Water Heaters - Running water in my heater

I have a new home and over the past two days I have discovered a running water sound in my bathroom wall. I thought it was in the toliet but have realized that it is coming from the hot water heater. There is constant movement of water in the hot water line. It started faint then has gotten a lot stronger. As of tonight, I have called the installer to call me in the morning but I also cut the water intake on the cold line and shut off the power to the unit. There are no wet spots on the wall or floor.
Any ideas to what might be the problem?
Please help.

It sounds like a leak in a line. Only other thing I have seen is if the temp/pressure relief valve is piped away from the WH, if it releases, you would hear (but not see) water running. You did the right thing by making the call. good luck.