Low GPM - Rotors don't turn?

zr100

LawnSite Senior Member
Location
NH
Usually on a system rescue and I find 3/4" pipe. What Rotors do you like? Hate it when they just won't spin or spin soooo slow. Smaller nozzles don't seem to help much either.
 

Garrett1234

LawnSite Senior Member
I really like the rainbirds. 3/4” puts ya in the 5000 series. However, if lower pressure possibly using a reducer at the sprinkler from 3/4 to 1/2 and running 3500’s could help. I’ve tried a lot of brands, and I find the coverage of the rainbirds to be at the top of the list for coverage.
I will say, some rotors on the same valve rotate at MUCH slower rates than others (i don’t know why nor have i tried to learn why). But the coverage balances out after a zone run time.
 

Wet_Boots

LawnSite Fanatic
Location
metro NYC
Both matter and are tied together of course
They are not tied together. I've installed lowest-flow rotors operating at ridiculously high pressures, because nothing else was going to match the changed output of a well. Of course the client needed a new/redrilled well, but that wasn't in the budget :realmad:
 

magna111

LawnSite Senior Member
Location
NJ
I’ve found RB 5000s to be unreliable below 1.5 gallon nozzle. If water/pressure is really borderline, 5000s also require a lot more water to seal than a new pgp.
 

Love the Green Biz

LawnSite Fanatic
Location
NYC Metro Area
I’ve found RB 5000s to be unreliable below 1.5 gallon nozzle. If water/pressure is really borderline, 5000s also require a lot more water to seal than a new pgp.
That's a great reason to keep a few RB SAM rotors on the truck. Place the check valve rotor first on the lateral or the lowest point if grade is an issue. Use several if need be.
 

Love the Green Biz

LawnSite Fanatic
Location
NYC Metro Area
I really like the rainbirds. 3/4” puts ya in the 5000 series. However, if lower pressure possibly using a reducer at the sprinkler from 3/4 to 1/2 and running 3500’s could help. I’ve tried a lot of brands, and I find the coverage of the rainbirds to be at the top of the list for coverage.
I will say, some rotors on the same valve rotate at MUCH slower rates than others (i don’t know why nor have i tried to learn why). But the coverage balances out after a zone run time.
The why is usually due to pipe sizing. If you are undersizing the lateral and not keeping pipe size up on the run forcing volume through will reduce the base pressure at each succeeding head. Rule of thumb is to size pipe so that the furthest head's base pressure is only 10% or less of the pressure at the first head. PR will suffer the further out you go due to severe pressure reduction at the base.

Buy a pitot tube and try it out at each head-and do it on one of those hot days. Refreshing!
 
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Love the Green Biz

LawnSite Fanatic
Location
NYC Metro Area
I remember the old days when Impact rotors worked OK down to 20 psi at the base. This was especially true of the plastic impacts such as RainBird Mini and Maxi Paws and the Nelson series.

It made installing on shallow wells a go as they not only ran "well" but purged small aggregate better that gear drives.
 

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