does it automatically fill up the tank of the water Heater?

Open the hot then the cold faucets & shower to blow out all the air from the system. Getting a jolt of air and a blast of water isn't fun either.

Just do what you do at a house.

I personally have always opened the relief valve just to make sure all the air is out. Probably not necessary though.

WyoTraveler wrote:
First time filling? Open a hot water fauset and allow the water to run to bleed any air that may be in the tank.

Yes (if not bypassed) and then what he said....

It won't automatically fill. You must make sure that your water heater bypass (if you have one) is set to the normal position. Then you should open a hot water faucet and wait for water to run in a steady stream from that faucet. To be absolutely sure that your heater is full, lift the pressure relief valve located at the top of the heater to make sure some water sprays out. You should periodically check this relief valve anyway so this will accomplish that as well as ensuring that the tank is full. After all this you can safely turn on your water heater.

First time filling? Open a hot water fauset and allow the water to run to bleed any air that may be in the tank.