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Thursday, April 5th 2012, 6:20pm

Control Valves

I've been dealing with irrigation systems one way or another for 40 years; installed several, repaired dozens of problems, etc . But one thing I've long puzzled over and can't get into my head (even though I've opened up and cleaned several of them) is the exact internal mechanics of the typical solenoid control valve. IS THERE, somewhere, a set of diagrams of the interior workings of the typical small commercial / residential type - (i.e. Rainbird DV series, Weathermatic 21000 or 8200 series, etc.) control valve showing the water flow path in the open and closed positions, how the solenoid's action effects the opening and closing, etc. ???
Thanks for any help you can offer.


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Posts: 42

Location: east coast


Thursday, April 5th 2012, 10:00pm

valve operation

Many irrigation manuals and books have chapters on valve operation. Weathermatic's Turf Irrigation Manual is a good source for information on valve operation especially their reverse flow type of valve. You could also check with the National Irrigation Association website and check through their library of books etc. The basic principals of valve operation are the same for most all valves. The bottom of the valve , where the source water is, is separated from the upper chamber by a rubber diaphragm. When the valve is in a closed position there is water in both the upper and lower chambers. The reason the valve stays closed is because the water exposed surface area on the upper part of the diaphragm is larger than the water exposed surface area on the lower part of the diaphragm. Therefore, there is more force acting on the upper part of the diaphragm which keeps it closed. When the controller sends a signal to open the valve the solenoid plunger is lifted up which exposes a water exhaust port which sends the water in the upper chamber to the downstream outlet of the valve. When this happens, you lose the hydraulic advantage in the upper chamber because the water has someplace to go. The water at the bottom of the valve diaphragm pushes it open and the water now goes through the valve. Likewise , when the electric current is stopped to the solenoid, the plunger drops down, closing off the exhaust port. The pressure will then begin to build up again in the upper chamber and the diaphragm will slowly close as it reaches that hydraulic advantage again. If you want to understand through the use of a formula, use P(pressure) = F(force) / A(area). As you will see, at a given pressure if you change the area the force will change.


Friday, April 6th 2012, 8:10am

Go to for a decent Hunter video. Look on the bottom left for a PowerPoint illustration.

If you want to drift into the weird, irrigation valves are used in potato guns. There's an interesting video on Youtube at
You might have to cut/paste these links into your browser.


New Member


Friday, April 6th 2012, 10:59pm


Hey Pass1 and Gator Guy,
THANK YOU VERY, VERY MUCH for the info. You've resolved a years long nagging puzzle for me. The flow of information out there on the WWW these days is truly mind boggling.

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