A Word on Water

Irrigation Management - A Stuck Valve? What Is It? And So What?

  

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Stuck valve.  To most people this likely brings to mind some kind of medical condition or perhaps a home repair.  Well, to those who deal with irrigation systems, both residential and commercial, it is a well known but not an everyday event. 

It is a valve that is allowing water to flow through it and move downstream to sprinkler heads.  In effect the valve is "on" even though it is not being charged electrically by the irrigation controller, which is the only way that the valve should be letting water through.

The most common reason that the water is flowing in this manner is because of debris lodged inside of the valve which prevents it from closing.  Hence, it is called a stuck valve.

Another reason a valve stays stuck is due to a hole, even a very small one, in the diaphram.  This piece of the valve is what actually seals closed the water port inside the valve when it is not charged by the irrigation controller.  A hole in the diaphram compromises this design and allows water flow to continue.

Whatever the cause of the stuck valve, the result is the same: wasted water.  No matter how well or how poorly an irrigation controller is scheduled, the irrigation program is set based on the goal of watering the landscape enough but not too much.  Should a valve not close when it is no longer charged by the irrigation schedule and remain stuck open, water is being applied to that part of the landscape beyond what is programmed.  Wasted water.

How much water is wasted depends on a couple of factors.  One factor is how many sprinkler heads are supplied by the problem valve.  More sprinkler heads means more water.

Another factor is the master valve.  The master valve is also wired to the irrigation controller and all of the water run by that controller flows through it and goes downstream to the valves that supply the sprinkler zones.  Any water that reaches grass, shrubs and flowers goes through that master valve first. 

Is it a normally open or normally closed master valve?  A normally open master valve remains open all of the time unless it is electrically charged by the controller, which will close the master valve.  In this case, a stuck valve will run non-stop until its water supply is closed at the master valve or when the offending valve is corrected. 

The fact that a stuck valve will run continuously with a normally open master valve is bad and good.  Water is wasted without interruption, but given that it is more likely to be seen at some point because it will be visible during the day.  Irrigation schedules typically run at night, which is when stuck valves first surface.

A normally closed master valve only opens when it is charged by the controller.  In this case, a stuck valve will run only when the master valve is open, which corresponds with when it is running an irrigation schedule.  If no irrigation program is running, no water is flowing through the master valve or the stuck valve.

This type of master valve means less water is wasted from a stuck valve, but when will the problem be identified?  Since irrigation programs function at night, the stuck valve will only be visible at night too.  No one is around watching water run at night, so it could be weeks or months before anyone becomes aware of the problem.

The best tool to at least identify the presence of a stuck valve is a flow sensor.  A flow sensor becomes the eyes to measure too much water is flowing at night.  However, a flow sensor is not enough.  It can see, but it cannot do.  We will address the do part in another post.