Performed a heating pm on an oil boiler. Brushed and vacuumed. Replaced the oil filter, nozzle and strainer. Started and checked the safeties. Performed a combustion test. 9.2% o2, 23 ppm, 84.6% efficient System is operating properly. There is a slow drip on the bottom of a solder joint when the system cools off. Recommend replacing the fitting and the circulator gaskets on all 4 pumps.