Two new water heaters - rattle sound

I'm having a real hard time with this one: I recently replaced both water heaters in my house at the same time (both are Whirlpool 40 gal. natural gas).

Right away we noticed that whenever a hot water valve is turned off (sink, shower or washing machine), there is a short but noticable rattle coming from inside the wall (directly behind the water heater).

I tried draining the the water from all the house pipes to ensure the air chambers weren't water logged but to no avail.

Any ideas what could cause this?

Sounds to me like :
you have a piece of solder that got flushed into the pipe at the time of installation . VERY HARD to get out without cutting pipe

or

A hanger/strap came loose and when the valves/faucets get shut off the pressure (up or down) is shaking the pipe.

You might be cutting the wall either way.

Sorry,

Cal

Sounds like a loose pipe to me...
Only way to fix it is to re-anchor it...

Semi off the main subject but with 2 water heaters do you have a expansion tank. With the mention of air chambers it looks like you have had a problem with water nock witch can be made worse with high pressures because of water expansion.

I don’t think this will help to much but it could solve a your current problem. It will solve problems down the line that you don’t have yet.

rattling soundsin whirlpool heaters

depending on where the rattling
sound is comming from

you might want to check out the tops
of the heaters to see if their are check
balls inserted into the nipples.... they will rattle

on another note
those are the worst water heaters on the market
so you will probably be changeing them out in a year
or two anyway