Indirect water heater absorbed water hammer?

sunlight33

Recently I had the chance to flush my indirect tank and I noticed banging sound from the water pipe every time I open or close cold water faucet on either floor of my house, it's a water hammer that I have not experienced in this house before. After I finished cleaning the tank and put it back to service I did not notice any of such sound again, granted this was my first time draining the tank since I bought my house a couple of years ago. Could it be the indirect tank somehow alleviated the water hammer?

sunlight33

Yes, before I had the valve closed on the cold water inlet of the tank when I noticed the sound. Normally this valve is open so I thought perhaps the pressure that caused the hammer propagated into the tank and dissipated?
I tried opening just the cold and there was no hammer sound.

Larry Weingarten

Hi @sunlight33 , What is the water pressure with nothing flowing? I've found that higher pressures make water hammer worse and lowering pressure can eliminate it.

Yours, Larry

Jamie Hall

Is there an expansion tank on the hot water side? That will absorb the hammer very nicely.

sunlight33

Water pressure is 50 psi with nothing flowing, it's city water.
There is no expansion tank on the hot water side. Speaking of which, is it fine not to have it?
The two faucets I opened one had separate handles, the other had one handle with a mixing chamber.

mattmia2

Perhaps the tendency of the dissolved gas to come out of water when it is heated is keeping the air chambers on the hot side filled but they are not staying filled on the cold side.

The water in my house bounces back and forth multiple times between the hot and cold side when something shuts off abruptly. My old water heater had mechanical heat traps that would click every time the flow stopped or changed direction. I still expect to hear the multiple clicks when the toilet fill valve closes even though i replaced that water heater 2 years ago.

sunlight33

Do I need to add a hammer arrestor? I can add a tee in the cold water line.

sunlight33

I am going to install an expansion tank at the cold inlet of the indirect. If I have 50 psi water, do I charge the tank to exactly 50 psi or slightly under say 45psi ?

Larry Weingarten

Hi @sunlight33 , I think tanks come precharged to forty psi because of DOT rules, so you'll want to pump it up to match your pressure.

Yours, Larry

ps, The closer you put the tank to the point/s of use, the better it will work as a water hammer arrestor.

sunlight33

I've got almost no space for adding a tank because the cold inlet on my indirect tank is at the very bottom, and the tank itself is about a foot from the water main. The piping goes like this: Water supply -> PRV --> meter --> water filter --> tee, from the tee it splits to the indirect and sillcocks. My question is should the expansion tank be installed between the indirect and the tee or can it be installed anywhere upstream between the tee and the water filter?

sunlight33

I will get an Amtrol tank with the antimicrobial liner and the Flexconsole to assist with installation (they make one for potable water).
As for water hammer I will try to locate it again. It was hard for me the first time because the room was kinda echoey, gonna ask my wife for help this time.