CSLB C-36 Plumbing ContractorPlanning and EstimatingMedium
A plumbing contractor is tasked with installing a new water main connection for a commercial building. The local water authority requires a specific type of valve for the main shut-off on the customer side of the meter. Which of the following valve types is typically specified for this application due to its full-bore flow and quick shut-off capabilities?
- AGlobe valve
- BCheck valve
- CGate valve
- DPressure Reducing Valve (PRV)
Show answer & explanationAnswer & explanation
Correct answer: C. Gate valve
A gate valve is commonly used as a main shut-off valve because it provides a full-bore opening when fully open, resulting in minimal pressure drop and unimpeded flow. Its design allows for quick and complete shut-off of the water supply, which is crucial for emergency situations or maintenance.
Why the other options are wrong
- A. Globe valves are designed for throttling flow, causing significant pressure drop, and are not suitable for main shut-off.
- B. Check valves prevent backflow and are not used for manual shut-off.
- D. PRVs reduce pressure and are not designed as primary shut-off valves, though they may be installed after the main shut-off.
Gate Valve Function
A gate valve is a full-port, multi-turn valve primarily used for complete shut-off or full-open service, offering minimal flow restriction.
- Ideal for main shut-off applications (water, gas).
- Not designed for throttling or flow regulation.
- Provides a tight seal when fully closed.
Memory trick: For main shut-off, you need a 'gate' that opens wide and closes tight.