Maybe, just maybe replace the P & T valve that is leaking? You'll probably want to add an expansion tank while you're at it since there is a PRV in the system. The valve costs about $10 at a hardware store.
If you don't understand what a P & T valve is and/or can't make a sweat joint then just call a plumber. Either way, your problem will be solved (and Jimbo and Grumpy will be happy if you call the plumber).