Live in San Diego, CA in an early '70s townhome unit that shares both walls with a front courtyard. Previous owner rerouted the mainline from detached garage above ground (possible slab leak all of our pipes appear to be above ground now). We are digging a trench in our front courtyard to properly bury the main line before entering into the home above ground, plumber to install new piping. While digging the trench along the neighbors wall water started to fill in the trench. Followed the water to underneath the foundation into neighbors unit. Water fills the hole to a level then stops (stayed at same level overnight). Water is clear and cool. Have attached a photo. Called plumber to come out to evaluate. Townhomes are in a four unit block with same meter into city main (HOA fee includes water).
Plumber used listening device at pipe shut-off in garage for our neighbors and our unit, no sound of running water. Also listened interior of homes. Went to water meter at street (vault was full of water) and meter was not spinning nor were the numbers scrolling. Water still filling hole when emptied to same level. Checked irrigation lines, none in the courtyard or nearby. San Diego has received above average rain this winter and 1.5 inches last week. There is a creek runoff that is within 100 yards across the street and is about 15-20 feet lower in elevation that our home. There does appear to be water coming from the front lawn that slopes towards the street and into the gutter. Is it possible that the water table has risen? Or is this a leak under our home? Any way to test water to see if it is from the city water? New homeowner and not sure what to do next.