water heater buzzing when running water

Thanks to all who replied. I will try to get to the check valve. My water heater is in the back closet which is very full. Thanks again.

Definitely the check valve. It either has debris in it or has come apart inetrnally. If it is easily accessible it would be easy to replace. If hard to get to then may not be worth the effort. Mine has been doing it for 3 years now. It is not easy to get to.

Open up the outside pop off relief valve and let water run. See if you get the buzzing sound. IF NOT, then the check valve on the water heater is the problem. The Check valve is NOT supplied by the Water Heater maker, but by the RV maker and there may be 2 check valves. On the Input and one on the Output. Doug

I agree it's the check valve. I ignored mine and it went away after a while.

That happened on my suburban water heater when it was brand new and then stopped (one time). I am chalking it up to foreign debris in the check valve and must have cleared itself. My guess is your check valve sticking.

Check valves buzz at low flow, and I agree it is the check valve.

What kind of bypass do you have
Single valve, requires a check valve on the outlet. OR you can replace the check valve with a quarter turn

2 and 3 valve systems do NOT need check valves

Some companies put check valves on both the outlet and the inlet, why, I will never understand, but they do it.

Don't want to alarm, but this is something you need to solve. More than once in my 35 years repairing home appliances, I have heard what I would describe as a buzz, that turned out to be a short. It happens when you run the water because that's when the elements kick in. The WH is propane or 120 VAC, so it's not a huge electrical issue. The relief valve is definitely a possibility, also. Just try to get it solved rather than just give up. No one wants an emergence if we can solve before then. hth

It might be the check valve on the hot outlet is a bit gummed up with mineral build up. If you can readily access the back of the tank, hold your hand on the check valve (looks like a coupling with an arrow on it) while someone runs some hot water. The check valve can be removed and soaked in vinegar or CRL to clean it up, or replaced.