I was called to a home to perform a preventive maintenance check on a natural gas, hot water, Viessmann boiler, and indirect water heater. The boiler was producing a loud banging noise, and the water heater was not producing hot water. I inspected the boiler and found that the burner was not igniting, which was causing the loud banging noise. I replaced the burner and the boiler started working properly. I also inspected the water heater and found that the heating element was not working properly, which was causing the water heater to not produce hot water. I replaced the heating element and the water heater started working properly.