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zhenya

Unregistered

1

Sunday, July 26th 2015, 4:23pm

Not getting enough pressure at sprinkler heads.

Apologies if I am posting this in a wrong section, but I desperately need help figuring our my sprinkler problem.

I have 1500 sq. ft. lawn broken in three zones. Each zone has 10 sprinkler heads all 12 ft. Most are 360 degrees, some (edges are 180 degrees). My GPM rate is 17GPM at water bib sitting right next to sprinkler valves and serviced by the same line. The water pressure is 160psi at the same water bib.

The lawn and new irrigation was put in about 10 months ago. With the heat of summer I started noticing brown/dry spots on the lawn. After lots of trial and error (re-piping valves, closing some sprinkler heads, etc.) I can see that I simply don't get enough water and/or pressure at my sprinkler heads.

The person that installed the irrigation and my gardener are both at a loss because they say that at 160psi there should be plenty of pressure for 10 sprinklers. Yet if I am truly only getting 17gpm and my heads are using 2.5gpm each it's not enough.

I unscrewed one of the sprinklers in put on a pressure gauge on the pipe. I am only getting about 25psi with 9 other sprinklers running.

Any help any advise would be appreciated. What am I calculating wrong? Could it be that 10 sprinklers are too many for 160psi pressure?

Wet_Boots

Supreme Member

Posts: 5,276

Location: Metro NYC

2

Monday, July 27th 2015, 1:40pm

Keep on the present tack. Cap off additional sprinklers, with a pressure reading after each one you cap off.

zhenya

New Member

3

Monday, July 27th 2015, 3:33pm

Wet_Boots, thanks for the reply. Do you find it normal that at 160psi I can't power 10 sprinklers?
my water line is 3/4 all the way from main and to each sprinkler.

Wet_Boots

Supreme Member

Posts: 5,276

Location: Metro NYC

4

Monday, July 27th 2015, 5:08pm

Pressure is only part of the story. Pipe layout is another. Don't expect to get 17 gpm through 3/4-inch pipe if the run is a long one.

zhenya

New Member

5

Monday, July 27th 2015, 6:54pm

I have three zones. all three are having the same issue. The run is about 50ft between my valves and the last sprinkler

Wet_Boots

Supreme Member

Posts: 5,276

Location: Metro NYC

6

Monday, July 27th 2015, 8:12pm

Look for a partially-closed valve somewhere in the supply chain.

zhenya

New Member

7

Monday, July 27th 2015, 10:24pm

Thanks. That's not it. The bib with 160psi is right where valves are. I just repiped just in case all the valves from the point where I know the pressure is. No change.

Wet_Boots

Supreme Member

Posts: 5,276

Location: Metro NYC

8

Tuesday, July 28th 2015, 1:48am

Pressure you measure when there is no water flowing has nothing to do with whether or not there may be some issue with a flow restriction in the chain of supply. You need to measure flow and pressure simultaneously in order to get an accurate picture. From your description of the situation, your "effective" flow capacity is well below 17 gpm

By the way, 160 psi is a damaging pressure, and higher than the rating of most sprinkler zone valves. Should you have a zone with too little flow, from clogged nozzles, for instance, the pressure in the sprinkler heads could exceed their ratings.

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