of code, standards, and manufacturer instructions.
5.Apply the correct minimum number of plumbing fixtures for a given occupancy classification using the code’s occupancy-based tables.
6.Distinguish between the three methods of sanitary drainage system sizing (fixture units, velocity, and slope) and perform basic calculations.
7.Explain the requirements for vent system installation, including vent termination, sizing, and the role of circuit and combination vents.
8.Recognize the special installation rules for indirect waste, backflow prevention, and interceptors.
9.Describe the master plumber’s responsibility for coordination, inspection, and testing of installed systems.
1.1 Scope and Application of the Code
The 2018 Georgia Plumbing Code is based on the 2018 International Plumbing Code (IPC) with Georgia amendments. For the master license exam, you must understand that the code applies to the installation, alteration, repair, and maintenance of plumbing systems, including piping, fixtures, and equipment. The code does not apply to the installation of gas piping (covered by the Georgia Gas Code) or to public water supply or sewer systems beyond the point of connection.
Key hierarchy for installation decisions:
14.The code itself (minimum requirements).
15.Referenced standards (ASTM, ASME, ASSE, etc.) — these are part of the code by reference.
16.Manufacturer installation instructions — must be followed where they exceed code minimums.
17.Georgia amendments — these override the base IPC where they differ.
Master-level responsibility: You are the licensed person of record. You must ensure that the system is installed per approved plans, that all required permits are obtained, and that the work is performed by registered journeymen under your supervision. The code holds you responsible for the final installation regardless of who performed the physical labor.
1.2 Fixture Counts and Occupancy Classifications
The minimum number of plumbing fixtures is found in IPC Chapter 29 (Tables 2902.1 and 2902.2). Georgia has not amended these tables significantly, but you must know how to read them.
Critical concepts:
Fixture counts are based on occupant load, not building area. The occupant load is determined by the building code (IBC), not the plumbing code. You must be able to calculate fixture counts from a given occupant load.
Separate facilities are required for each sex where the occupant load exceeds a threshold (typically 30 for assembly occupancies).
Unisex toilet rooms are permitted in certain occupancies and may reduce the total count, but the code requires that the remaining fixtures still meet the minimum for the occupancy.
Common exam trap: For assembly occupancies, the code uses a two-tier system: the first 1,000 occupants are counted at one rate, and additional occupants at a reduced rate. For example, for a theater, water closets are provided at 1 per 125 males for the first 1,000 and 1 per 250 thereafter. Candidates often apply the second rate to the entire population.
Table 2902.1 key occupancies to memorize (approximate values):
Assembly (theaters, churches): 1 WC per 125 males, 1 per 65 females; lavatories at 1 per 200.
Educational: 1 WC per 50 students (male and female combined counts differ).
Factory/Industrial: 1 WC per 100 employees.
Mercantile: 1 WC per 500 for males, 1 per 500 for females (but minimum 2 total).
Office: 1 WC per 40 for each sex (up to 100 occupants, then 1 per 50).
Service sinks: At least one service sink is required in all occupancies except one- and two-family dwellings.
1.3 Sanitary Drainage System Installation
1.3.1 Pipe Materials and Joints
IPC Chapter 7 covers sanitary drainage. Pipe materials must be approved for the application. Common approved materials:
Cast iron (hub and spigot, no-hub) — for above and below ground.
PVC (DWV) — schedule 40 for above ground; schedule 40 or SDR 35 for below ground (check Georgia amendments for burial depth restrictions).
ABS — where permitted by local amendment.
Copper (DWV) — for above ground only.
Joint requirements:
No-hub couplings must be listed and installed with torque wrench per manufacturer.
PVC joints must be solvent-cemented with listed primer and cement.
Transition joints between different materials (e.g., copper to cast iron) require a listed transition coupling.
Master-level point: The code requires that all drainage piping be clean and free from obstructions before final connection. You must also ensure that piping is protected from damage during construction — a common site failure.
1.3.2 Drainage System Sizing
Sizing is based on fixture units (FU). Each fixture has a drainage fixture unit value (Table 709.1). The total FU load is then converted to a pipe size using Table 710.1(1) for horizontal branches and Table 710.1(2) for stacks.
Key rules:
A horizontal branch is sized by the total FU discharging into it, but the pipe must not be smaller than the largest fixture drain connected.
A building drain (underground) is sized by total FU and slope. Slope must be ¼ inch per foot for pipes ≤ 3 inches, and ⅛ inch per foot for pipes ≥ 4 inches (unless otherwise approved).
