Plug the heads and leave it on, and the wet spots should show up

Thanks for your help. Since my knowledge of sprinkler is very basic, I have other questions.

1. How to plug the heads?

2. what is the hub? How can I know which one is leaking?

3. I think at least I need to find in which zone the leak is. How can I do that?

Thanks

Julie how do you know it is your sprinklers that is leaking?

You can plug the heads by removing the sprinkler first, putting in a riser and capping it off with a screw on cap. You can get all the materials in either Home Depot , Lowes, Ace, ...

Finding out which zone the leak is in
1. Turn on the water to the sprinkler system, keep the system off and see if the indicator moves. If it does, probably it will be close to the main supply line, after the shutoff valve. From the description of your problem, this is the most likely problem. Possible issues - cracked pipe or bad control valve (any dribbling water?).

If there is no leak,
2. Plug all the sprinkler heads/hubs.
3. Turn on individual zones one at a time. See if the indicator moves when each individual zone comes on.
4. It would be a matter of digging up the pipes and figuring out which cracked.

Don't know your irrigation system or water usage, or cost of the waste but.....

If your system leak is a real water-gobbler and other detection methods don't work for you, there are folks who offer detection services for sub-surface leaks. Essentially they connect compressed air to your system and use a sonic sensor placed on the ground to find the place by listening. Works quickly and well. Bad news is the typical charge is around $300.00. I don't know if you have a three hundred dollar problem.

Thanks, David and asolo.

I will call the city to unlock the water meter lid and see if the leak indicator still turns when no water is used.

David, do you known usually how long the main supply line is? My water meter and the main valve of sprinkler are close and just across the side walk. Water meter is at the outer side. The main valve of sprinkler is at the inner side. I do not have the layout map of the pipes.

That's a difficult question to answer as it depends on the layout of the plumbing system.

The little red indicator will not turn if no water (fluid) is used. It would be difficult substituting a different fluid (eg - gas or liquid) from the meter and could cause other issues.

Start the process by first looking at the control valves.

You may find the following site useful

Here is a link that might be useful: irrigation tutorials