# Water hammer



## arkyplumber (Jan 10, 2009)

Were do most of you guys put shock arestors on the water system to prevent this from happing? I have found that sometimes adjusting the regulator will take out the knocking, but not always. Thanks


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## Ron (Jun 12, 2008)

Here arestors are to be placed at the fixture it serves.


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## WestCoastPlumber (Jun 17, 2008)

I get them as close to the fixture as possible.


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## ILPlumber (Jun 17, 2008)

Same as above usually. On a battery of multiple fixtures we will put a few larger ones off the top of the main in the wall.


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## arkyplumber (Jan 10, 2009)

I have a call were 2 water heaters are tied into series. The hammering is coming from the first heater in line. It comes about every 4 to 5 mins. and last only 1min long. I was going to try to put one on the hot and one on the cold. Do you think this will solve the problem? Thanks


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## Ron (Jun 12, 2008)

What kind of building are you dealing with? What is the pressure at now? Every 4 to 5 min, what valve or faucet is being used at the time? Hammer takes place cause of a fast closing valve somewhere on the system, find the source if you can.


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## arkyplumber (Jan 10, 2009)

This is in a house, and does not matter what faucet is on. It also happens when the faucet is left on, and not when turning off. The psi is 55 pounds at the regulator. It does seem to becoming from the cold side going in the first heater.


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## Ron (Jun 12, 2008)

How loud is it? Is is a knock or more like a tap sounds, reason I ask, could the noise be caused by expansion and contraction of the hot water line secured to tight to a stud somewhere?


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## arkyplumber (Jan 10, 2009)

I would say more of a knock. I did try and put insulation between the joist and pipe, and did not help. Seems to becoming from the heater. I will say these heaters have flex supplies that are curved back and forth before they tie in the copper pipes. I told the homeowner that I would for sure take them off and hard pipe to the heaters, as they already have been leaking. So I fiqured either the arestors which is what I am going to try, or for a second thought maybe expansion tank. Kinda puzzled, but fiqure one of the two has to work. Thanks for the help


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## Ron (Jun 12, 2008)

Worth a try.


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## Tankless (Jun 12, 2008)

WestCoastPlumber said:


> I get them as close to the fixture as possible.


ditto


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## Tankless (Jun 12, 2008)

arkyplumber said:


> I would say more of a knock. I did try and put insulation between the joist and pipe, and did not help. Seems to becoming from the heater. I will say these heaters have flex supplies that are curved back and forth before they tie in the copper pipes. I told the homeowner that I would for sure take them off and hard pipe to the heaters, as they already have been leaking. So I fiqured either the arestors which is what I am going to try, or for a second thought maybe expansion tank. Kinda puzzled, but fiqure one of the two has to work. Thanks for the help


Are you sure it's not just the heater knocking?


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## arkyplumber (Jan 10, 2009)

That is what is sounds like, coming from the heater which by the way is electric.


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## Plasticman (Oct 14, 2008)

check to see if the previous installer used a stop on the cold side or a gate. If its a stop, it could be the washer is loose in it.


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## ONETIME (Sep 19, 2008)

In most cases your hammer arrestors should be installed at the highest point closest to the fixture. If the fixture is fed from above as is the case in most commercial projects you would replace the 90 with a tee and place the arrestor and top end of tee. In a battery of fixtures I will install the arrestors at the end of the battery hot and cold. Does the water heater have a pressure relief tank and a vacum relief valve? This should prevent surging knock as water pressure will fluxuate periodically on the service.


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## arkyplumber (Jan 10, 2009)

Well guys, finished the job yesterday. Put two shock arestors on the heaters, and changed out the flex lines to hard pipe. Everything seems to work great. I did see something new to me before. When I removed the flex lines I noticed on the cold side were little floats at the top of the dip tube. The brand of heater was Reliance. Little plastic float that had a steam on it. I fiqure it is to stop the hot water from going back up the cold side. Just wondered if this was the problem? First time I have seen them before.


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## plumber1a (Jan 3, 2009)

Put a check valve and expansion tank on, it will stop.


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## gabby (Jan 27, 2009)

My pipes in my house creek when you run water up stairs. This is because of the new house plumber drilling to small of holes. It also did not help that they used spray foam around the pipes. I have seen this at my customers houses also, due to bad new constuction practices.


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