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New Member


Friday, March 5th 2004, 6:44pm

seeking advice

****o, I am planning an install, the meter is .75" with 75 psi,
havent done flow yet, its in a new subdivision with more houses goin in, My main line has a 600' run, 10 zone, I was planning on using 1.25" pvc main, and 1" laterals, going thru a 1" backflow preventer, is the 1.25" main overkill, will it hurt anything.
thank you

Tom M

Starting Member


Saturday, March 6th 2004, 5:12am

600' mainline?, wow, how big is the property?

1.25 is not overkill, however how much flow are you designing for?

You may be able to do a "looped" main, that is you can have a mainline that basically forms a circle around your property. If that mainline is 600', you can figure your pressure losses at half of that, or 300' in this case. By doing so, you may be able to use 1" pipe instead of 1.25".


New Member


Saturday, March 6th 2004, 6:09am

Thanks, I think I need to refigure some things.


Supreme Member


Saturday, March 6th 2004, 4:46pm

Agreed, 1.25" is NOT overkill.

If you're mainline is really going to be 600' long, a 1.25" pipe is going to lose about 10psi over a 600' run assuming you've designed for about 15gpm flow.

As for the suggestion of a "looped" main (which depending upon what type of configuration we're talking about, I'm assuming that could double the amount of mainline pipe to be installed), you can cut your pressure losses in half by installing a 1.5" main rather than 1.25" (again, assuming a designed flow of about 15gpm). Accomplishes the same thing.

I'm assuming about a 15gpm flow rate because I think that's getting towards the max possible with a 3/4" meter. Here's an approximate chart for water velocity and friction losses per 100' of Sch40 PVC @ 15gpm:

0.75" - 9fps, 16psi (flow velocity too great)
1.00" - 6fps, 05psi (flow velocity still too great)
1.25" - 3fps, 1.5psi
1.50" - 2+fps, 0.65psi
2" - 1.4fps, 0.2psi

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