Required pipe size based on W.S.F.Us

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Cyphie

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I am building a house served by a well. The well pump cycles on at 40 and off at 60 psi. As I read Appendix P of the 2018 IRC which governs the area I am building in, paragraph AP201.1 2 states "Obtain the minimum daily static service pressure [psi (kPa)] available (as determined by the local water authority) at the water meter or other source of supply at the installation location." Based on that what static pressure do I use when calculating pipe sizes? If I use the low 40 and subtract out height losses I am starting at 31 psi. This seems like the wrong starting point.

So, with more research, I think I figured it out. Since I am using a well, I should use pressure loss across the system to calculate pipe size.
 
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Breplum

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I have no experience with wells, but I would use the chart related to 30 psi static since that is your worst case operating pressure unless you also have a pressure vessel or CSV.
 

Cyphie

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I have no experience with wells, but I would use the chart related to 30 psi static since that is your worst case operating pressure unless you also have a pressure vessel or CSV.
Thanks for the input. I found an interesting link that specifically discusses wells. Conducting the calculations with this method yielded similar results but was a bit less restrictive when it came to determining WFSUs allowed with longer runs of piping. https://dsps.wi.gov/Documents/Programs/Plumbing/SBD8036P_SizingWaterSupply.pdf
 

Jeff H Young

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its expected to use a 3/4 pipe all the way to a 3/4 x1/2 90 at the stub out if it sizes out to 3/4 pipe
 
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