Question
Hi Jim, my irrigation pump is supplied from a tank (0 to 2 metres above the pump) and a pond (1.5 metres below the pump. These two separate sources are controlled by solenoid valves - one for the tank supply and one for the pond. These are fitted before the pump suction inlet.

If I want water from the pond the tank solenoid is off (or vice versa for water from tank).

Issue is when drawing from the pond the tank valve, although closed, does not stop the water flow. I've checked this by physically turning off a manual valve on the tank. I think I have the wrong types of solenoid valves - 2 way simple irrigation system valves. It appears they don't stop water when under suction pressure as opposed to pressure at the inlet.

What valve could I use on the water line from the tank so it would automatically close and not let water through when I am using the pond?

Thanks

Answer
Hey Mreight, I hope this helps. Any solenoid valve will require at least 15psi behind the valve, for it to close properly. If the tank is elevated, I would suggest that you pipe from the tank down to the ground, and then install the valve, this way you can create more pressure behind the valve. The higher the water feeding the valve, the more pressure it will create. Rainbird produces a automatic valve (solenoid valve) model #DVF series that operates from 15psi to 150psi. I would suggest using this valve since it will operate at 15psi. Let me know if I can be of anymore help, thanks and good day mate.