Gas Water Heater Condensation
I have an 8 year old gas hot water heater with a power vent and a condensate drain portal at the base of the vent pipe. The unit has worked fine with no condensate for all 8 years. We took a week's vacation. Before we left, I turned off the water pressure to the house. I always do this, as a precaution in case a toilet supply line, dishwasher or washer hose were to burst while gone. No water was consumed while we were gone.
I turned the house water back on when we returned. All seemed fine with everything. The day after we got back, I noticed that the condensate drain line creates and drains a large amount of water whenever the hot water heater fires. It drains condensate continually until the heater stops firing. It drains as much as a gallon in about 20 minutes.
The water heater seems to function normally in all other respects.
What is causing all the condensation? I need to run it to a floor drain with a length of tubing. I never had any condensation before.