How do I fix this problem? Tank is continually filling with water, therefore comes straight out of the overflow pipe - so we get cold water
If duo is turned off, water heats fine and we get hot water. Is this a valve issue?
Water Heaters - Water
Answers & Comments
Most certainly is
if the overflow is connected to a valve externally where there is a small lever that you can over ride the valve and let air/ water out replace that
they are non repairable as they are a safety valve and preset and will be in the vicinity or $90.00 aud to replace
if it is different call a plumber
you stated that the water comes out of the overflow pipe
here are some observation points
electric hot water systems rot the copper tank around the element area from electrolysis over time so leaks will be around the bottom of the tank
ceramic lined tanks will rust through where the ceramic liming has been damaged --unit dropped during transport
gas heated systems seldom suffer tank problems as they are mostly copper tanks
so from your statement it is leaking from the overflow pipe and that means the tank is secure
if it wasn't then you would be getting on the floor with no apparent leaks
next point a new system will cost over $500.00 AUD ( anything less than 350 liters is a power waste because you can get at least 4 showers , washing up and to washing machines before the element switches on)) plus the fact that now you are required to fit a temperature control valve so that the out let temp cannot exceed 75 degrees C ( it is supposed to be for baths, showers and hand basins but lazy plumbers fit it at the hot water system so everything is controlled to a maximum 75 C --one advantage is that you can turn the thermostat down to 75 C and the power bill gets cheaper
any way I digress --water from an over flow pipe is a valve and I suggest that you get a second opinion or a second plumber