Persistent Banging Noise After New Recirculating Pump Installation – Need Help Troubleshooting

[quito_mont]

Hi everyone,

I'm seeking advice on a persistent banging noise after installing a new Grundfos Comfort PM recirculating pump. The noise typically occurs when an appliance shuts off its valve or after a toilet finishes filling. The sound—similar to a water hammer effect—occurs with both hot and cold water shut-offs and seems to come from the area near the check valve, close to the water heater.

Here's what I've done so far:

1. Installed Water Hammer Arrestors: Added arrestors at the toilet and appliance inlets, which helped somewhat, but the banging noise continues.
2. Location of Sound: The noise appears to come from around the check valve or possibly near the pump itself.
3. Occurrence: The sound most frequently occurs during valve shutting but also happens sporadically even when no water is being used.

Any insights on what could be causing this persistent noise? Could it be related to the check valve, the expansion tank, or something else in the system? Any tips on additional troubleshooting steps would be greatly appreciated!

Thanks in advance!

 

[Fitter30]

Complete model number?

 

[Sponsor]

 

[quito_mont]

Complete model number?

Grundfos COMFORT 10-16 TA BU/LC ​

Model #: 98420224

Here’s link to the pump: https://product-selection.grundfos....224?pumpsystemid=2505055165&tab=documentation

 

[John Gayewski]

What's the static pressure in the house?

 

[quito_mont]

What's the static pressure in the house?

60psi

 

[John Gayewski]

I don't think I ever took a picture of this one completely done, but when adding a recirc system we install them like this. It asks less of the check valve.

 

[quito_mont]

Thanks John. I’d have preferred attaching the return to the drain valve. However the space is tight with laundry next to it. Are there components that can be added around the check valve to alleviate the issue?

 

[John Gayewski]

Thanks John. I’d have preferred attaching the return to the drain valve. However the space is tight with laundry next to it. Are there components that can be added around the check valve to alleviate the issue?

What kind of check valve is it?

 

[quito_mont]

What kind of check valve is it?

This one: https://www.homedepot.com/p/Everbil...zheBF5D_U6fS-ojtlt4aAlc_EALw_wcB&gclsrc=aw.ds

 

[John Gayewski]

You could try a spring check. Without being there to assess the situation I can't say if that for sure will work. Is your expansion tank still good? If so it should be absorbing quite a bit of shock.

 

[quito_mont]

I will check on the pressure and see if it is set to 60 psi. Are there ways to check the expansion tank pressure other than drain the entire system?

 

[John Gayewski]

I will check on the pressure and see if it is set to 60 psi. Are there ways to check the expansion tank pressure other than drain the entire system?

Give the schrader valve a quick push and see if any water comes out. Most people install expansion tanks wrong. The schrader valve should be pointing down so you can give it a quick check and it's obvious if there's a problem as the water collects at the bottom. With it upside down a false air pocket can form in the upper portion of the tank that makes it seem OK when it's not. It's also better to valve them off so they can be checked and changed.

You can tap the air side with something metal and it should sound mostly empty.

 

[Reach4]

I will check on the pressure and see if it is set to 60 psi. Are there ways to check the expansion tank pressure other than drain the entire system?

Yes. Just reduce the water pressure to zero by cutting off the incoming water, and opening a faucet to release the water pressure.

 

[GReynolds929]

The swing check should be mounted horizontal. We have had issues before where the swing check at the cold line bangs like you're noticing, the solution was to install a spring check.

 

[quito_mont]

Thanks for everyone’s feedback. Is there a particular brand or model of 3/4 spring valve that is quiet and doesn’t vibrate as much?

I gather feeding the return to hot water tank’s drain valve would make things better. Does anyone see any change to the overall arrangement, or if there are more components that can be added to alleviate random sound/bangs? They are not frequent though I can now hear it from time to time.