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Starting Member


Thursday, August 11th 2011, 9:55pm

Funny Pipe Flow Rate

Our city has untreated water for irrigation systems, but I only have 48 psi at the best, and 40 psi when a lot of folks are watering. Naturally I plan on setting my timer outside of the heaviest usage time.

Using 1" sch-40 PVC, I can get 13 gpm, but I can't find anywhere what flow rate you get at 40 and 50 psi through a foot of 3/8" ID funny pipe with their 3/4" L-connectors on each end. I'm just looking for a ball-park figure. Hopefully 3-4 gpm.

Orbit is a local company and their design gives me two zones for my approx 40' x 40' front yard. One with a Voyager II head in each front corner, and the other zone with three Voyager II heads along the front of our house and drive due to the 4'x12' walkway from our driveway along the side of the attached garage leading to our front door.

If you have the answer, or first hand experience with this kind of low pressure, please share your knowledge.

tia :S


Supreme Member

Posts: 493

Location: Seattle


Friday, August 12th 2011, 12:36am

Keep your 1" pipe and then branch off with funny pipe to the head. Try not to do more then 18" of funny pipe but it's not the end of the world if you do a bit more.

Central Irrigation

Supreme Member

Posts: 371

Location: Central Minnesota


Friday, August 12th 2011, 7:51am

At 3 GPM you will lose .4 PSI per foot

At 4 GPM you will lose .8 PSI per foot

Taken from Irritrol's website.


Advanced Member

Posts: 67

Location: South Jersey


Friday, August 12th 2011, 8:01am

If you keep your funny pipe short enough you shouldn't need to really worry about the pressure drop you would get from it. Concentrate on keeping your main line and laterals the correct size for your pressure and flow rate.

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