Just had new Navien 240A tankless hot water heater installed and new PEX 3/4” on main loop hot, cold and recirculator lines. Tapping and clicking throughout house every 15 minutes when hot water heater kicks on to maintain temp in recirc line. We didn’t like waiting up to 2-3 minutes for hot water to reach our master which is a good 70-80 feet from the hot water heater, so I believe it must be on a “comfort” setting for recirc.
I’m assuming the sounds are from expansion and contraction in recirc line. Any suggestions for a fix? Clicking and tapping wakes me up at night and hard to fall back to sleep as frequently as it occurs.

WOW, i want to say that over the years i have probably run miles of pex pipe for both hot water and hydronic heating. i can honestly say i have NEVER had an expansion/contraction noise problem.
my thoughts here are to slow down the flow of the circulation loop. maybe some kind of a simple flow restrictor ?

you have to check with the manufacturer to make sure my suggestion will not cause other problems ?

? clicking/'rattling' swing check valve ?

you can try replacing it with a 'soft seat' type aka rubber seat

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



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i don't know, bern.
he said noise is throughout the house. noise doesn't transmit thru pex tubing like it would thru metal piping.
i'm guessing that since this is a new install that a circulator with an internal flow check would have been used ?
these type are plastic spring loaded and ball shaped. i can't imagine it would make a noise. but then ?

agree ... ? but then ?




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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Wire the re-circ off a timer, so it shuts off over night. Pex does have a very high expansion rate. What's more concerning is the fact that it is rubbing. A "plastic" hose rubbing on something could be a recipe for disaster. Time to put on the "Dick Tracy" hat and get to work. Start checking every place the pex penetrates something. If it's ticking and you put your hand on the pex at that point it will stop.
I've heard a lot of complaints from people that install the type of radiant heat below the floor that uses pex and heat transfer plates. It can be very noisy. I realize you have a different situation, but I make the point to emphasize that pex can be noisy.



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