# One Irrigation Zone Suddenly Has Very Low Pressure



## silvertonesx24 (Aug 15, 2020)

Heads: Hunter PGV


Voltage at Control Panel tests fine

OHMS at Control Panel tests fine

I feel water flowing through the valve at the valve box

Other zones in the valve box work properly

Opened the solenoid manually, no change

Opened the valve control on the unit, no change

5 sprinkler heads on the line. The head on the very end of the line comes up when the zone is running, but with very low pressure. Stomping the head does not raise other heads

Ideas before I have to call my pricey service guy?


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## g-man (Jun 15, 2017)

You likely have a leak after the valve. Let the zone run and then look for the water/mud spot.


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## RVAGuy (Jul 27, 2020)

+1


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## thebmrust (Jun 29, 2020)

What about an object in the line? I had a similar problem and couldn't figure it out. But after about two months a decent sized pebble finally moved from line to sprinkler. Remove sprinkler AGAIN, remove pebble, water flows normal now. (Only (3) 3/4" heads on that line).
Note: 
1 1/4" supply line @50psi
3/4" arterial
3/4" riser
3/4" brass impact sprinkler
Pebble was appx 3/8"x1/2"


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## silvertonesx24 (Aug 15, 2020)

So after doing some inspection, I found some more clues.

It is zone 2 that is not working, very low pressure. There are no visible water breaks I can find.

In zone 10 (shares a box with zone 2), there is a soggy spot by a downstream sprinkler, but nowhere near the zone 2 heads.

When zone 2 is on, zone 7 sprinklers partially come up. This baffles me because zone 7 is not only nowhere near zone 2, but it doesn't even share a valve box.


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## TSGarp007 (May 22, 2018)

Does zone 7 partially come up when any other zones are running other than 2?


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## RVAGuy (Jul 27, 2020)

The only thing that can cause zone 7 to partially come up when zone 2 comes up is a drop in water pressure. I would unhook a solenoid wire going to 7 just to be sure it's not electrical. These valves rely on water pressure to stay shut. If zone 2 has a huge leak, it will reduce pressure in the main and this may be enough to make zone 7 leak.

I would also pull the top of the valve on zone 7 to make sure you don't have any debris that could make a leak if the pressure is reduced. Something small like sand between the diaphragm and the diaphragm seat.

I'm not too concerned with the wet spot around zone 10 because that is after the valve and is "independent" of zone 2. I would just verify there is no water flowing there when zone 10 is off. Open the box and listen to/feel the valve to try to detect any major water flow. It could just be a low head on that zone and the check-valve in the spray body isn't functioning properly (if you have check valves in your spray bodies).


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## silvertonesx24 (Aug 15, 2020)

So I did some tests

Zones 1, 2, 3, and 9 share a valve box.

If I disconnect Zone 2 solenoid, I can manually activate it and hear rushing of water into the valve. I assume this means the valve works OK.

With Zone 2 valve open, I can manually open Zones 1, 3, and 9 and that will cause sprinkler heads on each respective zone to rise.

If only Zone 2 valve is open, I get only a little water at the sprinkler at the very end of Zone 2. However, either Zone 10 or Zone 7 (from a completely different valve box) may partially be spraying while Zone 2 is open. I assume this is the case, because the water has to go somewhere.

There are no leaks or soggy spots at all.

The Zone 2 line does have one point halfway down the line I can hear burbling water underground. However, no wet spots and dry, dead grass all around it.

Is it possible I have a partial clog somewhere in the line, (possibly where I hear the burbling) and this is causing very low pressure, and forcing other zones up?


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## silvertonesx24 (Aug 15, 2020)

Also when I checked the 3rd irrigation box after running zone 2 (Zones 6, 7, and 10), it had a bit of water in it. So I assume I have at least some valve problem there.

I feel like I'm playing real life Myst.


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## RVAGuy (Jul 27, 2020)

If there were a blockage, this would cause low pressure downstream of the restriction. The rest of the main would still be close to system pressure and the zone valves would remain shut. But you are 100% on to something. Investigate it. You shouldn't hear gurgling along your sprinkler lines.


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## silvertonesx24 (Aug 15, 2020)

So I fixed leaking Zone 7 and 9 by replacing the valve components, no more leaks and good pressure on other zones. But...still the same on Zone 2.

I'm thinking maybe I have a partial block early on in the line and I only get pressure enough at the end of the line to raise the sprinkler?

I don't see any other leaks on the system, the water has to be pumping somewhere though.


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