I turned off my gas boiler for the summer. Turned the temperature up on the gas water heater. Have done this previously but this year my tenants (2 family house) is saying that her water is only warm. How can I tell if my water heater is working properly. It's about 6 yrs. Old. Thank youJeanette NYC

And this is an electrical question, how?

The easiest way would be to take a temperature reading on the hot water. Take a cup of hot water and put a thermometer into it.

I'm going to have this question moved into the Plumbing section so you can get some more appropriates suggestions.