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New Member

Posts: 6

Location: Leesburg, VA


Saturday, June 13th 2009, 8:14pm

Nelson I20-ADS arc - this is tough (for me)

Hi folks,

About two years ago, I installed a sprinkler system comprising of Nelson I20-ADS rotors. Everything works, I have adequate pressure and volume but the arc on these rotors is terrible. Here's the scenario:

On the Nelson rotors, 75% of the water is in 20% of the arc. So, in a 25 foot throw, about 5-10 feet get soaked while the other 10-15 feet is relatively dry. Last year I bought from 7-20 foot nozzles to no avail--they just simply lowered the arc but didn't change the water distribution.

I was surfing the web and ran across Rainbird's advertisement and captured the following image... this describes my problem exactly! I just don't know what to do next other than pull these things out of the ground.

Any recommendations?

Thanks, Jason


Supreme Member

Posts: 5,331

Location: Metro NYC


Sunday, June 14th 2009, 2:24am

Modern nozzles don't give horribly uneven coverage unless your pressure is too low, so it comes down to user error. Re-nozzling a size smaller can help - pressure at the heads goes up, and distribution improves. Try setting out some catch cans to measure the water being applied.

The photo you linked is an example of the sort of "beauty contest" that's happening these days, that doesn't have all that much to do with good coverage. You aren't supposed to see much water landing a foot from the head, since the area covered is one-thirtieth of the area covered at thirty feet from the head.

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