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Explain to me how to figure design operating pressure please! help

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sprankla

Starting Member

Posts: 1

1

Monday, September 24th 2012, 2:46pm

Explain to me how to figure design operating pressure please! help

Ok ive got my design diagram almost completed, ive submitted it to get a permit but i didnt figure the design operating pressure... I was under the impression since im not a proffessional it wasnt a requirement but i was incorrect about that.

So ive got most of my components (which i ordered from this website's store) but zero of my main and lateral lines which will be 1" mains and what ever is required after that. my valves are 1" hunter valves and a febco 1" PVB, and im using rainbird US-400 4 in. Pop-Up Sprinkler Spray Body's pretty much throughout the entire system with appropriate sprayer heads for each spot.

What is an easy for children to understand method of calculating the design pressure? My static pressure is 72psi, and by my city's permit guidelines i cannot exceed 16 gpm in each zone if that is relevant.

more questions soon.

hi.todd

Supreme Member

Posts: 417

Location: Houston, Texas

2

Monday, September 24th 2012, 6:39pm

Start with how much pressure you need at the sprinkler head (Spray is 30).
Then Work backwards and add all of the pressure that you lose through friction loss of the Meter, Backflow, Valves, Elevation changes, Mainline, Lateral line Piping, and Fittings. This friction loss will depend on how many gallons per minute you are flowing through each valve. Usually a fairly safe number with low friction loss on 1" mainline is 12 Gallons per minute. You will have to do some calculations. :thumbsup:

In my area a Flat Houston, a spray sprinkler system normally has a design pressure of 45 ish LBS.

I may have left one or two things out that I can't think of now, but for your purposes this should suffice.
:thumbup: :thumbsup:

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