A soil or waste stack is sized by the total FU and the number of branch intervals. A branch interval is a story height (typically 8–12 feet). The stack must be sized for the total load, but the upper portion may be smaller if only a few branches connect.
Velocity requirement: The code states that drainage piping must be sized so that the velocity is not less than 2 feet per second (fps) at full flow. This is a design check, not a table lookup. For exam purposes, know that a 4-inch pipe at ⅛ inch per foot slope carries approximately 180 FU, but the actual flow velocity must be verified for long runs.
Common exam trap: Do not confuse drainage fixture units with water supply fixture units (Chapter 6). They are different values. A 1½-inch lavatory drain is 1 FU, but its water supply is 1.0 WSFU (hot and cold combined).
1.3.3 Slope and Support
Horizontal drainage pipes must be installed in uniform alignment at a slope of ¼ inch per foot for 3-inch and smaller; ⅛ inch per foot for 4-inch and larger.
Pipes must be supported at intervals per Table 308.5 (e.g., PVC horizontal: every 4 feet for 1¼-inch and smaller, every 4 feet for 1½-inch, and every 4 feet for 2-inch and larger — actually PVC is every 4 feet regardless of size; cast iron is every 5 feet for horizontal, 10 feet for vertical).
Vertical pipes must be supported at each floor level, but not more than 15 feet apart for cast iron, 10 feet for PVC.
1.4 Vent System Installation
1.4.1 Vent Types and Purpose
Vents protect trap seals by equalizing pressure. The code (IPC Chapter 9) recognizes several vent types:
Individual vent — connects to the fixture drain behind the trap.
Common vent — serves two fixtures on the same floor, connecting at the junction of the two fixture drains.
Circuit vent — serves up to eight fixtures on a horizontal branch, connecting upstream of the last fixture.
Combination vent — a circuit vent that also serves as a relief vent.
Wet vent — a vent that also carries drainage from another fixture (limited to certain fixtures and loads).
1.4.2 Vent Sizing
Vent size is based on the developed length (total length from the vent connection to the vent terminal) and the total FU connected to the vent. Use Table 916.1 (vent pipe sizing). The vent must be at least 1¼ inches in diameter (or ½ the drain size, whichever is larger).
Key rule: The vent must connect to the drain within a certain distance from the trap weir. For a 1¼-inch trap, the maximum distance is 2 feet 6 inches; for 1½-inch, 3 feet 6 inches; for 2-inch, 5 feet; for 3-inch, 6 feet; for 4-inch, 10 feet. This distance is measured along the fixture drain from the trap weir to the vent connection.
Common exam trap: The vent connection must be above the centerline of the horizontal drain (or at 45° above horizontal). A connection below the centerline turns the vent into a drain.
1.4.3 Vent Termination
Vents must terminate not less than 6 inches above the roof (measured from the roof surface to the vent opening), and at least 1 foot from any vertical wall.
Vents must not terminate within 10 feet of a window, door, or air intake unless they are at least 2 feet above the opening.
Vent caps are required to prevent birds and debris from entering.
Special case — vent through a wall: In Georgia, vents may terminate through a wall only if the code specifically permits it (e.g., for certain island fixtures). Generally, roof termination is required.
1.5 Indirect Wastes and Special Wastes
1.5.1 Indirect Waste Requirements
IPC Chapter 8 requires that certain fixtures and appliances discharge through an air gap or air break into a receptor (floor drain, standpipe, or receptor sink). Examples:
Dishwashers (air gap or high loop per manufacturer).
Food waste disposers (may connect directly to the drain with a wye).
Commercial dishwashers, ice machines, and beverage dispensers — must discharge indirectly.
All equipment that processes food or drink must have an indirect connection to prevent backflow.
Receptor requirements: The receptor must be accessible, and the air gap must be at least 2 pipe diameters (but not less than 1 inch) above the flood rim of the receptor.
1.5.2 Interceptors and Separators
Interceptors are required for:
Grease (commercial kitchens) — sized per local requirements or manufacturer.
Oil and flammable liquids (garages) — oil interceptors.
Sand and sediment (car washes) — sand interceptors.
Master-level point: Interceptors must be accessible for cleaning. The code prohibits connecting a grease interceptor to a sanitary drain without a separate vent. The interceptor vent must be independent of the fixture vents.
1.6 Backflow Prevention and Cross-Connection Control
IPC Chapter 6 (water supply) requires protection of the potable water supply. The master plumber must know the five levels of protection:
99.Air gap — the highest level; a physical separation between the supply and the receiving vessel.
