Things You'll Need
When you drain your hot water heating system to clean the supply tank or to perform other repairs or maintenance, you will need to add water back into the system. The process of adding water to a heating system involves keeping as little air as possible from entering and getting trapped in the system. You can add water to a heating system by making sure that you can open the valves on the radiators.
Open all of the shut-off valves to the radiators that are used with the heating system and make sure all of the air valves are closed. Turn the lever on the valve to the left to open the valve.
Close the air valves using a screwdriver or a pair of needle-nose pliers and turn the valve clockwise.
Open the water supply shut-off valve on the supply tank to allow water to enter the system.
Locate the radiator that is closest to the boiler for the heating system and open the air valve. Use a screwdriver or a pair of needle-nose pliers and turn the valve counterclockwise.
Wait until water begins to come out of the air valve and then turn it clockwise to close it.
Repeat steps 4 and 5 on the remaining radiators in the home until they are filled with water.
Use a cup to catch any water that comes out of the air valve.
If you leave the shut-off valve closed on any radiator, it will not get any water.