Our house was built in 1988. We are the original occupants. I have replaced windows, garage door, furnace, AC, roof(s), etc in the 33 years, but we are still on our original water heater (AO SMITH). I am sure we are living on borrowed time (I do connect a hose to the drain valve and open it for a couple minutes twice a year, but that's all the maintenance I've done on it).

Beginning a couple years ago, we have been experiencing a recurring water hammer in our kitchen - on the hot water side. When it starts acting up, the dishwasher groans when we start up a load, then we start getting a water hammer when we shut off the hot water at the kitchen sink. it starts out barely noticeable, then gets progressively worse over a period of several weeks. No water hammer anywhere else in the house, just the kitchen sink/dishwasher hot water.

To (temporarily) remedy the water hammer, I do the whole house drain, then refill. That stops the water hammer for 2-5 months, then it comes back.

Do you think our aging water heater could somehow be contributing to this water hammer? If not, are there any other thought or suggestions you can share with me to take care of this? It's not particularly urgent, just annoying, and getting to be more so.

Thanks for any help.

 

No, I think the water heater and your water hammer are totally separate issues. I think you may have water hammer arrestors somewhere or something that is acting like one since you can make the problem go away by completely draining your house's piping. You could install modern diaphragm type hammer arrestors. They should work for years without needing the draindown.

 

Also check the position of the hot water valve under the sink. Make sure it is fully open. Check that the valves under all sinks and washing machine are full open.

 

Agreed, I doubt it's actually the water heater.
Do you have a pressure tank anywhere? (metal tank attached to the water piping, usually near the water heater). Or do you have a PRV near the meter (probably not an issue as draining down the system resolves it.

 

Thanks everyone for the suggestions. Sorry for the delay responding - I did not receive any notification that anyone had replied to my post.

I will check to make sure the water shutoff valves are wide open at all appliances. I will also look into the diaphragm arrestors.

Zorftd, we do have a pressure tank, as we are on a well. Now and then I need to drain it and re-pressurize it, as the air bladder becomes waterlogged. I last did that about 3 years ago. It would be interesting if there were an interaction between the pressure tank and the water hammer in the kitchen hot faucet.

 

It could very well be the pressure tank. The purpose of the pressure tank is to equalize the pressure as the water heats and cools. It sounds like when your pressure tank gets waterlogged, it stops doing its job and the pressure in your system increases. The high pressure is then likely causing the water hammer.

Recommendation is to replace the pressure tank. This sounds like it should resolve your problems!

 

Is the water heater located directly below the kitchen? That's a fairly common house design (minimal heat loss because the hot water lines are short) but it can create a water hammer problem because the pipe may be only a few feet long from the heater outlet to the kitchen sink.
Actually, first I'd try replacing the valve in the 'tire stem' that you used to pressurize the tank.
You just need a "valve stem puller" which you can get from any bicycle shop, or online

Turn off the valve between the pump and pressure tank to isolate the pressure tank if you have a valve between the tank and the house, close that to. Open the drain to remove the pressure, then remove the valve using the slot at 4-o'clock, clean/chase the threads with the tap at 7-o'clock, and inspect the air valve. Sometimes they wear down or hard water / gunk keeps the seal from closing.
Reverse the process and reassemble.

 

Hal_s: interesting. The reason I can remember the last time I recharged our pressure tank was because while I was trying to recharge it (using a bicycle pump attached to the valve stem), it snapped off. This was the night before I had a very important meeting at work, in February 2018. I was a bit panicked, since that little valve stem breaking rendered the house water-less. I searched the local big box stores (Ace, Lowes, Home Depot), and all of them said I needed a plumber. 8:00 at night, middle of winter - My last stop was Menards, and the guy in plumbing took me to the aisle where they had 2 or 3 types. I love Menards. I replaced the valve, pressurized the tank, and never thought about it again. Perhaps I should simply replace the valve stem again. It was only a couple bucks.