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rob613 03-14-2013 12:08 PM

pressure and shower faucet
I am having a problem with occasional drips from a shower head with a relatively new shower faucet. The faucet has both a pressure balancing unit and a temperature control cartridge. I've already tried changing them both out.

I temporarily put a pressure gauge in place of the shower head and I see a regular pressure of 65 psi with occasional bursts of up to 120 psi if a sink faucet is shut off abruptly. I also see some minor pressure fluctuations due to things outside of my house.

Interestingly once I have at least 40 psi in the gauge, even if I shut off the shower faucet, the pressure continues to rise to 65, and the pressure bursts come through as if the shower faucet were open.

What should be the expected behavior in the presence of pressure wave slams?

Should a faucet cartridge maintain a positive shut off even with pressure bursts? I think the faucet is designed for up to 100 psi - perhaps there is a standard margin for temporary bursts above that?

Also, I understand that the plumbing code prevents putting a complete shut off at a shower arm. Is this due to risk of hot water mixing back into cold water that could come out a sink faucet? What is the risk?

joeplumber85 03-14-2013 07:12 PM

If you abrubtly shut-off any fixture you cause water hammer within your potable water system which can lead to damage to nearby piping and appliances. That said, that occurs more-so with solenoid valves in appliances like dishwashers and washing machines, and if it's causing a new shower diverter to act up that would be a first for me.

Most likely you have:
A) improperly installed the cartridge
B) have debris plugged up in the cartridge letting water through
C) have pressure issues due to thermal expansion or a busted PRV and it's damaging the cartridge.

99% of fixtures are designed for 65 psi to a MAX of 80 psi. Anything higher is damaging to components and voids most warranties.

rob613 04-18-2013 12:07 PM

Kudos to American Standard - problem fixed
The problem behind this thread has a very happy ending. I would like to thank the customer service managers at American Standard for standing by me through this problem, going way above and beyond what anyone could expect.

I was recently sent a newly redesigned pressure balancing valve with larger rubber o-ring seal pieces which seems to have been the final piece needed.

Apparently this new part can actually withstand a temporary pressure burst of a few hundred PSI.

It has been interesting to diagnose what was going on, and I also thank those who commented on this thread.

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