water leaking from tube

[sartis]

Hello, I have a clear tube that is coming off the cold side of my hot water heater, see attached photo. It runs down to the drain on the floor, it is always leaking a little water.....Can anyone help me understand what it is and if I can stop the flow of water.

Thanks in Advance.

Steve

 

[dino]

Temperature and pressure relief valve! Install a thermal expansion valve or a potable expansion tank on cold supply. Could also be to much pressure, check prv