I have 2 pressure gauges on the system. Never read over 15psi. I have an expansion tank in place. I tested the relief valve when i flushed the boiler. I do this every fall. PRV said it is rated for 30psi. It is leaking mainly during fire up to temp (assuming as pressure builds). Never over 15 psi according to the gauges. Sounds like an end of life PRV and just replace?