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Wednesday, May 20th 2009, 2:27pm

Valve Manifolds (Multiple or single)

I would like to install a in ground sprinkler system. The System includes a system with 1" copper through a WAtts RPZ .009. I'm planning for 11 zones, 6 in the front/side and 5 in the back/side. My measured PSI is 65PS (WATTS RPZ indicates 12 PSI loss)

From the RPZ to the farthest point in the front yard is 120 ft, and farthest point in the back yard is 225 feet, should I install one 6 port maifold for the front yard and one 5 port manifold in the backyard? The manifolds would physically exist about 110 - 120 feet apart.

Basement-->1 1/4" Copper through wall to exterior ---> WATTS RPZ 1"--> 1' Copper ---> 1" PVC Mainfold1(frontyard(next to RPZ)) ----------PVC40(110/120feet)--------Mainfold2(backyard).............Then off to heads...

Should I place all of the manifolds in one place and run the Poly Pipe to front and backyard?

Newbie DIY... In advance thank you. I have been using as a study guide, but nothing replaces experience.


Supreme Member


Friday, May 22nd 2009, 8:52am

I'm just a DIY irrigation person as well, but my first though is multiple manifolds.

For one, as long as only one valve is on at a time, it doesn't matter if you have one manifold, two manifolds 500' apart, or seperate valves at every zone. You still have to deal with the basics of how much pipe the water is travelling in at what speed (to get friction losses) plus the loss of pressure through the valve. It doesn't mater where the valve is (close to the water source or close to the zone) the calculations are the same.

So I guess I would approch it not so much from minimizing manifolds, but perhaps minizing pipe. After all, if you put the manifold in the back yard, you are going to have to dig a huge trench to fit all the pipes for each ciruit that will all follow the same starting path from the backyard to the front yard. (i.e. why bother putting a manifold of five valves "over here" when the pipes for all five circuits follow the same path for the first 200' before they split off "over there". In that case, it makes much more sence to run a single mainline from "here" to "there" and place the manifold "there".

Also, depending upon the size of area's you are dealing with, don't discount the notion of no manifolds. Instead, run mainline to the start of each zone, and then have a single valve in a single valve box at the zone. The only negative I've seen with this sort of plan is that wiring costs will likely increase since you will have to get wire suitable for direct burial, and use a lot of it. Having a single manifold near the control point obviously makes for a lot less wiring.

Another potential plus for one valve at the zone... if you can manage to place the valves in one of those 6" round valve boxes, grass will grow over enough of the cover to make it nearly invisible. But if you use the large 14x16" "meter" boxes to place your valves in, they are so big that the grass will never be able to completely hide it.

So I guess my best advice is allow for multple manifolds (perhpas more than just two) and start will looking at plans that minimizes pipe and perhaps more important minimizes trench digging.

For one, there is the simple economy of minimizing pipes.

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