Residential hydronic heating system water hammer

Zoso

I hear a lot of water hammer with my hot water heating system at the house. It has three zones with Honeywell valve and one zone for the bathrooms with no valve. I don't hear it so much in the boiler room as I hear it especially in the back of the house farthest away from the boiler room. I haven't been able to pinpoint exactly the cause but I'm pretty sure it's when a zone valve closes. I would have thought having one zone that's always wide open would mitigate this problem but it still exist. I haven't looked at bracing the piping better or anything in the far reaches of the house. I just wanted to try to understand if there's something that could or should be done at the boiler.

I'm pumping into the expansion tank which I know is not ideal but this system was installed in 1978. I've been in the house for 16 years and have noticed the hammer but it seems like it's worse lately. I did just have one of the zone valves replaced and I went with a cheap Honeywell like the one that was there. Perhaps the pump is oversized but don't really know what kind of specific flow I'm getting. Here are some snapshots that might be helpful. Pump is on the return. Expansion tank is on the discharge of the pump and then the pipe goes into the boiler out of the boiler and to the manifold with the zone valves.

Any suggestions would be appreciated. Particularly those that won't require me to shut down as winter is pretty much here. Thank you

hot_rod

Odd that it just started after all these years?

The flow direction is correct on the new valve?

Under the cover of the zone valve you see two return springs. Some folks have been able to solve a hammer by unhooking one spring. Basically you are trying to slow the close off.

Water hammer starts at the valve but transmits throughout the piping in the zone, so you hear it everywhere. Sometimes called elastic shock as the pressure zone builds and releases.

The circ is a good match for your system.

Zoso

No it's been there for years but it just seems like it's more frequently now. Or maybe I'm just noticing it more. Should I try to Throttle Down any of the valves a little bit to reduce flow?

hot_rod

Throttling flow would reduce heat output, and I doubt it will change flow velocity.

There are circulators now that vary their speed as zone valves open and close that can make a difference, called ECM delta P. As the valves close off, they slow down, never over pumping the system.
Cruise control built into the circulator basically.