I woke up today to a full drip pan under the gas water heater and my utility room slowly flooding with water. Of course the drip pan was never connected to a drain and overflowing. 

After shutting off the water to the water heater the flooding stopped completely. I did some investigation and noticed **whenever I manually open the top mounted pressure valve I can tell that some water is discharged through the connected pipe, but I can also hear an amount of water flowing down somewhere inside the water heater**. I cannot see any water or wetness when looking closely at the valve connection at the top. I am not sure where the water could be leaking inside the unit. 

Could it help to replace the pressure valve? Is it likely there is a hole in the tank somewhere, but if so why doesn't it leak all the time but only when I open the pressure valve?

I am planning to buy a pressure meter today and check the house water pressure as well as test the pressure on the heater when I reopen the water supply. Will update later with readings.

[![enter image description here][1]][1]
[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/c1zM7.jpg
  [2]: https://i.sstatic.net/czccO.jpg