Water leak

Day one About 7am
I noticed a half moon shaped wet area on the soil along the outside of the garage foundation. About the size of a basketball. Also water is seeping along garage door. By afternoon it dried out.

Day two 7:00am
Wet area expanded. I dug a hole about one foot deep. no pipes found. By afternoon it dried out. Also water is seeping along garage door.

Day three
Checked area in the morning. Hole had 6" of standing water. Dried out by afternoon. Turned off valves to irrigation system.

Day four
Checked area at 1:30am. Hole looks empty. Checked area again at 5:30am and the hole had water in it again and water along the base of the garage door. Hole has 8" of standing water. Dried out again by afternoon. Called a plumber to come out and scratch his head for a hour $$$$$$.

Tonight I am going to turn off water main. The mystery is the timing. Why only early morning. The water meter is not registering any flow when all water is turned off inside.

I have no neighbors uphill from us.

Any thoughts?

Could it be the drains, so toilet flushes etc lead to a leak…

Its possible its water from elsewhere ?

Is there a road ? is the water being dumped into roadside drains , by some other neighbour ? and then ending up under your garage ?

Is there a neighbour uphill ? Does their sewerage pipe run down past your place to the road ?
Is that where the sewerage main runs ? Check your land title, council plans, is there a service who tells you where you can and cannot dig ? Or ask the water authority to fax the plan to you ? It might be the sewerage main backing up !.
There could be an old sewerage connection to the garage, it might have had sewerage/septic tank at some stage ? (is the septic tank under the garage ?)
But likely to be your household pipes blocked or broken.
Is there a septic tank ? Is there a dispersal pipe system after it ? This might be the outflow from the pipe that isn’t blocked… hence its coming out in a big rush.

Put a bottle of food dye into your toilet. Flush the toilet.
See if the water on the ground at the garage is coloured ?

map out your pipes including sewer/septic and irrigation. always good to know.

where the water seeps along garage door, place some dams (plastic bag weighted with sand) across the seepage patch periodically along its length. also strips of newspaper. see where the water starts and where it flows.

concrete garage slabs have lots of heat capacity. when it gets cool over night it holds that coolness for a long time. if your over nights and mornings are humid then water may condense on the slab and run down hill. unless this was extreme i don’t expect that it would generate a hole full of water.