Steam boilers transfer heat through radiators placed in each room, unlike forced air central heat, which involves warming and circulating air through vents throughout your home. The boiler heats water until steam rises through the system, warming the air. As the steam cools and returns to water, the pitch of the piping system carries the water back to the boiler, which reheats it to steam and the process continues. After decades of use, cast iron steam radiators can corrode and block up, causing noise, poor heating or no heating at all. With only a few tools, you can replace a central heating radiator.
Turn the boiler thermostat down all the way and turn off the electricity if applicable. Not all steam boilers operate on line voltage.
Allow at least an hour to let a warm or hot boiler to cool down before beginning your repair.
Locate and turn clockwise a knob similar to a garden spigot on one end of the radiator, down low by the floor. Check the opposite end of the radiator. If another pipe is leading out, you have a two-pipe steam system, which adds a small amount of additional work.
If the radiator has a drain valve underneath, open the valve and drain as much water out as possible. Note that many old radiators are rusted and plugged up and unable to drain themselves through conventional methods. Have towels handy.
Find the couplings at either end of the radiator that connect it to the supply valves. Use your pipe wrenches to loosen them. One-pipe systems will have one valve and coupling at one end of the radiator.
Remove the old radiator.
Set the new radiator in place and line up the piping system.
Apply two turns of plumber's tape to the radiator's threads, then tighten the coupling in place using your wrenches. Open both valves.
Turn the your boiler on and check for leaks, tightening as needed. Make sure the entire surface of the radiator gets warm.