I live in a vintage Chicago 6-flat built in 1901 which was rehabbed in 1996. The main water heater to the 6 units was replaced at that time (now 11yrs) and has been working well. A plumber came by recently and noted our water heater was set at 140 degrees, 20 degrees higher than recommended 120 degree temperature. The 2 units on the 3rd floor (highest of
the buliding) have noted that the water temperature of the showers is uncomfortably lower since changing the water heater to 120 degrees. I have questions abouting water heating:

1) Does it make a difference how far you are from the water heater regarding temperature? Our vintage building is poorly insulated even with the rehab. If the water heater
starts at 120 degrees and people take showers at the same time - how long can we expect hot water traveling
through 3 stories and 6 units from at 40 gallon unit?

2) My dishwasher booklet does not indicate whether it has a booster with it that makes dishwashing safe < or equal to 140 degrees. Any way to find out?