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 water hammer in hot water heater
Author: Anonymous User

Hey guys, I finally got the expansion tank put on my hot water heater. So far so good. Knock on wood, but the relief valve has quit popping off. I also put a water hammer arrester on the hot line just above the water heater. Anyway everthing has seem to be working ok. The hammer was still there when I turned the water back on, but it was not bad at all. I have noticed that over the last two weeks that the hammer has come back over time. I believe that the hammer is inside the water heater.

The incoming pressure is 44psi after the prv. A backflow is also present.

Now a bit of history. The water heater is electric and 52 gallon. Its 11 years old and I was on a well where I used to get a ton of sediment. This past summer I switch over to county water. When the water heater used to turn on, you could hear it popping louding from the upstairs. Sounded like it was going to blow. I flushed it several times this summer and I have drained it down some when re-doing the cold and hot lines over the past month. It heats up without the loud noises since I flushed it. You can still here some popping inside but you have to have your ear to it.

Not sure where to go from here. The hammer occurs at the water heater on both the cold and hot. If I keep turning the water on and off the noise get louder. Is the noise going to hurt anything? Thanks, Russ

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 Re: water hammer in hot water heater
Author: packy (MA)

water heaters do not cause water hammer.
if the nipples on top of the heater have plastic ball checks in them, they could be the cause.
other causes could be excess pressure or excess velocity(too small piping) or loose piping or loose washers in a valve.

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 Re: water hammer in hot water heater
Author: Anonymous User

I get alot of complaints of those ball checks and even have removed them from the dip tubs in the older water heaters.

After explaining what they are for to the home owner I ask if they want me to pipe in a heat trap, most people say no thats o.k.

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 Re: water hammer in hot water heater
Author: hj (AZ)

Are you hearing the popping noise or a water hammer bang? What do you turn on and off to make it happen? water hammer arrestors at the water heater to not prevent water hammer. Water hammer is caused by faucets or valves shutting off too quickly while water is flowing through them and the arrestor has to be at the valve to stop the hammer. Your description implies that you are hearing the "normal" popping when water is heated in an old tank that has calcium encrustation inside it. Either on the flue of a gas heater or the elements of an electric one.

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 Re: water hammer in hot water heater
Author: Anonymous User

hj, Its a bang noise at the heater any time water is turned on anywhere in the house.

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 Re: water hammer in hot water heater
Author: packy (MA)

the nipples on top of the heater have little plastic balls in them. remove the plastic balls. they were a bad idea in the first place.

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 Re: water hammer in hot water heater
Author: hj (AZ)

True water hammer occurs when a faucet or valve closes. There are several things that could cause a bang when the faucet is opened, starting with a long, undersized water supply pipe.

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 Re: water hammer in hot water heater
Author: Anonymous User

The house has new copper 3/4inch. I used to have 1/2 inch copper and I went to 3/4. I will try to remove the plastic inside the nipples.

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 Re: water hammer in hot water heater
Author: jjbex (IL)

Save yourself a headache. Remove the factory nipples and use brass. I would get rid of the dielectric unions if any and use flexis or brass/copper unions.


Peace out,

Kordts

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 Re: water hammer in hot water heater
Author: lordofthering (NJ)

@packy,
Which nipple are you referring to ? Air Vent ?. I have the same issue from my indirect fired water heater and it is happening when cold water gets into the tank. I think it is due to high pressure in cold water.

How do I remove water ball from Air Vent ?.

Thanks in Advance.

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