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-   -   Water pressure, gallon per minute values in relation to shower output (http://www.diychatroom.com/f7/water-pressure-gallon-per-minute-values-relation-shower-output-89860/)

JasonNY 12-18-2010 12:07 AM

Water pressure, gallon per minute values in relation to shower output
 
I have a question of how the house pressure and the gallons per minute of the rough in valve equate to shower head output that I hope someone can help me with.

My current setup is an older 1980's Moen rough-in valve that when measured with a bucket & timer from the bathtub spout is 12gpm, high incoming pressure (don't know psi, but the garden hose outside is insane) and a waterpik brand showerhead with the legal 2.5 gpm restriction. I am in the process of shopping for plumbing supplies for a full remodel.

Currently even though the showerhead is a 2.5gpm, I tested it with a bucket and stopwatch at 4gpm (filled a 4 gallon bucket in 59sec). I am very happy with this pressure shower and would hate to have a worse shower after a remodel.

My question is what causes the overload to the showerhead to allow 4gpm instead of the regulated 2.5gpm(i've had a few waterpiks on that shower, so I know it isn't a defective one)? Is it simply the high house water pressure or a combination of high pressure and 12gpm valve? The reason I ask is because the only current valve in today's pressure balancing type that produces that much gpm is a kohler K-2971-KS which is mega expensive (almost $300 each). The other 'regular' valves like the Kohler K-304-CS, Grohe 35015 or American Standard valves are 5.5-6gpm @ 45psi and cost under $100 each. So the question is if I used a 6gpm valve like a K-304 with my current waterpik showerhead and same high house pressure would I still get the nice 4gpm output or do I need to buy the K-2971 to replicate the showerhead gpm output I enjoy now?

Sorry for the long post, I wanted to make sure I explained it all correctly. Thanks

nap 12-18-2010 01:03 AM

the 2.5 gpm is based at a specific pressure. If your pressure is higher than the pressure used to determine the flow rating, you will have a higher flow.

while you have a measured output of 12 gpm in the tub, you might try to research that to see if you can determine what it was actually rated for. It too would be affected by pressure just as the showerhead would.

what you might do is adjust the valve to flow the approximate flow of the lesser costing valves and then flip it up to the shower and measure your flow there.

Work4living 12-18-2010 08:42 AM

Jason,

Moen still makes a valve that can meet your water needs. It uses the same cartridge as the one you currently have. It is the moentrol series. It is Temperature & Pressure balanced. As for the high volume. All valves including shower heads have been engineered to actually deliver "adequate" flow.... I prefer moen's line of faucets, mainly because they have met code and still managed to stay "old school" in their water delivery methods.

JasonNY 12-18-2010 12:24 PM

Quote:

Originally Posted by Work4living (Post 553075)
Jason,

Moen still makes a valve that can meet your water needs. It uses the same cartridge as the one you currently have. It is the moentrol series. It is Temperature & Pressure balanced. As for the high volume. All valves including shower heads have been engineered to actually deliver "adequate" flow.... I prefer moen's line of faucets, mainly because they have met code and still managed to stay "old school" in their water delivery methods.

Is it the 3510 you're referring to? Do you know the gpm, it doesn't list it on their site.

http://www.moen.com/m-pact/moentrol-...ONSUMER%3A3510

Work4living 12-18-2010 12:28 PM

Yes, you have the correct series....I dont have the data sheet in front of me, but i believe that valve will produce 12 g.p.m. @ 50 p.s.i.

I will try and find the data sheet. But trust me it is the most flow you will have available for a single shower head. they also have another valve that has a diverter valve above it that allows for a secondary head, hand shower, etc...

JasonNY 12-21-2010 12:08 PM

I picked up a pressure test gauge today and found out my home's pressure is 93psi. Is that abnormally high?

Work4living 12-21-2010 07:43 PM

Jason,

Officially Yes, the pressure is high. Code says anything above 75 psi should have a PRV pressure reducing valve to lower pressure below 75 psi. Personally I know a lot of people who would kill for that kind of pressure.

There are a lot of parameters here more cons than pros. The high pressure can cause water hammer, degradation of plumbing system, failure of fixtures release of safety valves in the waterheater.

I would recommend you get a PRV installed, this will also most likely cause the need for backflow protection.

You'll have to check your municipalities requirements.

Of course the other side is that you replace your shower valve with the Moentrol and not worry about the pressure.

JasonNY 12-23-2010 05:50 PM

I got a reply back from Moen on the Moentrol specs. The gpm is 6.5gpm at 60 psi. Nothing special here, might even be a bit less than the standard Kohler and Grohe valves as their 6 gpm is rated at 45 psi. I think i'll just go with the Grohe valves as im using their faucets and their shower valve trim are the best looking and best value of what i've seen.


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