The paper I read from Dr. Falkenheim at Virginia Tech says to keep your water heater at 140 degrees Farenheit. He also says to drain your water heater once a month. Yes, it's hot, but apparently that is the temp needed to keep the water heater from becoming a breeding ground. We set our water heater at that temp and have simply adjusted by adding more cold when needed. We also give our guests a heads up so they don't have a problem washing their hands.