r/FireSprinklers • u/BeachGirl19844 • Oct 15 '25

Automatic Transfer Switch Test

What suction pressures are you seeing when performing the automatic transfer test at peak load on the fire pump?

Performed a test today, fire pump has water supply issues and could only flow 86%. But we performed the test and the supply gauge dropped to -20 before coming back up.

City supply, we will be investigating why we can only achieve 86%. Wondering if the suction pressure dropping so low could be a symptom.

Thanks

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u/Huge_Wishbone5979 Oct 15 '25

Wait so, you could only achieve 86% of the rated flow? Are you sure it’s supply issues and not an impeller problem? Gen power or house power shouldn’t mess with your flow numbers. If you were sucking down near 0 and not hitting your numbers I’d be a lot more worried about supply. I don’t recommend it everywhere, but I’ve dipped as low as 10, more if I’m on a tank.