I had my hot water tank replaced a few months ago and have noticed that, occasionally, the pipes make a loud banging when the toilet / washing machine are run. This is not a constant issue.

Initially the bang sounded like it was from the pipes vibrating againgst the joists and a coupe of spots where it touches the air ducts. I clamped / foam insulated these areas, but the banging continues. The bang sounds like it comes from a spot about 10' away from the hot water heater and not near any of the toilets or sinks. I've also drained the system with no success.

The installation company says they will come to investigate but if it's not the hot water heater - they, of course, will charge for the call!

We've lived in the house 9 years without any plumbing issues. Water pressure is fine throughout the house. Any suggestions?

It is usually some device attached to your plumbing system that generates the noise. Sometimes, w/h has nipples that have built-in check valve. That may produce the noise. Also hot water circulating pump. If not, than go to your toilet and Close and Open the water supply valve. It may have loose part in it.

Let us know what it was...

Thanks - I tried shutting off both toilets and drained the system as well. No luck - still have the noise. I had my son turn the tub taps on quickly, while I listened downstairs. I could hear the banging coming from inside the water heater - sometimes single bangs, sometimes multiple. Sounds like it may be the w/h valve you mentioned. I'll call the installer back to take a look.

Thanks for the help.

Would this be a gas or electric water heater? If It's a gas heater I may just have the answer. Regards, Tom

Thanks - it's a gas w/h