# Pressure Vacuum Breaker and Hammer Arrestor Help.



## LeakMan (Mar 7, 2011)

So, my company has finished up a large project in a lab. 1 month later we get a call saying the PVB failed and flooded 3 floors. Were all confused at this point and wounder what the culprit was. Possibly trash, or even worse, pressure spikes up to 120psi which is the "breaking point" on wilkins 460 PVB.
Should placing a Hammer Arrestor before the PVB eliminate the burden on the PVB or should one be placed downstream from PVB? Any answers are good answers, and thanks for the help.


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## gusty60 (Oct 21, 2008)

Any possibility that it froze?


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## LeakMan (Mar 7, 2011)

No it didn't freeze because it's located inside above a fume hood. I thnk I fouf an application that will work.

------check valve-------------1 1/2" pressure reducing valve---------------to branch lines.

We believe it was the pressure spike slapping the check disc after the psi dropped dangerously low allowing the air relief to open and SlAM shut causing damage.

Thanks for responding.


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## Tommy plumber (Feb 19, 2010)

LeakMan said:


> So, my company has finished up a large project in a lab. 1 month later we get a call saying the PVB failed and flooded 3 floors. Were all confused at this point and wounder what the culprit was. Possibly trash, or even worse, pressure spikes up to 120psi which is the "breaking point" on wilkins 460 PVB.
> Should placing a Hammer Arrestor before the PVB eliminate the burden on the PVB or should one be placed downstream from PVB? Any answers are good answers, and thanks for the help.


 



Because no provision was made for drainage under the PVB, I would remove and install a double check valve in place of the PVB. A double check valve will not vent to the atmosphere.

Anti-spill PVB's are available, by the way.


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## PlumbThis1 (Apr 15, 2010)

We have hundreds of them on campus that feed the internal water on fume hoods. I would talk the lab owners and put in a seperate RP that feed the hoods. The PVB will not stop leakeing, the pressure difference gets to them here, and our water is a little on the hard side. Or you could tell them to order a case of repair kits and write your phone number on the hood.


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## Redwood (Sep 8, 2008)

Try Reading This... See if you can follow the directions... :whistling2:

http://www.plumbingzone.com/f3/why-post-intro-11368/


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## ToUtahNow (Jul 19, 2008)

Regardless of whether it was debris in the line or a pressure spike even a spill-resistant PVB can leak so you must provide a means of drainage below it. A double check is not a solution as it does not afford the same protection as a PVB. You either need to provide a means of drainage below the PVB, move the PVB where it can not cause damage or increase your insurance coverage. After the above is solved then you can look for the reason it spilled.

Mark


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