IPC - International Plumbing Code Water Supply and Distribution 2 — Questions and Answers
Question 1: According to the IPC, which of the following pipe materials is NOT permitted for use in potable water distribution systems inside a building?
- Copper tubing (Type L)
- Cross-linked polyethylene (PEX)
- Lead pipe (Correct answer)
- CPVC
Correct answer: Lead pipe
The IPC expressly prohibits lead pipe in potable water systems due to its well-documented health hazards. Copper Type L, PEX, and CPVC are all listed approved materials for interior potable water distribution.
Question 2: The IPC requires a pressure-reducing valve (PRV) to be installed when the building water pressure exceeds a certain threshold. What is that threshold?
- 60 psi
- 80 psi (Correct answer)
- 100 psi
- 125 psi
Correct answer: 80 psi
IPC Section 604.8 requires a pressure-reducing valve whenever the static water pressure supplied to a building exceeds 80 psi, to protect fixtures and piping from excessive pressure.
Question 3: Under the IPC, what type of device must be installed on the water supply line serving a hose bibb (outdoor hose connection) to protect the potable water supply?
- Pressure-reducing valve
- Atmospheric vacuum breaker (Correct answer)
- Double-check valve assembly
- Air gap fitting
Correct answer: Atmospheric vacuum breaker
The IPC requires an atmospheric vacuum breaker (or equivalent backflow preventer) on hose bibbs because a garden hose submerged in a bucket or chemical solution can back-siphon contaminants into the potable supply. An atmospheric vacuum breaker is the standard protection at this type of connection.
Question 4: According to the IPC, what is the minimum pressure that must be maintained at every fixture in a building's water distribution system during peak demand?
- 8 psi
- 15 psi (Correct answer)
- 20 psi
- 30 psi
Correct answer: 15 psi
IPC Section 604.3 sets 15 psi as the minimum flow pressure required at every plumbing fixture. Pressure below this threshold results in inadequate flow and potential backflow conditions.
Question 5: When sizing a water distribution system, the IPC uses fixture units to estimate demand load. What term describes the method used in the IPC for converting fixture unit counts into pipe size?
- Hunter's Curve method (Correct answer)
- Hazen-Williams formula
- Darcy-Weisbach equation
- Manning's equation
Correct answer: Hunter's Curve method
The IPC's pipe-sizing tables and demand-load conversion charts are based on Hunter's Curve (the Roy B. Hunter method), which correlates fixture unit totals to probable peak flow rates for sizing distribution piping.
Question 6: A plumber installs a water hammer arrestor in a supply line serving a clothes washing machine. According to the IPC, where is the correct location for this device?
- At the water meter
- At the main shutoff valve
- As close as possible to the quick-closing valve or solenoid causing the hammer (Correct answer)
- At the building's pressure-reducing valve
Correct answer: As close as possible to the quick-closing valve or solenoid causing the hammer
IPC Section 604.9 requires water hammer arrestors to be installed as close as practical to the quick-closing valve (such as a washing machine solenoid) that causes the pressure wave. Locating the arrestor at the source of the shock is essential for it to effectively absorb the surge.
IPC - International Plumbing Code Water Supply and Distribution 2
According to the IPC, which of the following pipe materials is NOT permitted for use in potable water distribution systems inside a building?