Why intermittent low pressure in one zone only?

16 years ago

Hello,

We've been experiencing a perplexing problem with our front yard irrigation system that had previously worked perfectly for 15+ years. Four irrigation zones operate normally, but the zone that waters the large lawn area has a problem with inconsistent pressure that began this Spring.

I've had an irrigation repairman out twice, but of course, the zone works perfectly when he is here (turned on at the valve or at the control box) - all pop-ups pop up with good water pressure. At my insistence, he replaced the valve for that zone and also replaced some of the sprinkler heads, but the problem remains.

When I turn the zone on through the control box, either manually or through the timer, 70% of the time there is inadequate pressure to bring all the sprinkler heads up fully - water streams from the bottom of each sprinkler head. There is no other water usage at the house during these times to account for the drop in pressure. I've tried testing the zone at different times of the day, early morning, middle of the day, late at night - doesn't make a difference, sometimes they will work, sometimes not.

I've checked for soggy areas but can't find any.

Does anyone have any other ideas what the cause for intermittent low pressure on one zone?

Thank you!

Linda

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Comments (11)

eddywill64
16 years ago
Linda I have a very similar problem and no answer. For me its Zone 2 it will start run for a few minutes then lose pressure - just about shut down all heads then surge back to full pressure. a little while later it will drop out all the way till the heads disappear. It does not happen when I manually run another zone.... I have replaced the valve (I even took and old diagram out cut the entire center out and it still "surged") I have no idea what it is BUT when I run another zone at the same time it does not happen I am lost but working on it!
anotherlinda
Original Author
16 years ago
Hi eddywill64,

Thanks for your reply. I think we must have gremlins!

If you do figure out the cause for the pressure drop, please post it here. I'll do the same.

Good luck!

Linda
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eddywill64
16 years ago
Linda I am on another forum and I have had some additional questions but nothing yet! are you on a pump or municipal supplied water? Eddy
anotherlinda
Original Author
16 years ago
Hi Eddy - We are on municipal water.
eddywill64
16 years ago
Good Morning Linda so far the consensus is that I have a "porting problem" I will keep you posted. When you operate your weak zone can you manually open another zone and see if the weak zone kicks in better? That is what is helping them diagnose my issues. Eddy
anotherlinda
Original Author
16 years ago
Eddy,

I'm trying to see what happens when two zones are operating at the same time, but can't figure out how to do that. I can start only one zone at a time from the timer/control box.

The new valve the repairman installed has an "On/Off" lever, so I can start that one at the valve, but the other valves only have a type of screw lever at the top of each - I've turned them but nothing happens.

In the next few days I'm going to randomly turn the lawn zone on through the valve lever (not the control box) to see if the pressure varies when started that way. This morning it was very strong and worked perfectly.

I am going to google "porting problem" - though I'm not mechanically minded, it sounds interesting :o)

Thanks for your help!
Linda

The new valve has an easy "on/off" lever.
ronalawn82
16 years ago
another linda & eddywill64, I do believe that you have a 'porting' problem. Here is what I think is happening. The valve opens when the water in the top chamber is led away. This happens when the solenoid opens a port, and the water flows out. This is helped along by a spring pushing on a flexible diaphragm. Visualise a piece of debris in this top chamber finding its way to block the port. The chamber fills up with water and the valve shuts down. The piece of debris sinks and the port is opened once more and the cycle repeats. This would explain the surging BUT I cannot explain how the simultaneous operation of another zone resolves the problem. And sorry, I am too science-minded to believe in gremlins; although I will not walk under a ladder!
anotherlinda
Original Author
16 years ago
ronalawn82,

Thanks so much for your reply.

I'll call a different irrigation repair company and have them check for a porting problem.

I'm very grateful for your and Eddy's advice. Love these boards and the kind folks on them.

Linda
eddywill64
16 years ago
My issue is not resolved yet I am going to replace the whole valve on my zone (i replaced the top half earlier) I will let you know when and if I figure this out!
eddywill64
16 years ago
replaced the whole valve and I checked the intake side check valves for debris and they are all good - still the same problem next trick is to re-plumb all the control valves I will keep you posted - I know this doesn't help you yet but if I make a land mark find then who knows! Eddy
anotherlinda
Original Author
16 years ago
Eddy,

Thanks so much for keeping me posted - I really appreciate hearing what you are doing. I'm keeping my fingers crossed for you!