From time to time my Overflow Pipe runs with a vast amount of boiling water until no hot water is left in my geyser. I will then climb into my roof switch the cold water tap feeding the geyser on and off (while leaving my hot water tap on for the bath)-to try and shock the pressure valve (in case there is dirt or something in it), and adjust the thermostat, whereby the problem seems to rectify itself. Could this be a thermostat problem whereby the temperature is not being controlled sufficiently, or could it perhaps be a faulty pressure valve?

Hi Vaughnrb


Could be a faulty pressure relief valve...

Could be a faulty thermostat...

Could be a faulty expansion tank, if present, too.

You could try taking pressure readings at your water heater using a hose-bib pressure gauge... see what happens to pressure during the heat cycle. That should tell you more on this.

Taking the temperature using a thermometer after the heat cycle and adjusting the thermostat may also help.

The most quick fix in most cases would be to replace the temperature and pressure relief valve. However, if you have an expansion tank, I would take this out while changing the relief valve and check to see if the diaphragm has burst (or the tank is filled with water).

If you have an older style expansion tank it could just need to be drained to resolve your issue!

No matter what, you need to change out the temp. and pressure relief valve as this will not reset properly once disturbed.

Hope that helped!

Mark

If your T&P valve is discharging boiling water then it's doing the job it was designed to do. And that is to protect your system.
I opt for Marks second choice which would be a fault thermostat. Have it checked out. Good luck, Tom