Replacing a house radiator is a fairly straightforward project that even a first time DIYer can handle. The process consists of three parts: draining the old radiator, removing the old radiator, then installing the new one. The main thing to be aware of when replacing a house radiator is to ensure that you have the heater off and the water supply valves shut off when removing the old radiator. Otherwise, you could wind up in a room full of water.
Turn off the boiler at the switch on the unit or at the main circuit switch.
Place a dropcloth or plastic sheet on the ground underneath the radiator you are replacing.
Close the valves at either end of the radiator by turning them clockwise. In most installations, the inlet side will have some kind of thermostat control that you can turn by hand. The other side will have to be closed with a wrench.
Open the radiator bleed screw, located at the top of the radiator, with a radiator bleed wrench. This will release the pressure in the radiator.
Place a bowl or container under the drain valve. This will be attached to either the inlet or outlet valve to the side of the radiator. You can identify the drain valve because it will be positioned horizontally, while the inlet and outlet valves are vertically mounted. Open the drain valve. Allow the water to drain into the bowl. Close the drain valve as needed to empty the bowl.
Unscrew the two union joint couplings at either end of the radiator. These are attached to the inlet and outlet valves. Use a pair of pliers to hold the valve steady and another to open the coupling. This will help prevent damage to the pipes.
Loosen any brackets holding the radiator to the wall. Lift the radiator up and out of the way.
Insert the new radiator into any wall brackets, if present.
Wrap the inlet and outlet on the radiator with plumber's tape.
Screw the union couplings onto the inlet and outlets on the radiator. Tighten with the wrench.
Open up the valves at either end of the radiator.
Turn the heating system back on.
Bleed your heating system after replacing a radiator to ensure that water is being distributed evenly throughout the system.