In addition to the difficulty of removing the equipment, replacing a radiant heat system leaves a person with the question of what to do with all the those old radiators. Fortunately, radiators can sell for quite a lot of money, especially if they are cast iron. Removing them is mainly a task of draining water and disconnecting pipes, which can be done easily with items found around the house.
Close the manual valve on the side of the radiator by turning the cap clockwise. Close the lockshield valve on the other side of the radiator with a wrench by turning it clockwise.
Put down dust sheets to protect your carpet around the radiator. Place the plastic bowl beneath the drain off valve under the lockshield valve, if your radiator has a drain off.
Loosen one of the union nuts on the valve if you do not have a drain off valve. Fill the bowl with water and empty it as often as needed. Remove the bleed valve on the top right corner of your radiator with the radiator bleed key to replace the water in the radiator with air.
Clamp the valve with water pump pliers and loosen the union nuts with a wrench. Put a cap on the valve, if it is thermostatic, to prevent leakage. Wrap a plastic carrier bag around the valves to prevent dirt or dust from getting inside them.
Move the bowl under the actual radiator to catch any more water runoff. Remove the largest union nut by the lockshield valve. Lift the radiator up off of the brackets.
List your radiator on eBay, craigslist or another local auction site. Take it to a local junkyard to sell for scrap, if you prefer not to go to the trouble of selling it online.
It is absolutely vital to cap off the main valve. Major flooding has been known to occur from radiators.