Hammer Arrestor Placement for Tankless Recirc Pump?

Users who are viewing this thread


New Member
Reaction score
I'm fairly competent, but also feeling rather stumped. Hoping for some direction and clarity here.

: Using a tankless heater with internal recirculation pump. The house (multi-baths across multi-floors) has a dedicated recirculation line, and the recirc pump runs at at scheduled times throughout the day (to align with family showers, doing dishes, etc.).

Issue: We've noticed when the recirc pump finishes its run cycle and shuts off, we experience water hammer. Can't access the pipes in the walls directly to brace them better against the studs without tearing down the drywall. Would like to try other options like a water hammer arrestor first.

* Please note we're planning to also add stub hammer arresters at the various fixtures as a good general practice, but that won't necessarily help us address the hammer caused by the recirc pump inside the water heater.

QUESTION: Knowing that arresters work best when placed nearest to the offending fixture, it's unclear to me where is best to place the water hammer arrestor in our setup (basic diagram [not to scale] attached).

I know I'm overthinking this and keep second guessing myself, so welcome input from others on best path forward (or advise if perhaps another expansion tank on the HOT water line would be better here... OR maybe even add both an arrestor and an additional ET??).

Thanks in advance for any direction.

Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks