Pump Start Relay question

[Yar02169]

Thanks in advance-
I have a regular, simple system for irrigation only. I have a long standing issue with some silt, and my work around is a filter after the pump, before the zone solenoids and sprinkler heads. For reasons unknown, sometimes when the irrigation is done, the pump continues to run, not turning off via the pressure switch [runs at 36psi, switch set to 40 psi]. I've also had issues occasionally with a pressure drop, in which case the pump turns on and runs, but doesn't build enough pressure to trip the switch (40 PSI).
To solve this, I bought a Pump Start Relay switch. I figure this will let my timer control the turning on/off of the pump, and let the rest of the system be. Now, if I do this, is there a need for the pressure switch and bladder tank, or can I remove them and maybe by a miracle also get the leak that allows the pressure switch to turn on the pump?
I would then have a check-valve, pump, pressure gauge, filter, sprinklers. I have seen it mentioned that a pressure relief may be required. If the system runs at 36 psi, what should the relief valve be set at? Why would I need it anyway, in case of the timer failing, or a zone solenoid failure, or a failed start relay? Unless it would be the last zone solenoid that fails, the pump would just continue to water my lawn, correct?
As I started, thanks in advance.

 

[Drick]

If you are using a pump start relay you will not need a pressure switch or tank. As you assumed you will need a pressure relief valve in the event a solenoid fails to open. I think your problem is going to be that you are operating your irrigation system at what appears to be your pump's maximum operating pressure. Your pump needs to be able to exceed that by some margin for your relief valve to operate properly as relief valves are generally not precision devices.

I'll use my system as an example; I use a start relay for my irrigation pump. My sprinklers need an operating pressure of 50 psi. My pump can produce a maximum pressure of 85 psi at zero gal/min. My relief valve is set to 70 psi. If a valve fails to open the pressure will reach the 70 psi limit of the relief valve and it will open and allow enough water to flow to keep the pump from overheating.

Also I'm not sure how your system is currently set up but your filter should be after the pressure tank and switch, not before it.

 

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[Valveman]

The stuff that you are filtering has worn down the pump. Probably won't be long before the sprinklers won't shoot far enough. You can use a pump start relay instead of a pressure switch/pressure tank as long as you don't use any faucets or hydrants. But a pressure switch is needed to have water come on when a hydrant is opened.

 

[Yar02169]

Thanks for the confirmation of my thoughts, that's what I like about this site.
Drick, my filter is last in line, before the zone solenoids. If I read your comment correctly, should the filter be before the pump? Mine is on the discharge side, not the intake. Just wondering...

 

[Valveman]

A screen is the best you can do on the suction side of the pump. A filter would be too much restriction on the suction, and so will a screen when it gets clogged. Just have to let the pump work with the dirt and filter it later.

 

[Drick]

The filter has to go after the pump and pressure switch/tank like you have it. I just wasn't sure about your setup.