Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsMedium
Which of the following materials is generally NOT approved for use as a potable water distribution pipe within a building, but IS commonly approved for drainage, waste, and vent (DWV) systems?
- ASchedule 40 PVC (Polyvinyl chloride)
- BCPVC (Chlorinated polyvinyl chloride)
- CPEX (Cross-linked polyethylene)
- DCopper (Type L)
Show answer & explanationAnswer & explanation
Correct answer: A. Schedule 40 PVC (Polyvinyl chloride)
Schedule 40 PVC is widely used for DWV systems due to its cost-effectiveness and chemical resistance, but it is generally not approved for potable water distribution within buildings because it cannot withstand the higher pressures and temperatures required, and some jurisdictions have concerns about leaching. Copper, PEX, and CPVC are all approved for potable water.
Why the other options are wrong
- B. CPVC is specifically designed and approved for hot and cold potable water distribution, with higher temperature ratings than PVC.
- C. PEX is a common and approved material for potable water distribution, especially for hot and cold lines.
- D. Copper (Type L) is widely approved for potable water distribution and sometimes for DWV.
DWV vs. Potable Water Piping Materials
Different piping materials are approved for distinct applications (drainage vs. drinking water) due to varying pressure, temperature, and health requirements.
- DWV pipes handle low pressure, non-potable waste.
- Potable water pipes handle higher pressure, clean water.
- Material properties like temperature rating and leaching are critical.
Memory trick: Clean water, dirty water, different pipes, different charters!