I am a painting and carpentry contractor and have done other handyman jobs for years but have a problem. In a house we bought to rent out I hired a contractor to do the renovations and paid little attention as it went along (MISTAKE). There was a leak in the supply line, he brought in a plumber and said it was taken care of.

The contractor installed a hot water heater.

Once the job was done there were several problems one of which was related to the water heater ( no unions installed, TPR valve not directed to the floor, no overflow pan, etc).

While I was correcting these problems I noted that with the water on at the meter and off at the cold water inlet to the water heater there was a small flow of water into the heater (can hear it dribbling in), when I disconnected the union at the hot water outlet there was a steady small flow of water and the flow that could be heard from the water heater stopped. If the hot water outlet pipe is obstructed there is a build up of pressure in the pipe so it does not appear to be simple drainage from the other pipes. Flow from the cold water inlet side is normal not just a dribble.

The house is approx. 50 years old, is one level and the water heater plumbing is the highest point in the system and the new plumbing all seems to be connected in the correct order -- no cross connection of hot to cold.

Looking under the house the leak corrected by the plumber originated in a 3/4" galvanized pipe which was 1-2" below ground and was corrected by using a twist on plastic pipe repair unit and does not appear to be leaking -- this pipe continues on to supply a toilet. 2-3" below the repaired pipe there is a 1/2" copper pipe which was tapped into to supply the water to the rest of the house (using 1/2" CPVC which approx. 10- 12 feet further down the line is then converted to 3/4" pipe and enters the wall to supply the water heater (within this same wall is the plumbing for the kitchen sink and a bathroom lavatory.

To further complicate matters when the tank is full and air pockets purged from the water lines and no visible leaks in any of the plumbing there is an intermittant flow of water at the meter which amounts to approx. 0.4 gallons over approx. 20 minutes.

My first question is what might be the cause of the back flow into the hot water outlet line.

The next question I don't want to ask -- the leak.

Thanks for your help,

Bill