100.Reduced pressure principle backflow preventer (RPZ) — for high-hazard connections.
101.Double check valve assembly (DCVA) — for low-hazard connections.
102.Atmospheric vacuum breaker (AVB) — for hose connections and certain fixtures.
103.Spill-resistant vacuum breaker — for continuous pressure applications.
Where each is required:
All fixtures with hose threads (sinks, laundry) require a vacuum breaker.
Boilers, cooling towers, and irrigation systems require an RPZ or DCVA per the hazard.
Residential — the water heater requires a temperature and pressure relief valve, but not a backflow preventer (unless the local jurisdiction requires it).
Exam trap: An AVB cannot be installed under continuous pressure (i.e., it must be on the downstream side of a shutoff valve). An RPZ must be tested annually and installed with test cocks accessible.
1.7 Testing and Inspection
IPC Chapter 3 (general regulations) requires that all piping be tested before being concealed. The master plumber is responsible for scheduling and witnessing tests.
Test requirements:
Drainage and vent: Water test — fill the system with water to the highest point (or 10 feet of head) and maintain for 15 minutes without leakage. Alternatively, an air test at 5 psi for 15 minutes is permitted.
Water supply: Hydrostatic test at 1.5 times the working pressure (but not less than 100 psi) for 2 hours.
Gas piping (per Georgia Gas Code): Air test at 10 psi for 15 minutes, then a soap-and-water test at operating pressure.
Final inspection: The master must verify that all fixtures are set level, properly sealed, and that the system functions without leaks. The code requires that the building drain be tested before backfilling.
1.8 Code Navigation
For the closed-book exam, you must know where to find concepts quickly. Use this mental map:
Topic
Code Location
Fixture counts
IPC Chapter 29, Tables 2902.1, 2902.2
Drainage materials
IPC Chapter 7, Section 702
Drainage sizing tables
IPC Tables 709.1, 710.1(1), 710.1(2)
Slope requirements
IPC Section 704.1
Pipe supports
IPC Table 308.5
Vent types
IPC Chapter 9, Sections 905–909
Vent sizing
IPC Table 916.1
Vent termination
IPC Section 903
Indirect waste
IPC Chapter 8, Sections 801–803
Interceptors
IPC Section 1003
Backflow prevention
IPC Chapter 6, Section 608
Testing
IPC Chapter 3, Section 312
Water supply sizing
IPC Chapter 6, Tables 603.1, 604.5
1.9 Practical Field Points for the Master Plumber
123.Coordination with other trades: The master plumber must coordinate sleeve placement, fire-stopping, and rough-in dimensions with the general contractor. A common failure is missing fire-stop around pipes penetrating rated walls.
124.As-built documentation: You are responsible for marking changes from the approved plans. The code requires that the permit holder keep a set of approved plans on site.
125.Fixture rough-in heights: While not in the code, standard heights (WC rough-in at 12 inches from finished wall to center of flange; lavatory supply at 20 inches AFF) are expected by inspectors. Know these from practice.
126.Water heater installation: The code requires a pan and drain for water heaters in attics or above finished spaces. The T&P relief valve must discharge within 6 inches of the floor or to a drain.
127.Final responsibility: The master plumber must sign the certificate of completion for the permit. If a journeyman under your supervision makes an error, you own it. Conduct your own walkthrough before calling for inspection.
1.10 Common Exam Traps Summary
Fixture unit confusion: Drainage FU ≠ water supply WSFU. Always check which table you are using.
Slope direction: The code requires uniform slope; a pipe that sags or has a belly is a violation even if the average slope is correct.
Vent connection distance: Measured from the trap weir, not from the fixture outlet.
Air gap measurement: Measured from the supply outlet to the flood rim of the receptor, not to the bottom of the receptor.
Test duration: Water test for drainage is 15 minutes; water supply test is 2 hours. Do not swap these.
Georgia amendments: The state may have stricter requirements for backflow (e.g., mandatory RPZ on all irrigation). Always check the amendment section at the front of the code.
Summary
Systems installation is the core of the master plumber’s daily responsibility. You must know the code’s minimum requirements for fixtures, drainage, vents, and backflow protection, and you must be able to apply them to real-world conditions. The exam will test your ability to navigate the code structure and apply tables correctly. Master the tables in Chapter 29 (fixtures), Chapter 7 (drainage), Chapter 9 (vents), and Chapter 6 (water supply), and you will be well prepared for the systems installation portion of the Georgia Master Plumber exam.
