Noise when turn on cold water

[rigmaroll]

Recently started noticing a brief sound that occurs (not every time) when turn on cold water when on city water - especially, it seems, at kitchen sink or toilet bowl fill/flush. I describe it as a muffled tap or clunk. Not loud, but quite distinct. Hard to ID where it's coming from, but not from near the fixture in use nor the Nautilus panel. Hope it's trivial but would like to know & if it signals a problem I should be concerned about.

[StephenO]

I'm assuming it's not the water pump, especially because you said it's a tap/clunk noise, and not a motor rumbling style noise. Have you recently drained the water system, and it's just air working it's way through the plumbing? If you can, maybe take a video of the sound, post it on YouTube, and then put the URL on here? It may help others identify the noise for you.

[rigmaroll]

Definitely not the pump as we are on city water. Did drain the system a couple of weeks ago but it happened before then & still does. Toilet was just flushed while I was in living/kitchen area & it was quite pronounced & seemed to be louder here than in the bathroom. I'll try & get a recording to share.

[rigmaroll]

P.S. This recent occurrence was also more than just one sound, more like two (an initial sound and half a second later a follow-up/'echo'

[JBill9694]

Are you using a pressure regulator and If yes, what is it set at? Just to be clear, the noise occurs when you open a valve, instead of closing it? Have you noticed if the noise occurs when a valve is opened quickly as opposed to cracking a valve open, waiting a second, and then opening to valve completely?

[TedS]

The city water inlet check valve could be causing the sound.

[rigmaroll]

I use a basic (Camco?) pressure reducer between city water supply & hose, rated to put out max 40-50psi (& from the way the water flows from the hose before I connect to Nautilus I'd say it's doing its job)
Noise only occurs on opening e.g. when push toilet pedal down to flush. Doesn't have to be opened fully to get the noise. I think a gradual opening does not result in the noise but will check. I know finding source of a mystery noise can be difficult but am confident it does not come from the Nautilus area.

[TedS]

That check valve is easy enough to disable. Turn off the hydrant. Open an inside faucet to relieve system pressure. Disconnect the hose from Nautilus inlet. Remove the inlet screen and reinstall it inverted to hold the check valve open. Reconnect the hose. Turn on the hydrant. See if the sound is or is not still there when you open a cold faucet.