Q.  I just restarted my sprinkler system after it had been winterized. When I turned on the water to the system, all the valves stations came on at once, as if by-passing the timer unit.  Even when I turn the timer unit Off, the sprinklers keep running.

A.   This is a common problem when restarting after your sprinkler system has been winterized, or after the system has been turned off for an extended period of time.  It also often occurs with brand new solenoid valves that have just been installed.  There are a  couple of possible problems that can cause this, so we’ll look at a couple of solutions.  One of the tricks below should get your irrigation valves opening and closing properly again.

Air Trapped in the Valve:

The valves may have air trapped in them.   A small bubble of air becomes trapped in the tiny water ports of the valve, this stops the water from flowing through the port.  Since the water flowing through the port is what holds the valve diaphragm closed, the valve stays open.

1. Turn on the main water supply.

2. Now go to the individual valves and using the manual open & close control on the valve.  The manual open & close control is either a lever on the valve (most often it is under the valve’s solenoid), or it may be a screw on the top of the valve bonnet.  If it is a screw don’t fully remove it, just open it until water starts squirting out.  Set it to open, wait a few seconds, then set back to closed.  If the valve doesn’t close within a minute, try it again.  It may take several tries to get the air bubble to “burp” itself out.  Try tapping the valve to dislodge the air while the valve is open if needed.  Note: old plastic valves may become brittle and crack when tapped, so if the valve is plastic and old don’t tap on it except as a last resort if the air doesn’t come out.

3. If that doesn’t fix the problem, you can almost always force the air out using the manual flow control on the valves.  Unfortunately, some inexpensive valves do not have a flow control.  The flow control is a handle, similar to what a manual valve has, that is on the top of the valve.  It works just like a regular faucet, turn clockwise to close.  Most flow controls have a hand operated flow control, others have a cross handle that is turned using a tool (pliers will work if you don’t have the special valve opening tool.)  A few valves have a screw for the flow control that requires a screwdriver to turn.  Try completely closing and then reopening the manual flow control on each valve.  That should force the air out and fix the problem.

Valve Needs to be Throttled:

If air in the valve doesn’t seem to be the problem it is possible that your valves don’t have enough pressure differential and they need to be throttled in order for them to close by themselves.

Here’s how to throttle them using the flow control adjustment:

Note: some inexpensive valves do not have a flow control adjustment feature on them.  If that is the case you are not going to be able to do this.  You will need to replace the valve with a better quality valve that has a flow control.

1. Use the manual flow control on each valve to close all of the valves.  Now the main water supply should be on, but none of the valves should be allowing water through.  So no sprinklers are running.
2. Start with just one valve at a time.  Rotate the manual on/off lever to the on position.  Open the manual flow control knob all the way (turn as far as it will go counterclockwise). The valve should come on and sprinklers run.
3.  Next rotate the manual on/off lever under the solenoid to the closed position.  The valve should close (it may take it a minute or two to close) but probably won’t, because that is the problem, they won’t close!   If the sprinklers turn off the valve is working correctly, go to the next valve and start again with step #2.  If the valve does not close by itself, you need to throttle the valve.  Continue to step #4.
4. To throttle the valve you partially close the flow control knob.  Start by turning it one full turn clockwise.  Wait a minute for the valve to close.  If it doesn’t close, turn the handle another half turn clockwise.  Wait again.  If the valve still doesn’t close turn it another half turn.  Keep doing this, at some point the valve should suddenly make a whooshing noise and close.  If the valve is broken it will never close by itself and eventually as you close the flow control more and more the sprinkler radius will start becoming noticeably reduced.  If that happens you need to repair or replace the valve.  But in most cases the valve will close by itself after you have partially closed the flow control.  It might take 4-5 complete turns before this happens.

You shouldn’t see any significant change in the sprinkler performance with the valve flow control in the partially closed position, except that the sprinklers may mist a little less (which is a good thing.)  This is called “throttling the valve” and some valves won’t close by themselves unless they are throttled.  The way a solenoid valve works is that the pressure differential as the water goes through the valve is what the valve uses to power itself into the closed position.  If there isn’t enough pressure differential the valve will not close by itself.   Often there is not enough pressure differential when there aren’t very many sprinklers on the valve circuit. When you throttle the flow control you are simply increasing the pressure diferential.

You can leave the flow control in a partially closed position permanently, it will not hurt the valve.  The valve is designed to allow you to do this.  The sprinklers should still operate well as the amount of water throttled when you partially close the valve is not significant.

For valve repair instructions see  how to fix a solenoid irrigation valve.