I have a shallow well sprinkler system with 5 zones.
The system worked fine when I bought my house 3 years
Ago but now the system barely generates enough
Pressure to cause water to come out of the sprinkler
Heads. The problem seemed to happen gradually. I first
Noticed low pressure in the zone with the most
Sprinkler heads but then noticed that the smaller
Zones were not working well either.

I bought an overhaul kit for my pump and rebuilt it
But the pressure remains low when I run the
Sprinklers.

I have a 3/4 HP Flotec FP4122-02 pump. The output of
The pump connects to a pressure tank. The pressure in
The tank is set to 28 psi (with the pump off and no
Water in the system). The cut-on switch of the pump is
Set to 30 psi and the cut-off switch to 50 psi. With
All of my zones off the pump will run until it reaches
50 psi and then shuts off. The pump does not run again
Until I open one of the sprinkler zones. Once a zone
Opens and pressure drops to 30 psi the pump comes on.
It then continues to run and the pressure remains
About 30 psi never going above that until I turn off
The sprinkler zone. There does not appear to be any
Air in the lines when the sprinklers are running, no
Spurting or air blasts. Once all zones are turned off
The pump then builds pressure back to 50 psi and turns
Off. So, the pump can build up pressure when no water
Is flowing out from the system but it seems that it
Can't keep up the pressure once water begins flowing
Out of the system.

I thought there might be a leak in the lines running
To my sprinkler heads so I unplugged my pump and
Hooked up a hose from my city water faucet to one of
My well water faucets and then activate my sprinkler
System (one zone at a time). All of the zones worked
Fine.

I've concluded that 1) my pressure tank is OK, 2) my
Pump is OK, and 3) my back-flow valve is working
Properly.


Where do I go from here in troubleshooting my problem?

If it appears to be a problem in my supply line going
Into the ground how does one go about checking it? The
Line goes into the ground under my house in my crawl
Space. I live in Chesapeake, VA which is about 7 feet
Above sea level.

Thanks for your help!

Rob

Just a guess, there may be some sort of mineral build up. I would remove the sprinkeler heads and soak them in some kind of "limeaway".

Since the sprinklers worked fine off city water, I would think that the problem would not be there. I would first check my pump capacity. Is there a fauct coming off the pressure tank that could be used for this? If so, hook up a hose and let it run wide open into a five gallon bucket. Use that to calculate about how many gallons a minute the pump is putting out. Check it several times over five minutes or so and see what you get. Sounds like the pump capacity is no longer up to taking care of several sprinkler zones at a time. Once you get the pump capacity (gals. Per minute at 40# pressure or whatever it is), you should be able to contact the manufacturer of the sprinkler system and see how many heads can be run with that capacity.