"Mark M." wrote in message
...
Yes. Turning off the main water valve could cause the water heater's
relief valve to open. Here's why: water expands when heated. The extra
volume has to have somewhere to go. With your main valve open, this extra
volume goes back into the water main feeding your house. With the valve
closed, this extra volume has nowhere to go but out the pressure relief
valve on your water heater.

Yes, that was the source of the water.