We have a two year old, 100 gallon, 199,900 BTU natural gas, American Standard water heater supplying hot water to a 7 unit apartment building. Installed with the water heater is a recirculating pump. Each unit has one bathroom/tub/shower. Recently, the hot water supply has been intermittent. I completely drained the water heater, vacuumed out the sediment, then refilled. I set the thermostat to 120. People were still complaining that the water wasn't hot enough. So I raised the temp to 130. Less complaints now but there are times (one person says they have good hot water in the morning, but none in the evening) when people say they run out of hot water. I called the water heater company for some tips and was told that if some of the units have a single handled faucet in their sinks, the hot and cold water might be mixing together causing the problem. I know that several of the units do have these single handled faucets and I should have taken detailed notes when I talked to the tech as he explained how to troubleshoot this particular problem. So what is the step by step procedure to pinpoint this type of problem?
Thanks for your reply.