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I am using well water. The static pressure measured with the outside faucet is 60 psi. When irrigation system is turned on, the water coming out of all sprinkler heads in any zone is weak. I guess the pressure at sprinkler heads is low. When irrigation system is on, water pressure inside the house is very low too and the PSI I read at outside faucet drops to 20 PSI. What could be the problem? Can low water in the well cause the problem?
Thank you!
It sounds like your well is not able to provide the flow rate needed to supply your sprinkler system.
Let's say that your well/pump/plumbing are able to provide 5 gal./minute. If you exceed that rate then the pressure will drop. It's unlikely that low water level in the well is the source of your problem as in that case the pump would start sucking air and you would notice the air in the system as it "burps" out.
I'd start by checking your plumbing for suitable sizes of pipes and fittings and see if there are any obvious problems such as way too small pipes. If that fails to reveal any issues you likely need to engage a well service professional who can evaluate your well and pump and make any recommendations that might correct your problem.
Keep in mind, especially if your well and pump are old, that fixing this may involve replacing the pump, drilling a new well, running a new pipe from the well to the home, etc. In other words, it may be expensive.
There could be several causes. Is this a new problem? Have you made any changes to the irrigation system? The most likely cause is you are simply using too much water than the pump can provide so the pressure drops until the delivery rate matches the consumption rate. Reducing the number of heads on a zone would address that issue. You may have to increase the number of zones to cover the same area. I assume you are only running one zone at a time, right?
It could also mean your well isn't producing enough water anymore, but the production rate of wells is usually pretty consistent. Still, the water level in your well might be dropping, making the pump work harder. And the pump could be wearing out. They don't last forever and maybe slowly failing.
One thing that has not been mentioned is what happened to me. I suppose through the minor vibrations caused by the pump turning on and off, over time, my main shutoff valve rotated itself into the off position. At first, pressure was dropping when more then one thing was using water in the house, eventually, no water at all.
When I went to turn the shutoff off, I noticed it was already off. So that is an easy thing to check before looking at other things. If it's a gate valve, also make sure it is fully open (and then back off half a turn to help prevent it seizing).
