Mexstan

Need some advice / suggestions on how to fix a sprinkler problem that I have. First, some history. Some time ago I added a few heads which slightly reduced the throw for all the heads. Now the 20 year old pump died, so being the brainiac that I am, figured that in the process of installing a new pump, would upgrade from the old 3/4 hp to a 1 hp to compensate for the added heads. The pump I installed is the same brand, shape and appearance as the old pump. Did not check the pressure rating. It was almost a drop in, except that this motor is physically larger, so needed to redo the connections because the intake is now about 1/2” higher than the old pump.

Here is the problem; when the pump comes on, now all 4 stations come on at the same time, but at a very reduced throw. I figured that in the process of changing the pump, had somehow introduced some debris into the system which was holding the valves open. Dismantled every valve, but no debris. Then guessed that maybe the controller had died too, so disconnected all 4 valves (Rainbird) at the controller. Same problem as all the stations still open when the pump comes on. Is it possible that the new pump is overpowering the closed valves and forcing them partially open? I asked this question at the local Rainbird dealer, but they tell me that their valves should hold the pressure. I still question this.

So now what? Go back to a ¾ hp pump? Get a different pump? Install a pressure gauge and an expensive pressure reducer?

ssandlin

During your rework of the system is it possible that the controller lost it's setting that specifies one station at a time and for how long each station is to run? Easy enough to check if you have not done that.

Mexstan

Good thought, but that is not the case. It shows all 4 stations and cycles through them even though they are all working together. In any case, I bypassed the controller by disconnecting the valve wires. With no power going to the valves, they still all open.

SIXSLUG

You're gonna have to dig up all the plants and move em closer to the sprinklers....I had this happen already.

Seriously though, can you put a gate valve in and just make 2 or 3 separate sections?

j_martin

All pumps are not created equal. If you replaced a 3/4 hp centrifugal pump (designed for irrigation) with a 1 hp jet pump, (designed for higher pressure), you'll get less water delivery. I suspect that is what you did.

Mexstan

After playing with this for hours, finally got it figured out and working.

I was suspicious of the new pump having a higher pressure than the old, so this afternoon figured out a way to measure the pressure of the old pump and the new. The new pump is 2 psi higher than the old pump, which is nothing. After much fiddling and head scratching the penny dropped and everything is now working hunky dory. The problem; changing the pump induced air into the valves. There is a bleed screw on top of each diaphragm and once I bled the air out, hallelujah, everything worked properly. Figured the trapped air on top of the diaphragm did not allow proper pressure equalization from one side of the diaphragm to the other. On looking at the valve design, it is easy to see that air on top of the diaphragm would allow the incoming water pressure to easily lift the valve seat, even if the valve is closed.