Water heater spraying water out the top?

[Eleighwil]

Hi, we are trying to install a gas water heater and everything is going wrong. Yesterday we hooked up the water lines and today we realized that we needed to add in an expansion tank. The water in valve was shut off, but when we disconnected the line from the heater, pressurized water started spraying everywhere out the top. What on earth happened?

 

[sarg]

I'm guessing what happened was the reason you require the expansion tank ......... water heaters create system pressure.

 

[Twowaxhack]

Hi, we are trying to install a gas water heater and everything is going wrong. Yesterday we hooked up the water lines and today we realized that we needed to add in an expansion tank. The water in valve was shut off, but when we disconnected the line from the heater, pressurized water started spraying everywhere out the top. What on earth happened?

You didn’t open a faucet to relieve the pressure. Just closing the valve doesn’t relieve the pressure