Hot water flow stuttering at sinks

Does anyone know what causes the hot water to pulsate and peter out to nothing during a functional flow test of multiple fixtures running in one bathroom at the same time?

I never saw that before. Do you have information on the plumbing system? Is it on a well? Is there a recirculating pump?

A well water pump that pulsates is usually an indicator that there’s not enough pressure in a water tank. … If either of these is worn out or not working, this can cause a pulsating water flow due to water surging in the pipes…JMHO


The home is on a public water supply, not a well.
It does have high water pressure at 92 PSI.
Interior water supply pipes are copper and PEX.
The main water supply line is polyethylene Numex Plastics.

I did not see a recirculating pump anywhere.

You should share the link from where you obtained the information. :grinning:


These are the shutoff valves for both of the sinks combined.

Sorry, Larry. I should have given more information in my first post on this thread about it being on a public water supply.

Remove those Flood safe auto-connectors.
Had one of those before on a washing machine to replace a water hose connector, and did the very same thing when there is to much demand for water.
Try opening one fixture at a time.
The one I had installed was a little different than what shown in the link, but did the same thing. I was able to modify it so not to loose the cost of the connector.


Is it vented properly?

What does a vent have to do with ‘supply’?


Does the home have a ‘Closed Plumbing System’ with an Expansion Tank?

Any chance it has a tankless water heater? I see those units “pulse” or flutter occasionally, but never that bad.

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An expansion tank was not present anywhere in the house at the time of the inspection.

The tanked electric water heater at the home was an 11-year-old Reliance.

When you say ‘Closed Plumbing System,’ are you referring to a home with a backflow preventer/check valve that’s installed on the main supply line? I did not see a backflow preventer, but there very well could have been one out in the yard somewhere.

@mcyr Thank you, Marcel. After reading that Watts FloodSafe manual, I think that the water pressure for this home should first be lowered down from the 92 PSI where it’s at. Then, the functional flow of water at these pulsating fixtures should be reevaluated.

Those FloodSafe connectors are interesting. I’d never heard of them before. I’m guessing that this won’t be the last time that I see pulsating water like that at the sinks.

Thanks for the link, Junior. I had but a few minutes then. :man_shrugging:t2:

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Yes. If so, it is typical to have an expansion tank installed, but that doesn’t always happen, and would account for some issues you mentioned, such as the high pressure, and other issues.

Thank you, Jeffrey.
The high water pressure problem was one of my top five concerns that I mentioned to my clients as needing repair.
I called out the missing expansion tank, as well.

Marcel nailed it. It’s those hoses that are being used. Pressure is too high for them. Put one on a toilet once and it would do the same thing. Took an hour to fill the tank and made the pipes hammer.

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