How do I tell if a pipe running through a cinder block wall is leaking?
Turn off all faucets, and devices in the home that might use water. This includes, but is not limited to ice makers, dishwashers, clothes washers,  faucets, running toilets, etc.

Use a little piece of tape, one of those "sign here" stickers, or something similar to mark the water meter reading (or if it's digital, just write down the reading).  Don't use any water for an hour or two, then go back and check the meter.  If it's changed, you either have a leak, or forgot to turn something off that used water.