On hot water demand burner ignites but will not stay lit.If at the same time you
Open the pressure relief valve the burner will stay lit a bit more.Please help.





Thanks, Kevin

Water heaters have a pressure switch that is sensing the water pressure in the outgoing hot water pipe.
If the hot water taps are all closed, that pressure is high.
As soon as you open a tap, the sensor sees that there is a water demand and activates the heater system (it ignites the burner).
However in this case the demand seems to be so much reduced that the pressure in the outgoing hot water pipe gets the chance to raise itself to a level that forces the burner to cut-off again. (That is a safety measure to prevent overheating of the system).

Somewhere in the outgoing water pipe there must be a restriction.
Perhaps :
-A valve partly closed?
-The hot water tap not fully open?
-Is there an outgoing water pipe valve near the heater that is partly closed?
-Do you note a clearly reduced water flow from the hot water tap?

Please let me know, so that I can advice you further!
;)