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Jeffrey
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Long Island
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Water Hammer: Possible Causes?

This is a problem that is actually fixed, but I'm mainly looking for some education on the matter since I know very little about plumbing.

My wife and I moved into our home in 2008. The washing machine always worked fine. At some point, I want to say like 2010, pretty severe (as far as I'm concerned) water hammer occurred whenever the washing machine stopped calling for water. I could hear it 4 rooms over, and a floor above as the pipes shook. I cringed every time my wife did a load a laundry.

We struggled with the cause for a while, because the problem of water hammer wasn't here originally in 2008. It appeared later on. Based on this knowledge, we began to think of plumbing repairs we had done to the house. While we replaced some 30 year old gate valves to ball valves at major points, the only thing that came to my mind that could be an issue would be the way the valve was inserted by the local appliance store for our new fridge's ice maker...

They used a self piercing valve into a cold water pipe in the basement's drop ceiling, and fed copper through an existing hole in the kitchen floor to the fridge's necessary hookup point. I believe this same pipe heads right to my washer, based on proximity. The washer is the only unit in the house that was producing the water hammer. I have since put hammer arresters on the washer which has fixed the problem, but am I correct to assume that a self-piercing valve could be the cause for water hammer to occur?

The silence I have now is remarkable.
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Lurch77
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Oconto, WI
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1 recommendation

What you experienced is the type of water hammer known as hydraulic shock. The cause was the water valve in the washer slamming shut. This causes the energy of the water to be instantly dead headed, and it dissipates it's energy in all other directions. This is quite common, especially on washing machines. But it can happen if you slap a faucet off very fast, or even some toilet valves as well. Why it was not happening until a certain point in time is beyond me. Though you may have a failing pressure reducing valve. You may consider check your home's water pressure. I don't know how a piercing valve would cause the issue.

Bob4
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join:2012-07-22
New Jersey

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reply to Jeffrey
A bit of a long-shot, but... If you have an expansion tank on your water heater, make sure it hasn't failed and filled with water.


bbrcat
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said by Bob4:

A bit of a long-shot, but... If you have an expansion tank on your water heater, make sure it hasn't failed and filled with water.

Not a longshot by any means. Mine had "failed" and had to be replaced after just 12 years or so.
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sempergoofy
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Smyrna, GA
How does one determine if the expansion tank has failed? Tap it and listen? Or is there another a procedure?
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Bob4
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said by sempergoofy:

How does one determine if the expansion tank has failed? Tap it and listen? Or is there another a procedure?

Tapping it, if you have a good ear. Another way is to turn off the main water shut off, then open a faucet for a sink. If the water flows under pressure for a while (30 seconds?), the expansion tank is OK. If the water flows under pressure for just a few seconds, the expansion tank is no good.

Perhaps someone else has another way to test it.


Subaru
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Greenwich, CT
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reply to Bob4
said by Bob4:

A bit of a long-shot, but... If you have an expansion tank on your water heater, make sure it hasn't failed and filled with water.

Hmm I never knew water heaters used expansion tanks.. I know the furnace here uses it but I don't see one for the water heater.


Coma
Thanks Steve
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NirvanaLand

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In lieu of an expansion tank, I have seen a short length of pipe, capped and plumbed in vertical to the water supply line.

Old plumbers trick.

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rfhar
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said by Coma:


In lieu of an expansion tank, I have seen a short length of pipe, capped and plumbed in vertical to the water supply line.

Old plumbers trick.

This is the way most houses have been piped for decades locally. And the air can get out of these risers. the way to fix it is to drain all the water from the pipes and than turn the water back on again.
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Lurch77
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Oconto, WI
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Agreed, the water will absorb the air and eventually fill the riser. Same thing with the old style open expansion tanks. You have to periodically drain them as they would become water logged over time.

Piping in a riser, old school style, is an interesting idea. A guy could put in a couple valves and tee to empty it without pulling down the entire house. But if you are going to go that far, just stick an expansion tank in the system.


Jeffrey
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Thanks for the replies everyone. I never thought of the expansion tank. We had an issue with the hot water heater in Jan of 2010. The pressure release valve got stuck open, and hot water poured out in the basement. Luckily, we were home and I can't imagine it was going on for more than an hour, so it wasn't a huge deal, but the valve and the expansion tank were replaced at that time.

I'll check out the little test procedure anyway. For now, the hammer arresters have done the trick.

Thanks for the info/explanations.
--
He used to say that soul shine, is better than sunshine, better than moonshine, damn sure better than rain.

Debunking the 2012 hysteria. | Always looking for a new job | Begging the Wilpons to sell the Mets.


jrs8084
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Statesville, NC
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reply to Subaru
said by Subaru:

said by Bob4:

A bit of a long-shot, but... If you have an expansion tank on your water heater, make sure it hasn't failed and filled with water.

Hmm I never knew water heaters used expansion tanks.. I know the furnace here uses it but I don't see one for the water heater.

They didn't in the past, but when city water services started installing check valves (to prevent back flow-say I pipe in a well or somehow taint my water lines), these became necessary.) Fill a cold water heater, and the water expands. In the past, it just pushed back into the city water supply. With the check valves, you PSI goes through the roof. Hence the need for an expansion tank.

robbin
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Leander, TX
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reply to Bob4
said by Bob4:

said by sempergoofy:

How does one determine if the expansion tank has failed? Tap it and listen? Or is there another a procedure?

Tapping it, if you have a good ear. Another way is to turn off the main water shut off, then open a faucet for a sink. If the water flows under pressure for a while (30 seconds?), the expansion tank is OK. If the water flows under pressure for just a few seconds, the expansion tank is no good.

Perhaps someone else has another way to test it.

The expansion tank should have an air valve on it like a tire does. Turn off the water and open a couple of faucets. Then use a pressure gauge to check the pressure. It should be set a few psi lower than the water pressure of the house. Best to use a bicycle pump if you need to add air to it as it is very easy to add too much when using a compressor.


Subaru
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Greenwich, CT
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reply to Coma
said by Coma:


In lieu of an expansion tank, I have seen a short length of pipe, capped and plumbed in vertical to the water supply line.

Old plumbers trick.

I will have to check.. the tank is not old old... maybe 10 years at this point.. BUT the pressure release valve is on top of the tank and has no pipe to move it away and down from the tank, it's just the valve it's self and it's somewhat leaking a bit.
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