I would like to buy a pressure activated water valve (for irrigation), so that when the water pressure is above P1, the valve will turn on, and when water pressure drops below P2, the valve will shut off. Does anybody know any product that would serve this purpose? Thank you.

  • I don't think it can be done without external power. There wouldn't be enough energy to stop the flow once it started. So it must be some electrical means involving pressure switches and solenoid valves. – Dan D. Jul 14 '18 at 21:48
  • Try this products.danfoss.com/productrange/refrigeration/water-valves/… I know that is refrigeration - you might be able to use for irrigation - but hey if they make them for refrigeration - I am sure you can ask about irrigation. There are electronic systems available - if you are looking for that - write back and state that electric is fine, Industrial systems use them all the time.. – Ken Jul 14 '18 at 22:44
  • For irrigation, why do you need two set points instead of one? Also, is P2 higher or lower than P1? – fixer1234 Jul 14 '18 at 23:14
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    @DanD. This can trivially be shown to be false. A spring loaded check valve will open at a pressure greater than opening pressure, and close at a pressure less than closing value. The spring stores the needed energy. – vidarlo Jul 15 '18 at 8:51

What you are looking for is generally called a Spring loaded Check Valve. A spring presses against a ball which seals the line. Flow only occurs when the pressure can overcome the force of the spring. But that only gives you a single pressure to work with.

See Check Valve for an overview

  • Once the pressure has overcome the spring, how will the valve then close? – Solar Mike May 15 '19 at 17:08
  • @Peter M Check valves are used for preventing water from flowing backwards when the water pressure drops to low. ( such as in line between a well and a pressure tank ) Normal water pressure pushes against the valve and spring opening the valve, if the water pressure drop to low the spring pushes back and close's the valve so water dose not get pushed back towards the supply side. – Alaska Man May 15 '19 at 18:15

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