hot water heater relief valve

coz

I understand what the valve is for and how to replace it but what is the root problem? What causes the pressure or temp to be too high?

oh'mike

Some times they just go bad---but usually it is one of these:

Heater is full of lime--covering and insulating the temperature control rod on the back side of the gas valve.

To much water pressure---no expansion tank in system---

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joecaption

Also failed thermostat causing an over heated condition can do it.
The water out of the taps should be 120 deg. any higher and there's a danger of burns. A simple check with a thermometer will tell you.

Hardway

how old is this water heater.