Why is my new Recirculator So Noisy?

[Movieball]

Hi, I need some advice about noise from a new water recirculator. We are almost complete with our new home addition, and installed a tankless water heater and a Gundfos water recirculator. We have a one story house and the pipes from the recirculator run under the house in the crawlspace. The pipes seem to make a constant noise, like the hum of a refrigerator, even though the actual Grundfos recirculator is thirty feet away and on the outside of the house. My question is, is the humming noise normal? Or is this an installation issue? Our plumber said he insulated all the recirculation pipes but this has not fixed the problem at all. It almost sounds like it’s echoing though the old pipes in the old part of our house. It is definitely the recirculator because when I torn it off the noise goes away. Should I live with it? Hire a new plumber to fix it? Any ideas about possible cause? Thoughts? Thank you!

 

[Diehard]

Are all the valves on the recirc system completely open?

Have you tried putting your hand on the circulator to feel if perhaps that was the source of the sound?

Is circulator securely mounted and/or mounted on vibration isolators?

Any valve or device in the piping system that may feel like the source. Granted, being a very minute sound, the offending culprit may not be easily detected by feel.

Is any part of the piping touching the house structure directly?

Was all air completely purged from the system? For example, are there any high spots where it may not have been cleared from?

 

[frodo]

You are experiencing vibration from the pump.
You need to isolate the pump.
There are 2 ways to isolate a pump from vibration
one is 1/2'' thick rubber between the pump and what ever it is mounted on
https://www.grainger.com/category/m...-4107&ef_id=XJIsswAAAHSPEg4G:20191004005301:s
The other
is to isolate the pump from the piping, using a flex connector
buy 2 braided ss flex connectors with male or female ends
install on the inlet and outlet of the pump

 

[Diehard]

If you suspect the pump, I would suggest you remove and inspect it carefully for any foreign material.

If you decide to add pipe line isolators(doubt the pump would have a pad) and still get the sound, ask your plumber if he/she purged all the air out of the system.

 

[breplum]

Grundfos pumps For domestic water piping run so quietly that you cannot even tell that they are running. So, you have something problematic with the installation that the original installer should address at his out-of-pocket cost.
Most major brands, Navien, Rinnai and Noritz Condensing models have the pumps built right into them. Sorry for you