Part 2 — Answer key

Compare your answers after you have finished Part 1.

1. In a typical home, the main water shutoff valve stops the flow of water to all fixtures in the house.
   True
2. What is the primary purpose of the P-trap installed under most sinks?
   Prevent sewer gases from entering the home
3. Which pipe material is most commonly used in new residential plumbing for water supply lines because it is flexible and relatively resistant to freezing damage?
   PEX
4. If a toilet occasionally runs for a few seconds and then stops by itself, that usually means the fill valve is adjusted perfectly and no maintenance is needed.
   False
5. A homeowner is trying to loosen the hard-to-reach mounting nuts that hold a faucet to a sink from underneath the countertop. Which tool is specifically designed for this task?
   Basin wrench
6. On plumbing diagrams and many pipe markings, what color is most commonly used to indicate hot water lines?
   Red
7. A bathroom sink drains very slowly, and using a plunger only helps a little. The trap is accessible under the cabinet. What is usually the most effective next DIY step before calling a plumber?
   Remove and clean the P-trap under the sink
8. When soldering a copper water line, you should heat the fitting and pipe joint, not the solder itself, so that the solder is drawn into the joint by capillary action.
   True
9. When your washing machine drains, water backs up out of a nearby floor drain in the basement, then slowly recedes. Other fixtures on that branch are also slow to drain. What is the most likely cause?
   A partial clog in the main drain line near the laundry
10. While showering, you notice that the water suddenly becomes very hot whenever someone flushes a toilet elsewhere in the house. What upgrade will most directly help prevent these sudden temperature changes?
    Install a pressure-balancing or thermostatic shower valve
11. Most modern plumbing codes require a dedicated shutoff valve on the supply line to each toilet so it can be isolated for service without shutting off water to the whole house.
    True
12. You are dealing with a routine clog in a bathroom sink and want to try safe DIY methods before calling a plumber. Which of the following are appropriate approaches? Select all that apply.
    Feed a small hand-operated drain snake into the drain; Use a plunger while sealing the overflow opening with a wet cloth; Remove and clean the sink stopper assembly
13. It is generally safe to hang heavy storage items, such as bicycles, from exposed copper water pipes in a basement as long as the pipes are not carrying hot water at the time.
    False
14. A homeowner is adding an in-ground lawn irrigation system that connects to the home’s potable water supply. What device is typically required by plumbing codes to prevent contaminated water from flowing back into the drinking water system?
    Backflow preventer
15. A plumber is installing a new water heater. How should the discharge pipe from the temperature-and-pressure relief valve be routed according to good practice and typical codes?
    Run downward to a visible, safe drain termination point
16. Several fixtures in the lowest level of a house gurgle and drain slowly, and wastewater sometimes backs up from a basement floor drain when the washing machine discharges. What is the most likely underlying problem?
    A partial blockage in the main sewer line
17. You need to repair a standard single-handle faucet that is dripping from the spout by replacing the internal cartridge. Arrange these general steps in the correct order.
    Correct order: Shut off the water supply and relieve pressure at the faucet → Remove the handle and any decorative caps or trim pieces → Extract the old cartridge from the faucet body → Install the new cartridge and reassemble the handle components → Turn the water back on and test for leaks and proper operation
18. A busy restaurant kitchen has recurring clogs and slow drainage in the main line serving its dishwashing and cooking areas, even after snaking the line several times. Which solution most directly addresses the root cause according to good plumbing practice?
    Install and properly maintain a grease interceptor on the kitchen waste line