Radiator Valve Leaks

Problem: Radiator valve leaks around stem, dripping onto floor.

Background: If you have an old- style radiator that has a valve which is leaking, take care of the problem as soon as possible. The leak can damage the floor, and even the ceiling below the radiator. Often valves leak around the stem because the packing inside the packing nut is worn or insufficient, or because the packing nut itself is loose. First try tightening the packing nut. If the leak persists, you will probably have to repack the valve stem. Many older radiator valves were built so that the packing nut can be raised without lowering the pressure in the radiator. In a hot-water system, where the valve permits water or steam to escape after the valve is closed and the packing nut is loosened, the level of water must be lowered below the height of the valve by opening the system’s drain cock. With a steam system, first reduce the pressure by allowing the boiler to cool.

What to do: Two forms of packing material can be used to repack the valve stem: different size washers or packing cord. If you use washers, loosen the screw holding the valve handle, remove the handle and withdraw the packing nut from the stem. Take out the old packing and slip the new packing washers over the stem. (Use the right number and size of washers to fill the packing space in the nut.) If using cord, wrap enough around the valve stem to fill the packing space in the nut. The nut should be tight enough to keep water and steam from escaping, but not so tight that it keeps excessive friction on the stem when the valve is turned.

Special advice: With a steam-heating system, let the fire go out, or at least have a low head of steam, before starting to work on the valves. After the system is cool enough to work on, close the valve tightly and unscrew the packing nut at the base of the stem. Pack the space between the inside of the nut and stem with metallic packing compound, using a small screw driver. It may be easier to pack the nut if it is removed from the stem. To do this, remove the handle and lift the nut from the stem. After the nut has been repacked, screw it down tightly and refill the system, following the instructions in the owner’s manual.

Helpful hint: If you are unsure about proper procedures with an older heating system, call a heating equipment specialist. Don’t tamper unnecessarily with controls or mechanisms and have a qualified technician perform major repairs, replacements, and seasonal maintenance.