Rheem power vent 21vp40e-1a
I have a rheem power vent 21vp40e-1a my problem is a decline in the amount of hot water I get out of it. Once it begins to heat, the burner will light run for a few seconds and then shut off this will continue for a long time, then eventually it will stop. The amount time that the burner lights varies but it's usually less than a minute. I've checked for obstructions of the pvc vent, and I've bypassed the vacuum switch by jumping the wires, and the problem continues anyone have any more advice on this or dealt with the same issue?