Irrigation System Problems

[whitpet]

Hi - I'm looking for some advice, troubleshooting an irrigation pump problem. I've got an irrigation system using a jet pump on a shallow well. The system has 4 zones, 2 using spray nozzles and 2 using rotary heads. The system is about 7 years old and have worked fine with no significant issues. I have just replaced the pressure switch on the pump. The old switch began sticking, and would occasionally not cut off unless I tapped on it. The new switch is an identical 30/50 model, per pump specifications. The pressure regulator tank is set to 28 psi, per pump specs. Tank pressure was measured after killing power to the pump while the system was running, and then allowing it to drain off any internal pump pressure before the measurement.

After installing the new switch, the pump works fine on 3 zones. On one of the rotary zones, the pumps cycles on and off every 10-15 seconds during the irrigation cycle. When the system is turned off, the pump shuts down properly, with no further cycling. The pump does not have a pressure gauge, so I cannot monitor that. This never happened with the old switch. I'm at a loss what has changed or what to do next. Any suggestions are very much appreciated.
Thanks,
Whit

[Bob NH]

Trying to set up a pump without a pressure gauge is like a blind man trying to drive, or like trying to find a problem in an electrical system without a meter.

How big is your tank and how many GPM is your pump? What is the time to fill the tank (start to stop) with no usage?

The short cycling suggests that you have a problem with the air tank or the pressure switch settings. Symptoms are as if the zone is connected somewhere different or that there is a check valve somewhere. The pump should have reasonable cycles with NO zones on, and adding a zone should not "short cycle" it.

Procedures to use:
1. Buy and install a gauge near the tank and pressure switch (They are close together, I hope.)
2. Verify that the pressure gauge and the tire gauge that you are using to check air in the tank are reading the same, or nearly so. Do that by measuring air pressure when you have a gauge reading on the water gauge with some water in the tank. They should be the same.
3. Verify that your pressure switch line is not clogged with rust or dirt.
4. Verify that your pressure switch is not connected to a small tee that carries water to the last sprinkler zone. The pressure switch and gauge should be measuring tank pressure; not pressure in a high velocity line.

Fix the cycling problem before you ruin your pump and another pressure switch.

[whitpet]

Bob -

Thanks for your feedback. I installed a pressure gauge on the pump and discovered the 30/50 switch was cutting off at 42 psi. I didn't realize the switch was adjustable. After I found that info, I was able to raise cutoff pressure to 50 psi, and everything is rosy. As you recommended, I checked tank pressure vs. pump pressure with the system pressurized. They're reading within 1# of each other. When originally purchased, the pressure switch was connected directly to an outlet on the pump. I didn't change any of that, just swapped out the switch. Thanks for your help. Life is good....