During the flow test, when should the main drain valve be opened?

During the flow test, when should the main drain valve be opened?

• A. The beginning of the flow test
• B. Midpoint of the flow test
• C. End of the flow test
• D. Never opened

Answer: (A)

Opening the main drain valve at the very start of the flow test is essential to vent the system and provide a clear discharge path. Doing this ensures air is expelled from the piping and that water can flow freely into the drain, giving an accurate measurement of the available flow without pressure buildup behind a closed drain. If you wait to open it, air pockets can distort readings and the test won’t reflect the true supply capability. Opening at the beginning gives a correct baseline and a consistent flow for the test period.

Opening the main drain valve at the very start of the flow test is essential to vent the system and provide a clear discharge path. Doing this ensures air is expelled from the piping and that water can flow freely into the drain, giving an accurate measurement of the available flow without pressure buildup behind a closed drain. If you wait to open it, air pockets can distort readings and the test won’t reflect the true supply capability. Opening at the beginning gives a correct baseline and a consistent flow for the test period.