# Commercial Tank Banging



## Catlin987987 (Nov 12, 2010)

I was called to a call for "banging pipes". It is a 4 story 24 unit appartment building and the Hotwater tank is on the top floor with the boiler. Its a newer Bradford white (maybe 80us Gallon) installed withing 1 year, and from the floor below it you could hear it banging and thumping. I checked the gas pressure and I flushed the tank, still banging.

It is piped correctly and it vents nicely, there is no water issues and when flushing the tank not much sedimant came out. The SRV is not dripping.


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## plbgbiz (Aug 27, 2010)

Banging noises on hot water systems always make me think check valve.


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## evilcyrus (Apr 27, 2009)

shes done! it wont go away


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## OldSchool (Jan 30, 2010)

Could be thermal expansion.....


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## Catlin987987 (Nov 12, 2010)

OldSchool said:


> Could be thermal expansion.....


 WOULDN'T THE SRV GO THEN? 
Its so loud I can hear it from the floor below and this is a concrete building. its not the checkvalve, I had isolated the recirc line and no differance


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## OldSchool (Jan 30, 2010)

I would check the water pressure it might be just below the relief valve setting. 

Is there an expansion tank on this hot water tank.....

The only reasons this could happen (shaking or banging) is if water was flashing to steam or the pressure was rising in the tank...

flashing to steam could be caused by a restriction in the pipe.


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## Catlin987987 (Nov 12, 2010)

No expantion tank. How would you check id there was a restriction on the cold line? There was plenty of pressure coming when I was flushing, could I throttle the hot? Maybe tuning down the temp? Is there a way to set a differental for when it fires and its set point? You shouldn't be able to draw off more water then what is feeding the tank


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## accobra88 (Nov 8, 2010)

Expansion tank ... is there a hot water loop on the inlet side.


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## Catlin987987 (Nov 12, 2010)

any Ideas? Bradford White has not phoned my back yet


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## Protech (Sep 22, 2008)

Did you isolate the check valve from both sides? Pull the cover on the valve and wedge a piece of bailing wire or somthing across the valve seat to hold the valve open. Run water. If no banging, it's the check valve.


To check for flash off: check water temp. If it is higher than 160, you have a problem with the thermostat.

Also, it could water hammer. If you're getting hammer somewhere, the pressure wave can resonate back to the tank and the tank can act like a speaker cone(even more so if there is good contact with the slab that will further enhance acoustics).


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## 1703 (Jul 21, 2009)

I know you said its not the check valve, but share this anyway-

I was repairing a sloan valve in a public restroom. Any time a stool was flushed, something would bang, and I mean BANG.

Got to looking around and found a swing check above the ceiling on the verical part of the DHW return line. Check would lay open, and for what ever reason, a sudden quick draw usage would SLAM the check closed.

Put the check on the horizontal, no more bang.


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## Catlin987987 (Nov 12, 2010)




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