PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
(OP)
The PLBG Inspector asked for WHA to be installed on Hot Water branch with two lavatories and in a toilet rm with one lavatory. Both branches do not extend more than 5 ft from the vertical drop.
First I don't consider the lavs as a quick closing valves and I provide WHA only on the Cold Water branches with Flush valves.The PDI WH 201 have examples with Lavs and shows WHA's on the HOT WATER branch. Am I missing something?
Need help in understanding which plumbing fixture will be considered to have quick closing valve and will require a WHA on the hot water line.
Thanks
First I don't consider the lavs as a quick closing valves and I provide WHA only on the Cold Water branches with Flush valves.The PDI WH 201 have examples with Lavs and shows WHA's on the HOT WATER branch. Am I missing something?
Need help in understanding which plumbing fixture will be considered to have quick closing valve and will require a WHA on the hot water line.
Thanks





RE: PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
Generally, I design the cold water lines to not need them either.
Sounds like the inspector is trying to show his authority.
Are the lavatory faucets electronic or manual. Sometimes, the electronic faucets can be considered quick closing. It also depends on what pressure you have in your piping. This seems to affect water hammer at times.
RE: PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
RE: PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
A flush valve flows 25-30 gpm - very quickly so you can get the 1.6 or less gallons per flush.
A private lavatory flows 1.5 gpm, which is typically split between hot and cold so you might have a maximum of 1 gpm in a single pipe. Public lavs flow one third of that so the flows are even lower.
Pipe size is smaller for lavatories than for flush valve fixtures.
I have never done the math for lavatories - I usually design larger manifolds for flush valves so the velocities are low.
RE: PDI WH 201 PLACEMENT OF WATER HAMMER ARRESTORS
Also, even if a shock wave (watter hammer) will not be formed in the pipe from the closure of the valve, there will still be a pressure spike in the pipe which will cause movement in piping that is not properly restrained. I have had a 1/2" pipe (hot or cold) to a lavatory faucet (1.5 gpm) bang against the stud wall when the standard lavatory faucet was closed relatively quickly.
If I saw that arrestors were placed on the cold line to the faucet, then I would question why they are not on the hot.