For this job I performed a complimentary plumbing inspection. Customer was having an issue with one of their tandem water heater set up. Stating water would get lukewarm towards end of shower. While performing the inspection on the unit I noticed that the gas control valve was in the pilot position. I turned the knob to on, the unit fired up immediately. Tested the units to ensure proper functioning. Made recommendation to customer, really need to consider getting new units, both units are 19 years old.