Free Master Plumber Water Supply and Distribution Questions and Answers — Questions and Answers
Question 1: A master plumber is installing a water service for a new single-family residence. The static water pressure from the municipal main is measured at 95 psi. According to the International Plumbing Code (IPC), what is the required action?
- Notify the water purveyor to lower the main pressure.
- Install a pressure-reducing valve (PRV) set to not exceed 80 psi. (Correct answer)
- No action is required as 95 psi is acceptable for residential fixtures.
- Install a booster pump to maintain consistent flow.
Correct answer: Install a pressure-reducing valve (PRV) set to not exceed 80 psi.
IPC Section 604.8 requires that a pressure-reducing valve be installed when the static water pressure in the water supply system exceeds 80 psi. This is to protect fixtures, appliances, and piping from damage caused by excessive pressure.
Question 2: Which of the following devices is specifically designed to be installed in a potable water piping system to absorb the high-pressure shock waves caused by the quick closing of valves?
- Water hammer arrestor (Correct answer)
- Expansion tank
- Pressure relief valve
- Check valve
Correct answer: Water hammer arrestor
A water hammer arrestor is an engineered device that contains a piston and a sealed chamber of air or gas that compresses to cushion the pressure surge, or 'water hammer,' that occurs when water flow is suddenly stopped. While an expansion tank also absorbs pressure, its primary purpose is to handle the gradual pressure increase from thermal expansion.
Question 3: A master plumber must protect the potable water supply for a commercial boiler that uses chemical additives for treatment. Which of the following backflow prevention assemblies provides the highest level of protection and is typically required for this high-hazard application?
- Double Check Valve Assembly (DCVA)
- Atmospheric Vacuum Breaker (AVB)
- Reduced Pressure Zone (RPZ) Assembly (Correct answer)
- Pressure Vacuum Breaker (PVB)
Correct answer: Reduced Pressure Zone (RPZ) Assembly
A Reduced Pressure Zone (RPZ) assembly is required for high-hazard cross-connections where the non-potable substance, if it entered the public water supply, could cause illness or death. Boilers with chemical additives fall into this category. The RPZ provides maximum protection by creating a zone of reduced pressure between two check valves and featuring a relief valve that discharges to the atmosphere if backflow occurs.
Question 4: After completing the installation of a new water service line for a commercial building, what is the generally accepted procedure a master plumber must follow before the system can be put into service, according to most plumbing codes and health standards?
- Flush the system with hot water for a minimum of 30 minutes.
- Purge the system with compressed air to remove debris.
- Conduct a hydrostatic pressure test at 150 psi for 4 hours.
- Fill the system with a chlorine solution, let it stand, flush, and test for residual chlorine. (Correct answer)
Correct answer: Fill the system with a chlorine solution, let it stand, flush, and test for residual chlorine.
New potable water systems must be disinfected to kill bacteria introduced during construction. The standard method, outlined in standards like AWWA C651, involves filling the pipes with a chlorine solution (typically 25-50 ppm), allowing it to stand for a specified period (e.g., 24 hours), then flushing with clean water until the chlorine residual is safe.
Question 5: To prevent excessive noise and erosion-corrosion within a copper potable water distribution system, what is the generally recommended maximum design velocity for cold water?
- 4 feet per second (fps)
- 8 feet per second (fps) (Correct answer)
- 12 feet per second (fps)
- 2 feet per second (fps)
Correct answer: 8 feet per second (fps)
Accepted plumbing engineering practice, as referenced by the Copper Development Association and other industry sources, recommends a maximum velocity of 8 feet per second (fps) for cold water in copper piping. Exceeding this velocity can lead to noise (hydraulic shock) and accelerate the erosion of the pipe's interior surface.
Question 6: Which of the following is a mandatory requirement for the discharge pipe connected to a temperature and pressure (T&P) relief valve on a water heater, according to the International Plumbing Code (IPC)?
- The pipe must be pitched to drain towards the valve to prevent freezing.
- The pipe must terminate unthreaded, no more than 6 inches above the floor or an approved receptor. (Correct answer)
- The pipe can be reduced in size from the valve outlet to the point of discharge.
- The pipe must be threaded at its outlet to allow for a temporary hose connection.
Correct answer: The pipe must terminate unthreaded, no more than 6 inches above the floor or an approved receptor.
IPC Section 504.6 specifies that the T&P discharge pipe must terminate unthreaded to prevent accidental capping or blockage. It must discharge by gravity through an air gap, with the end of the pipe located not more than 6 inches above the floor or an approved indirect waste receptor to prevent scalding from splashing water.
Free Master Plumber Water Supply and Distribution Questions and Answers
A master plumber is installing a water service for a new single-family residence.
The static water pressure from the municipal main is measured at 95 psi.
According to the International Plumbing Code (IPC), what is the required action?