Question
QUESTION: Our sprinkler system suddenly stopped working. We have a 4-zone sprinkler system with a Toro controller. The controller tells me that the zones should be running but none of the heads are watering. But the backflow preventer is leaking out of a circular box at the top (I don't know what that component is called - it has a lid held down by 2 screws. I opened the lid and there is a white piece inside and a spring). The leak is more than just dripping but it is not gushing. It leaks whenever I turn on any zone, either automatically or manually, but not otherwise.

The system was working until a few days back. The only things that have changed recently are:
1. There was a wooden plank covering the backflow preventer until a few days back. The temperature has been in the 90s the last several days and now the backflow preventer is exposed to direct sun for a few hours a day. Could the heat have broken something in it?
2. I am working on one of the sprinkler heads to convert it to drip irrigation for a raised bed. But this zone has been shut off for the whole summer (because of other work that has been going on there) and I haven't turned it on yet (except to check the system today)
3. I recently mowed and edged the lawn, but as far as I can tell no wires have been damaged.

The fact that water is leaking from the backflow preventer when I turn on the sprinkler system (and only when I turn it on) tells me that it the system is trying to run, but something is preventing the water from getting to the sprinkler heads and instead the water is leaking out of the backflow preventer.

I am hoping this is something I can fix myself without having to spend a lot of money on a professional. I am inexperienced with irrigation systems, but am fairly handy when it comes to using tools, etc.

ANSWER: Thank you for complete information. It's almost as if I were there looking at it.
Commonly, the backflow preventor will dump water out of the top when it is lacking water. This would go along with your problem of leaking only when you turn on a zone. For some reason the water supply has changed. First check the valves before and after the backflow. They should be ball valves. Make sure they are all the way open. Then, check the supply valve which feed the backflow preventor(inside the house). Turn it on and off a few times. Sometimes the closing parts of manual valves do become loose and won't open all the way.
Next, would be to remove the cap of the backflow and remove the inner parts. (Attached is a link to the type of backflow I "think" you have.) Then try turning on the water. If you get good flow then you know the water supply to the backflow is good.
At this point, if nothing has helped reply back with results. I'll try to direct you to the next move. If you can find a model # of the BF it would help.

Matt

http://www.watts.com/pdf/es-800m4qt.pdf


---------- FOLLOW-UP ----------

QUESTION: Thank you for the prompt response. The model is the same as the one you emailed (800M4QT 1" - 2").
1. I've turned the inlet and outlet shutoff valves on and off but that didn't fix the problem.
2. I could not locate the supply valve - there is nothing inside the house that seems to control water to the BF. Could it be buried underground as the PDF seems to indicate?
3. I removed the hood, bonnet and the vent float and turned on the sprinkler. The water flow did not appear to be "good" - meaning, I can't imagine any of the sprinklers operating with that kind of a flow.

I did some more reading online and I think I understand how this BF preventer works and what the problem might be. The BFP I have needs at least 1.5psi pressure in the inlet to push the vent float up so water can flow to the outlet. Based on what I saw when I opened up the hood and turned the sprinkler on, I don't think there is enough pressure in the inlet.

But I can't think of why the pressure would drop all of a sudden within the last few days. I see no other visible signs that would indicate a leak - the pressure in other faucets in the house (interior and exterior) appears to be fine.

Here are some pictures of the BFP.
http://picasaweb.google.com/vinod.public/BackflowPreventer

The last one shows the water leaking when the sprinkler is turned on. Behind the BFP is the garage where there is no supply valve as far as I can see. The wire from the controller (which is in the garage) enters the ground about 10ft from the BFP around the corner of the wall.

I hope this is still within the limits of what I can fix myself! At the very least I've learned a little more about my irrigation system now. Thanks once again for your help!

Answer
I wish all the questions were as complete as yours.
That sure looks like a restricted supply in the picture of it running water. By the description, I'm sure it is.
Have you found your water meter? Or. If you have a well, the pressure tank? This would be the location for the supply valve. That valve, I believe is the key. It may be necessary to dig-up the pipes at the base of the BFP to get a direction to the supply. It could be 10'-20'from the BF before it enters the house. Are you in a freezing climate? That would help me direct you better.
You mention "other work" being done around the yard. Was any of this work near the backflow or the foundation of the house? Might be a place to look for a kinked line.
Let me know how I can help.

Matt