I was called to a home to perform a preventive maintenance check on a Viessmann natural gas boiler and indirect water heater. The boiler was over 10 years old and had not been serviced in several years. I inspected the unit and found that the burner was not firing, the gas pressure was low, and the water level in the indirect water heater was low. I replaced the burner and adjusted the gas pressure and water level and tested the unit to ensure it was working properly. I also provided the homeowner with a maintenance checklist to help them maintain the unit in the future.