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 Understanding PEX pressure loss
Author: biship (NJ)

I'm having a new house built and the plumber just put in a parallel distribution PEX system.
He put 3/8"s almost everywhere and I am trying to understand if it will be problematic.

I have runs of up to 90ft, and an unknown rural city supply water pressure (60-70PSI?).

The PEX design guide illustrates the loss of pressure per gal/m per 100 feet.
[www.huduser.org]




I did some estimates for my house:

(calculations are for just the single cold supply).

Does this mean if I turn on the first 2 faucets, I will see a combined ~50PSI loss in the system?

From what I read, when a system goes under 40PSI, you will notice reduced flow rates.
This means a 3rd faucet will lower the flow rates of all 3 faucets considerably.

Is this how to interpret water pressure?
Thanks for all your help smiling smiley

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 Re: Understanding PEX pressure loss
Author: hj (AZ)

it means if you have a 3/4" supply to the manifold, you will see the pressure drop for 4 gpm or about 5psi. You are calculating the drop for each faucet, but they are not cumulative unless they are on the same pipe. Every section has to be calculated independently depending on the flow through it.

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 Re: Understanding PEX pressure loss
Author: biship (NJ)

Thanks hj. How does a plumber calculate the pressure loss port manifold per outlet, and when multiple are opened?

Post Reply

 Re: Understanding PEX pressure loss
Author: hj (AZ)

WE don't. We use "intuition".

Post Reply





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