What makes the "whump!" sound in my heat pump when the pump shuts off, like kicking a large.plastic barrel?

Question

It didn't start doing it until after the serviceman replaced some parts. Otherwise it seems to run fine. Its about 8-10 years old.

Answer 1

Favourite answer

That is the sound of the ducting relaxing and popping back to its original shape once the pressure of the fan has ended.

This can be remedied by bracing the ducting. It may take a pro to figure out WHERE to brace it.

Answer 2

There is a check valve on the discharge side. It checks or stops water going back into the sump. It slams into place when after the pump stops pumping. Sometimes..the valve is turned seasonally. But, turn the valve and you will stop that noise. They also make a "quiet" valve.. good luck

Answer 3

Whump! There it is! The serviceman probably didn't tighten something.