Hot Water Boiler. DHW water heater tank. Perform a tune-up and cleaning to help ensure reliable and safe operation. Inspect for cracks & deterioration of Heat Exchanger. Check and clean Burners, brush and vacuumed-ok Check and clean flame sensor and ignition Assembly-ok Check Safety Controls-ok Check electrical wiring and components-ok Check water feeder-ok Check back flow prevent-ok Check expansion tank-ok Check relive valve-ok Check Gas valve & Gas Line-ok Check Combustion Air, Flue pipe-ok Check Temperatures & Water pressure settings; Performance-ok Check and run Thermostats-okay Check circulation pumps-ok Perform inspection on a DHW tank. Check for water leak, no leakage at this moment. Check water valves-oKay Check ST-12 exp-N/A Check control gas valve-okay Check gas line- no leaks at this time Check Draft and combustion-okay Run and monitored for good operation-ok Run system, check hydro, all of them getting hot, left system operating well at this moment.. Perform maintenance