# Funny pipe on one inch inlet rotors??



## Amosjdg (Jul 28, 2019)

Hey guys got a somewhat complex job going on. The area is roughly one acre of land. It will be using a 5hp booster pump to run 12-13 heads at a time at roughly 10 gpm. My question is this...is it a problem to use funny pipe. The smallest part of the line is 1 inch and the largest is 2 inch. The funny pipe fittings even with 3/4 fittings reduces down to to 1/2 at the elbow. Do you think it's a problem going from 1 inch line to 1/2 funny pipe back to 1 inch sprinkler? Will there be a significant volume loss restricting down to 1/2 inch at the sprinkler which has a 1 inch inlet?


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## g-man (Jun 15, 2017)

It all depends on the gpm at the heads, the length of funny pipe and the pressure your system has.


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## Amosjdg (Jul 28, 2019)

System is sized for 10 gpm per nozzle a minute at 70 PSI. Guess I'm just wondering if I should go with a 3/4 inlet sprinkler instead of a 1 inch. Funny pipe won't be longer than 12 inches


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## Delmarva Keith (May 12, 2018)

Just from memory, 1/2" pipe way too small for 10 GPM. I think 1/2" is more like 5 and that was optimistic.

Rainbird publishes design guides that will step you through the calculations. For the main and start of the laterals you are talking about 130 GPM. A wrong choice and ending up undersized and you will be sorry. Either it won't work as intended or the fittings will erode as if sandblasted from the inside. Proper design will also help avoid oversizing the laterals as it goes down the line. At 130 GPM total, the potential cost saving of proper lateral sizing can be significant.

The system you're talking about should be engineered stem to stern. Take the time to do the math. For most typical residential systems, there's a lot of slop in the rule of thumb sizing everyone uses and plenty of room to have it all just work out in the end. In contrast, at around 130 GPM per zone, all the stuff everyone wants to ignore will be a factor. At those flow rates, ignore friction and velocity at your peril.


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## hsvtoolfool (Jul 23, 2018)

I agree 110% with @Delmarva Keith that you must do the math and verify that you won't have severe water hammer. Dems some big pipes and flow rates! You're definitely into the golf-course-pro-equipment realm with your GPM and pressure specs. Match the head inlet size to a rigid "swivel" swing joint riser. If the head has a 1" inlet, then use a 1" rigid swing joint.


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