# Hammer Arestors



## Bill (Jun 17, 2008)

I noticed a lot of people use a section of pipe above the washer box as a hammer arrestor. Is this better than using the factory ones you can buy?


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## drtyhands (Aug 16, 2008)

Our inspectors in my area won't accept the air chambers.They want to see mechanical hammer arrestors.A few hundred miles north of here they're putting them on everything from what I here.


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## 22rifle (Jun 14, 2008)

I want to do a test. I need clear tubing of some sort. maybe the clear PEX?

I am going to install air chambers on my tub and watch to see how long until the air is absorbed. 

Anyone have any ideas on how I should do the test?

1/2" or 3/4"

I assume 12" air chambers. Right?

Shall I use clear PEX? It isn't really clear but you could see the water level I think.

Anyone interested in the results?


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## gear junkie (Jun 20, 2008)

I would be. What if you used colored water? I've never seen clear pex before.


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## Bill (Jun 17, 2008)

22rifle said:


> I want to do a test. I need clear tubing of some sort. maybe the clear PEX?
> 
> I am going to install air chambers on my tub and watch to see how long until the air is absorbed.
> 
> ...


Umm, did someone wake up on the wrong side of the bed:whistling2:


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## user4 (Jun 12, 2008)

22rifle said:


> I want to do a test. I need clear tubing of some sort. maybe the clear PEX?
> 
> I am going to install air chambers on my tub and watch to see how long until the air is absorbed.
> 
> ...


Water hammer would not be all that noticeable, if at all, using plastic pipe.


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## gear junkie (Jun 20, 2008)

I think this is not to test the idea of water hammer but the theory that water absorbes the oxygen making the arrestor water logged and useless. I know that happens but I'm curious to see how fast this happens. I've always been taught that arrestors are to be 18" btw.


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## 22rifle (Jun 14, 2008)

USP45 said:


> Umm, did someone wake up on the wrong side of the bed:whistling2:


Huh? I didn't mean anything negative against you. Or anyone. I just keep claiming they are a waste of time and money and few people believe me.


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## user4 (Jun 12, 2008)

22rifle said:


> Huh? I didn't mean anything negative against you. Or anyone. I just keep claiming they are a waste of time and money and few people believe me.


Using the piping systems you install for water pipe, they are.

Using the material I use to pipe a condo, they are not.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> Water hammer would not be all that noticeable, if at all, using plastic pipe.


It's not to test water hammer, but the rate the water absorbs the air cushion.

The rest of my system is iron pipe and copper. The only thing that would be PEX is the air chamber.

Do you have any better ideas for the pipe I would be using?


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> Using the material I use to pipe a condo, they are not.


You mean copper?

My house is galvanized and copper.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> Using the piping systems you install for water pipe, they are.
> 
> Using the material I use to pipe a condo, they are not.


BTW, what would constitute a waste of time and materials in your opinion?

Can we agree on a standard here? If the air cushion is absorbed in 90 days? Would you consider that a failure of the intended purpose of the air chamber?


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## user4 (Jun 12, 2008)

22rifle said:


> BTW, what would constitute a waste of time and materials in your opinion?
> 
> Can we agree on a standard here? If the air cushion is absorbed in 90 days? Would you consider that a failure of the intended purpose of the air chamber?


My point is this, using PEX is not going to prove your point, because the loss of the cushion is going to be affected by the give in the water line itself, you are not conducting a sound scientific test.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> My point is this, using PEX is not going to prove your point, because the loss of the cushion is going to be affected by the give in the water line itself, you are not conducting a sound scientific test.


OK, do you have an alternative suggestion that would be transparent and meet your criteria?

BTW, 1/2" or 3/4", 12" or 18"?


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## user4 (Jun 12, 2008)

22rifle said:


> OK, do you have an alternative suggestion that would be transparent and meet your criteria?
> 
> BTW, 1/2" or 3/4", 12" or 18"?


You can get clear sch 80 threaded plastic pipe, the price is outrageous though.

12" air chamber at every opening, and a 24" air chamber on the top of every riser.


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## 422 plumber (Jul 31, 2008)

I believe residential air chambers are useless on metal pipes. They fill up over time. The mechanical one work great. Actually, if the the pressure is kept below 80 and the pipes are sized right, you don't need them. Most water hammer is a function of undersized pipes and high pressure.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> You can get clear sch 80 threaded plastic pipe, the price is outrageous though.
> 
> 12" air chamber at every opening, and a 24" air chamber on the top of every riser.


