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Manifold size

wingsaircharter

Active Member

Posts: 7

Location: USA

1

Friday, August 10th 2007, 1:28am

Manifold size

I am a novice to sprinkler installs but have spent lots of time asking questions and reading up.

I am designing a 110 head 10 zone system for my large yard using sprays, 5000 Rainbirds, and MP Rotators, all on different zones as suggested. I am drawing with a 2 hp pump out of the river.

My question:
I am going to run the Rainbird DV valves with the 1" inlet and 1-1/4 inch barb outlet that supposedly will flow from 2-40 gpm according to Rainbird. (which I don't really understand since 1" and 1-1/4" poly pipe is not supposed to exceed 12gpm and 22gpm respectively without exceeding 5 feet per second)

I have about a 150' run to the valve box that will have 5 zones (extending about another 150 feet) feed out of it. I want to feed that manifold with 1-1/2" poly. It seems that all of the prebuilt manifolds use 1" pipe and then the valves attach to it. My supplier said that the 1" manifold will work fine. To me it seems that the 1" manifold between the 1-1/2" feeder and the 1-1/4" coming out of the valves would be a bottleneck and restrict the flow. My max flow on any one zone is 25gpm which is why I want to feed it with 1-1/2". Any thoughts?

Wet_Boots

Supreme Member

Posts: 3,688

Location: Metro NYC

2

Friday, August 10th 2007, 4:07am

Build your own manifold with 1-1/2" fittings, if you don't want the flow restriction.

HooKooDooKu

Supreme Member

Posts: 685

3

Sunday, August 12th 2007, 1:40pm

Don't thin of valves as a bottle neck (they all are regardles of size) but instead think of them as a source of pressure loss. As long as the valve is designed to handle your expected flow and you can tollerate the valves pressure loss at your expected flow rate, then the size of the valve doesn't really matter.

As an example, the Rainbird 1" PGA valve is designed to handle up to 40 gpm and will lose about 5psi of pressure at 25gpm. You will likely loose about another 1/4 to 1/2 psi for the flow through the reducer fittings to transision from 1-1/2" to 1", but otherwise there isn't anything wrong with using a valve smaller than the average pipe size.
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