Dig up one of the spots and see.

That's probably what we will end up doing, The ground here is hard...rocky. It takes a pick ax to dig it up,so that will be the last resort. I was just wondering if anyone had any other ideas of what it could be. My husband is going to turn the sprinkler heads way down today & see if that makes a difference. It's weird, really.

See if you can get the water district to come out and test for chlorine. If there is chlorine its coming from the municipal water supply. If not its not coming from the sprinkler system.

Had similar situation at former home. An odd wet spot never did dry out but it was in a shady area so figured it was just slow drying after each rain. After a month or two and a high water bill or two I decided to cut off the water main from the street. With 10 minutes the puddle dried up (or soaked down). I dug down and at about 18" found that a rubber connector that attached 2 copper pipes together was rotted from an old defunct/disconnected outside hose spiget that was up against the house 5' away. I removed the rubber and just installed a cap on the live end pipe. Opened up the main valve and wa-la, no more leakage.
I'd suggest first cutting off the sprinkler main, if no sign of drying then cut off the house main if nearer the street. You say the soil is rocky, if no success on the 2 other sources then maybe a natual spring is nearing the surface?

Glad you found the solution to your problem. We shut off the sprinkler system 2 days ago. The spots are still there. They are wetter in the morning and sort of dry out during the day and reappear the next AM. So weird. We are in the desert so really don't think it's a spring. A few weeks ago my husband spread about 5 ton of small rock in the front..then this started. The rock in these wet looking areas feel oily to me..maybe it's something on the rock? Our water bill hasn't changed so don't think it's a water main leak. One of the neighbors said he has a wet looking area in his back. Ours is a lot of smaller ones and a couple big ones in the front.. This is puzzling.

Are you on city sewage or have a septic system?

We're on City sewage. There isn't any odor in the yard.

I live in the Arizona desert also and have gophers in my yard. this morning I noticed wet 3-4 round or oval shaped wet spots in my rock near a tree i have dug around and water every couple of days. could water be flowing through gopher holes and causing this problem?

We have the same problem and can't seem to find the cause. We had a 3-day rain a week ago, deep watered 3 small trees via drip system and now every morning have wet areas in the rock- some small and some real large. The valve is not leaking and we have turned off the timer but wet rocks continue to appear every morning. Ours too appear where there is no irrigation pipes. Still trying to solve the mystery. Any help outthere?

Was this figured out? We also have the same issue here in San Antonio, TX. Landscaper, pool guy and builder were all perplexed. I’m not very happy with this.

Start a new thread please. This one is 10 years old!

Im in So Cal and having the same problem. i have rock landscape and wet spots come out in the summer only. Yes kind of oily looking. weird? is it the rocks?

I just discovered the same issue in my new gravel pad. Did a web search and found that it is the Morning Dew for my issue.