Originally Posted by Great Horned Owl
Opening a hot water faucet will work just as well as opening the pressure relief valve.
Not necessarily. When I had my valves wrong on the first trip of the season- I would get cold out of my hot taps AND my HW tank didn't fill. I had to switch the valve and then I heard the HW tank filling via the pressure relief valve (at that point- you're probably right and the hot water tap would have been sufficient).
I only say it because I had a false sense of security because water was coming out of the taps. I thought my HW tank was full and was fixing to turn on the HW heating element. It wasn't until I checked the pressure relief valve did I call myself a dummy (and lucky had a mobile RV tech there for other issues that I got saved from burning it up).