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Friday, July 26th 2013, 1:05am

Extreme pressure loss

Hello all,

I had a sprinkler system installed recently and I came across an issue I believe may be reducing my performance.

I opted for all Rainbird 1800 PRS SAM sprayers and 5000+ Rotors. We have very high water pressure in our sub division (100+ PSI) so all the homes here have pressure regulators.

I set the pressure regulator to a pretty high 80psi. My issue is that when I turn on any zone except two shrub zones my pressure drops to approximately 30-35PSI.

Zone 1 (shrub zone) - 8 sprayers
Zone 2 (shrub zone) - 4 sprayers
Zone 3 - 6 sprayers (65-70 psi)
Zone 4 - 4 rotors (34 psi)
Zone 5 - 4 sprayers (one is a 18-VAN) (50psi I believe)
Zone 6 - 4 rotors(33 psi)
Zone 7 - 4 rotors(33 psi)
Zone 8 - 8 sprayers(40 psi)
Zone 9 - 9 sprayers (35psi)

It would seem that I have a gpm limitation here but I guess I'm surprised because I have good water pressure. The home is new and has what I believe is a 1" plastic service line going to a 1" ball valve, then a 1" pressure regulator, then a water meter, then another ball valve then a 1" copper pipe to a 1-1/8" pex pipe to another ball valve and then out of the house via 1" copper pipe to the vacuum breaker/backflow preventer and valve box. This interior run of pipe is probably 20 ft.

I am measuring the pressure at a bib that comes off this 1-1/8" pex line with a 1/2" stub.

Is there anything in particular I should look at that might be limiting my water flow. I suppose its possible that they used small diameter water lines for the sprinkler system but I believe he specced out 1" pipe. Can certain valves, vacuum breakers, backflow preventers, pressure regulators or some other device in line severely limit the GPM?

I am possibly going to try changing spray zones to hunter MP rotators but that doesn't fix the rotor zones.

The system works yes, but I'm irritated that I paid for pressure regulated heads but I'm not even exceeding the pressure where they are necessary. I can't imagine someone with my incoming pressure should have this issue.


Supreme Member

Posts: 5,292

Location: Metro NYC


Friday, July 26th 2013, 5:19am

Try increasing the pressure regulator output to 90 psi. Then take inventory again. You may need to try 100 psi.

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