New Shower Low Pressure and Flow

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  #1  
Old 04-09-13, 07:07 PM
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New Shower Low Pressure and Flow

I would very much appreciate advice on whether the shower in my new professionally remodeled bathroom is operating correctly. When the project was completed, I took my first shower and was disappointed with the weak shower spray. The plumber came to see it and said it seemed ok to him and that he installed it per minimum code. Not being satisfied with that answer, I bought a pressure gauge and did some experiments.

First the specs:
main water line in basement
Static pressure = 60-65 PSI (varies a little bit)
pex to 2nd story bathroom 24 vertical and 30 horizontal with 1 shutoff valve and 5 elbows on hot and cold each
American Standard R110 pressure balance valve

I compared the pressure and flow in my remodeled bathroom to a shower in the basement that was plumbed off the main line with 8 of PEX but does not have a pressure balancing valve.

BASEMENT

Directly out of a nipple:
0 psi, 6.6 gpm (2-1/4 qt in 5 sec)

Shower head
53 psi, 3.0 gpm (2-1/4 qt in 11 sec)

MY NEW BATHROOM:

Directly out of a 1/2" nipple
0 psi, 2.6 gpm (2-1/4 qt in 13 sec)

Shower head
20 psi, 1.9 gpm (2-1/4 Qt in 18 sec)


Bath filler (aka tub faucet)
0 psi, 3.0 gpm (2-1/4 qt, 11 sec)


This seems bad to me. My guess is that the pressure drop for the PEX is maybe 10 PSI at 3 GPM and the pressure drop across the pressure balancing valve would be about the same. That should give me more in the neighborhood of 2.5-3.0 GPM at 35-40 psi. What do you think? Am I missing something or is there a problem. My suspicion is that the pressure balancing valve is bad or obstructed or maybe there is an obstruction in one of the lines going up to the bathroom.

I look forward to any information you can provide.

Bill
 
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Old 04-09-13, 07:25 PM
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I would say the lines to the upstairs are too small. Should have been 3/4". Probably would not pass a plumbing inspection....

Static pressure = 60-65 PSI

Whats the psi with a few fixures running ? Is there a PRV valve in the home?

Was that pex always there?
 
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Old 04-09-13, 07:30 PM
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It did pass inspection. 1/2" is minimum code. I agree that 3/4" would have been better, but I don't think this is giving me more than a 10 PSI drop. I did not measure pressure and flow anywhere else besides the shower in the basement and the shower in the 2nd floor bathroom.

No, there is not a PRV anywhere in the house. This is the pressure coming into the house. It just goes up and down a little bit during the day.
 
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Old 04-09-13, 07:45 PM
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I should have also added:
- The PEX is new as part of the bathroom project. 3/4" main to 1/2" dedicated PEX up to the bathroom. Only things on this 1/2" line are the shower, the lavatory sink, and the toilet. Does not exceed max fixture units.

thanks
 
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Old 04-09-13, 08:20 PM
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Did you take the restrictor out of the shower head? Put it back in if you did.

guess is that the pressure drop for the PEX is maybe 10 PSI at 3 GPM and the pressure drop across the pressure balancing valve would be about the same. That should give me more in the neighborhood of 2.5-3.0 GPM at 35-40 psi. What do you think?
Yes and add up the fittings too.

3/4 you would probably only lose 2 psi or so plus fittings. Less frinction on larger fittings too.

I will have to check code. At a min we always had to run 3/4 risers to the upstairs.

If you think its the cartridge have the plumber change it..... I feel your lacking volume with the 1/2 pipe at that distance.....

Lastly put low GPM heads/aerators on. Youll get better pressure if your trouble shooting does not turn up anything.

I find it funny that a plumber would do minimums. he should know about psi/volume issues with piping an upstairs... Geez the materials cost the same....
 

Last edited by lawrosa; 04-09-13 at 09:57 PM.
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Old 04-09-13, 09:00 PM
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Code minimums are just that, minimums. I agree with Mike that the riser to the riser should have been no less than 3/4 inch and using PEX I would have gone with a one inch. I suspect that you WILL have serious problems if someone is taking a shower and another person flushes the toilet

Also, that 24 feet rise in elevation is losing you at least 10 psi, maybe as much as 12 psi so your working pressure is really somewhere between 48 and 53 psi.
 
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Old 04-10-13, 03:43 AM
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I checked a couple of AS spec sheets for various trim kits. The GPM you are showing are within what AS shows as normal. I looked at one trim kit (Colony) that showed less than 2 GPM at 100 psi. It also showed better flow rate out of the tub spouts.
 
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Old 04-10-13, 04:01 AM
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Thanks for this info. I accept the flow limiting, whether it is 2 gpm or 2.5 gpm. But, shouldn't the shower pressure be higher? Am I correct in thinking that a 2 GPM shower at 40 PSI will work better and feel better than a 2 GPM shower at 20 PSI? And, if the upstairs shower is 20 PSI and the basement shower is 53 PSI, is there a problem somewhere? (eg bad pressure balancing valve, obstruction somewhere, etc)?
Bill
 
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