Check your expansion tank, as stated above, if the expansion tank becomes full of water, there is no place for the heated water to go when expanded, and it will open the pressure relief valve. One other item, if you have hard water, the mineral deposits will eventually stop the pressure relief valve from properly closing, resulting in a slow continuous drip.
Hope this helps, and let us know what you find.
__________________
Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
|