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Old 12-13-2015, 09:51 PM   #1
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Water hammer arrestor?


Going to be adding a urinal to my basement with ProPex supply lines.

My house has an expansion tank right after the meter: and there doesn't seem to be any arrestors on the existing copper lines (washing machine... Dishwasher.... Etc....).

Is a hammer arrestor needed? Or would the expansion tank do the work of the arrestor?
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Old 12-13-2015, 11:20 PM   #2
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Yes, they are needed and required--

UPC-Uniform Plumbing Code
609.10 Water Hammer. All building water supply systems in which
quick-acting valves are installed shall be provided with devices to
absorb the hammer caused by high pressures resulting from the
quick closing of these valves. These pressure-absorbing devices
shall be approved mechanical devices. Water pressure-absorbing
devices shall be installed as close as possible to quick-acting valves.

IPC-International Plumbing Code
604.9 Water Hammer. The flow velocity of the water distribution
system shall be controlled to reduce the possibility of water hammer.
A water hammer arrestor shall be installed where quick-closing
valves are utilized. Water hammer arrestors shall be installed in
accordance with the manufacturer's specifications. Water hammer
arrestors shall conform to ASSE 1010.

http://media.wattswater.com/F-WHA.pdf
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Old 12-14-2015, 06:46 AM   #3
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An expansion tank will absorb the shock that water hammer arrestors are intended to absorb but the tank would need to be installed at the urinal or other device with the fast closing valve. It would be awkward because there cannot be more than an inch or two of pipe connecting the expansion tank to the main line.

The expansion tank will still perform the job of absorbing the expansion of the tankful of hot water as long as there is no closed valve between it and the water heater. But inspectors want an expansion tank above the water heater where it is easier to see (as being present).
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Last edited by AllanJ; 12-14-2015 at 07:01 AM.
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Old 12-14-2015, 08:23 AM   #4
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I understand. I was reading the Uponor manual after I posted, and they mention that because ProPex is quieter than copper, and flexible, that a hammer arrestor isn't required (unless code specifies it).

Of course I can't seem to locate any Uponor water hammer adapters (which other PEX companies offer.

And I was trying to maintain a 1" supply to the urinal to maintain flow: I'm guessing I'll have to add another T (already two in the line), and then add a female threaded adaptor to accept an arrestor. I can't see any other way to make it work...
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Old 12-15-2015, 07:03 PM   #5
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Look up Sioux Chief water hammer arresters. They are the best in the industry.
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Old 12-15-2015, 09:14 PM   #6
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Quote:
Originally Posted by dannyoung85 View Post
Look up Sioux Chief water hammer arresters. They are the best in the industry.
But how would you integrate it into a ProPex line?
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Old 12-15-2015, 10:12 PM   #7
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My understanding of water hammer is that it's due to the momentum of the water being transferred to the pipe the water is moving in. The faster the water movement stops, the more the momentum of the water is transferred to the pipe instead of being dissipated in other ways. If it's a rigid pipe like iron or copper, then that pipe is going to bounce around and shake and knock against the studs and joists it's fastened to, thereby causing the water hammer noise.

But, if the water is moving in a Pex pipe, then the Pex pipe would flex and bend a little bit, but you wouldn't have the same shaking of the pipe against the studs and joists as you would with iron or copper pipe, so you wouldn't get the noise. So, maybe the code is simply out of date and doesn't reflect the fact that you probably wouldn't even need a water hammer arrester with Pex piping.

I'd talk to some plumbers in your area and see if the local inspectors want to see a water hammer arrestor even on Pex piping.
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Last edited by Nestor_Kelebay; 12-15-2015 at 10:17 PM.
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Old 12-15-2015, 10:46 PM   #8
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They make them with male threads so you could use a female adaptor. They also sell them with pex ends on them that you could crimp to. Or you could get a regular end one and buy a capper sweat by pex adapter and sweat it onthe hammer arrester.
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Old 12-15-2015, 11:03 PM   #9
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The stub out for the flush valve should be copper.
If the main water line is below the valve stub in the wall, use a copper tee at the top of the riser to the valve stub. In the top of the tee- add a sweat arrestor, the horizontal branch will supply the valve. Bottom of the tee can be a pex adapter going to the 1" main
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