Performed preventative maintenance for a peerless boiler system model #DE-06-SV-WPC, serial #5012116-200412. Powered the system down and removed the access panel. Removed and cleaned each burner and cleaned out the burner box. The water pressure is at 15 psi and the limit is set for 170°F. The leak is actually coming from the relief valve. It seems that the relief valve has opened at some point and has had a very small drip since then. The expansion tank is in good condition. I powered the system up and called for heat at each zone. I observed the system starting normally and took a combustion analysis test and received the following readings, o2 is at 11% and the co levels are at 19ppm. The system is operating properly at this time. Recommend replacing the pressure relief valve on the system to stop the dripping.