# Low Pressure on One Zone



## jfridge92 (Apr 10, 2021)

Hi all,

I have a Hunter irrigation system at the house we bought in November of 2020. The system I am assuming was put in when the house was built in 2017. It's a 5-zone system with a Hunter Xcore controller, and Hunter PGV control valves (the older style, not newer style). I unfortunately didn't catch this for about 2 weeks since the sprinklers run at 3-6am, and only noticed when the back yard started dying.

I am having an issue with a zone that previously worked and no longer does, Zone 5. When the zone kicks on from the controller, none of the 8 rotors pop up, but I do see water pool at the top of each rotor in the yard, so the valve is flowing, just extremely low pressure. All of the other 4 zones work with perfect pressure, so I know this is not a supply issue. There is only one main turn on valve for all 5 zones, and it is fully open.

When I open the bleed valve on the Zone 5 valve, all 8 sprinkler rotors pop up with full pressure like normal, so I'd think this would rule out a leak or blockage downstream of the valve. ​One thing that is odd is that when the bleed valve is open and the sprinklers are on just fine, the valve is quiet and flows. When the controller commands then valve to open, it squeals loudly at the valve, and I can hear and feel the irrigation lines below the ground banging and vibrating. 
There are no visible leaks at the valve or in the valve box, however I did notice when the water is off, if I remove the zone 5 solenoid, a lot of water will still come out of the solenoid port. If i remove the zone 4 solenoid, water barely trickles out of the solenoid port.

So far, here's what I have tried to troubleshoot: 
- Replaced the Zone 5 solenoid with no luck
- Confirmed I am getting 26v from the zone 5 terminal at the Xcore and at the valve's wiring
- Confirmed that the new solenoid does retract the plunger when commanded (verified this by turning on that zone while the solenoid was wired in the valve box, just not installed in the valve itself). 
- disassembled the top of the valve, cleaned the exhaust ports and bleed ports, did not notice any tears in the diaphragm
- swapped Solenoid from Zone 4 to Zone 5 (I kept the solenoids wired to their original zones and commanded zone 4 on in this case) and vis versa - Zone 4 functions correctly using the zone 5 solenoid, zone 5 does not function with the solenoid that's wired to zone 4, same symptoms as listed above.

The only thing I have not done yet is replace the entire top of the PGV valve on zone 5 with a new diaphragm and lid. Before I throw any more parts at this thing, does the diaphragm sound like the likely culprit?

Thanks in advance!


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## g-man (Jun 15, 2017)

Swap the internals to see if the problem moves.


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## jfridge92 (Apr 10, 2021)

Thanks G-Man! Swapped zone 4 and 5 guts and that did the trick. I replaced zone 5's top with a PGV-1 top and it works flawlessly, although I now need to adjust all the rotors in the back yard because I'm getting a lot more pressure than before. Glad this problem is fixed, hopefully in time before I have to re sod the entire back yard Hah!


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