OK, so are you saying that if I put a 12" air chamber on the hot and cold of my tub, you would not consider the results to be valid unless the rest of the fixtures each had one too?

Just making sure I understand you here.

Also, would you consider them to be a failure if they filled with water in 90 days?


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## 22rifle (Jun 14, 2008)

jjbex said:


> I believe residential air chambers are useless on metal pipes. They fill up over time.


There are a lot of very intelligent plumbers who disagree with you on this. 

Then there are also those who do agree but just say, well, drain the water lines periodically.

I am trying to figure out under what conditions they would accept evidence of a failure.


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## user4 (Jun 12, 2008)

22rifle said:


> OK, so are you saying that if I put a 12" air chamber on the hot and cold of my tub, you would not consider the results to be valid unless the rest of the fixtures each had one too?
> 
> Just making sure I understand you here.
> 
> Also, would you consider them to be a failure if they filled with water in 90 days?


If you are cherry picking where to use them and where not you are setting them up to fail now aren't you?


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## 422 plumber (Jul 31, 2008)

One of my apprentice instructors told us that some organisation plumbed a module house with glass pipe, for testing purposes. The air chambers filled up in about 6 months. Bullshit? Maybe. I will do a google search and see what comes up. I do know that when I remodel and cut out copper for scrap, the airchambers always have water in them. It is pulling a vacuum and doesn't come out until I am cutting the solder joints out, so maybe there is a small pocket of air left.


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## 422 plumber (Jul 31, 2008)

Read this. I know it's biased, but still very informative. 
http://www.siouxchief.com/PDF/whaengrt.pdf


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## Double-A (Aug 17, 2008)

I can't quote anything off the top of my head, but I think if you look, you will find that ASTM does not accept air chambers in lieu of gas charged hammer arrestors.

The reason is the air is dissolved into the water quite rapidly. In as short as weeks according to some studies.

I don't know what our code says, I haven't bothered to look it up. I do think that if you don't get at least a year of protection from air chambers then yes, they are a waste of time to install them, unless you're using them for strapping or aligning purposes, and not as a means to act as a hammer arrester.

If you want to test this, just put a schrader valve on the thing and press it slightly once in a while, you'll know when you get water as opposed to air.

If this still doesn't make sense to you, then consider how expansion tanks are built. They have a bladder to separate the air from the water to prevent it from being absorbed.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> If you are cherry picking where to use them and where not you are setting them up to fail now aren't you?


That's BS. If it's going to fail in one area it will fail in another. 

Besides, even if it fails in one area, wouldn't you want to know that?

BTW, I am opening the wall there to replace the shower valve soon. That would be the only reason I would choose that location.


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## user4 (Jun 12, 2008)

22rifle said:


> That's BS. If it's going to fail in one area it will fail in another.
> 
> Besides, even if it fails in one area, wouldn't you want to know that?
> 
> BTW, I am opening the wall there to replace the shower valve soon. That would be the only reason I would choose that location.


If you are not using them on every outlet like I am is it a fair comparison?

No, it isn't.


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## Bill (Jun 17, 2008)

The reason I asked was because there was some pix here of work and I could had sworn I saw air chambers above the valves in the pix. Thought maybe there was something to it, also seen it done a few times.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> If you are not using them on every outlet like I am is it a fair comparison?
> 
> No, it isn't.


I am not trying to compare it to your job. Hey, your code requires them so I have no issue with you.

All I want to do is see for myself how long it goes before one of them fills up.


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## user4 (Jun 12, 2008)

22rifle said:


> I am not trying to compare it to your job. Hey, your code requires them so I have no issue with you.
> 
> All I want to do is see for myself how long it goes before one of them fills up.


Used according to my code, about eight years.


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## 22rifle (Jun 14, 2008)

Killertoiletspider said:


> Used according to my code, about eight years.


Got documentation?

Is your code different than the UPC in this regard?


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## user4 (Jun 12, 2008)

22rifle said:


> Got documentation?
> 
> Is your code different than the UPC in this regard?


No, just experience.

Chicago code is an animal unto itself, not many codes can even aspire to be as anal and narrow minded as Chicago's plumbing code. This is a code that allows PVC water pipe to feed an irrigation system, but all horizontal sections of said pipe have to be continuously supported, you basically have to build a shelf to support the pipe, and then strap the pipe to the shelf every 18". That is the code for a single family home BTW.


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