Sprinklers go on, then off, then on again

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Stan Robertson

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Hello all. I am hoping you may be able to help me with an issue I'm having. I have a 6 zone system that draws water from the lake behind my house. When I start the system up, starting with any zone, the system starts, runs for about a minute (or less), then the pump runs dry so the sprinklers stop pumping water. However the pump does not go off so it continues to run until it's pulling water again (for maybe another minute) and automatically switches to the next zone (since the previous zone went off). I am wondering why it it running dry for that minute. I thought if the check valve were bad it would run dry from the start. I have a brass check valve out by the lake that I changed about 2 years ago (I replaced a PVC one with the brass).

The intake side of the pump does not appear to be leaking at all or drawing air. Is it possible that the check valve might have a small piece of something in it keeping it from closing completely? Should I check to see if there is a clog from where the water is actually drawing from. The end of the pipe has a big diffuser (I think it's called) with a big screen on the end and a number of small circular screens on the sides. I changed that about two years ago also.

I'll add that once the sprinklers are running everything works fine. The 15 minutes off between zones doesn't seem to affect anything. It just when it starts after a couple of days of being off that I experience the problem. Thanks in advance for your help.
 

WorthFlorida

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Your second paragraph is all correct. You are losing prime and it is probably the check valve. It may have a stone or a piece of sea shell stuck in it or somewhere between the pump and the check valve is a small crack or break. Air is being drawn into the suction pipe when off but not all of the water is draining back. The one minute of water is what's in the pipe.
 

Stan Robertson

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Thanks very much for your reply. I was hoping you'd say I was wrong :) I was just surprised all the water was not draining back. I thought that would be a given if the check valve were bad.

So would you suggest pulling the check valve first? Is there a way to determine if it is bad or should I just replace it and hope for the best? Thanks again I really appreciate you taking the time to answer my post.
 

WorthFlorida

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I would replace the brass check valve with a plastic one. At my church where I worked I had to replace a brass check valve for the spring had broke. I spent $180 on a three inch brass unit and not soon afterwards it was losing prime again "at times". After a few years an irrigation tech replaced all the fittings with PVC and a PVC check valve. Works like a charm now. The brass check valve spring was still good but the water was working pass the plate inside of it. But you might just want to pull the brass valve out and look for debris inside. It could be your pipe to the lake has a rise in it so water remains from the pump to the rise before going down into the lake.
 

Stan Robertson

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It's interesting that you say that. I changed the PVC valve to brass because I heard that was better. It was like $40 vs $12 for the PVC valve. I will do as you suggested and take the valve out and inspect for debris. Maybe I'll just be able to flush it out. As for there being a rise in the pipe to the lake I have no idea. It's about 150' from the pump to the lake so who knows what that underground pipe looks like. Just when my last check valve went it was losing prime straight from the start, but that valve was stuck in the open position with a decent sized piece of shell. My diffuser screens had holes in them and there were actually two crawfish living in it lol. I don't think that helped matters any. I'll take it apart over the weekend and report back with my results. Perhaps my experience will help someone else down the line. Thanks again for taking the time to respond - much appreciated!
 

Stan Robertson

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Hi. Just wanted to give an update. It must have been the check valve that was the problem. I changed it over the weekend and my problem is resolved. When I removed the old check valve it was not filled with any amount of debris and the spring seemed to be in good shape. However since my problem is resolved it must have been the check valve. Guess the only way to know for sure is by changing it because I visual inspection really gave me no clues that there was a problem.

I also changed a coupling that was a bit loose, but since that was beyond the check valve (between the check valve and the lake) I doubt that was causing any of the problem. Cleaned out the screens on the diffuser too. Should be good for a while I hope thanks for all the help.
 
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