Water – Why is water running into the water heater when cold water inlet is turned off


I'm installing a new water heater. The cold water inlet is turned off and no water is running in the house.

After attaching the hot water outlet to the water heater I can hear water flowing/dribbling into the water heater.

Does this mean I have a bad valve that is allowing cold water to back-flow to my water heater? I can't hear water flowing at any of my sinks, tubs, etc.
How could I find the bad valve.

Additional information: This has been running for over an hour and even with water heater off a small stream of cold water runs from all my faucets when I turn on the hot water side of the faucet.

Best Answer

This is because after turning off your water you still have water in the pipes. The water heater in most houses is at one of the lowest points in the house. Meaning that even after turning off water at tap and even after leaving a faucet open, whatever is lowest will still get what water is left in the lines.

It is funny because my new helpers go through this exact experience when prepping for plumbing work. And they are each surprised about the amount of water that is still left in the pipes (and more surprised that they have to clean it up).

What you are experiencing is normal and if the water heater is the lowest (gravity) or one of the lowest spots in your water line it is perfectly normal to hear water flow after it is turned off and then dribble for a while - takes 5-10 mins for gravity to works its way out sometimes.