How to Fix an Old Steam Radiator Leaking from the Valve

My house is pretty old, and it uses steam radiators and a gas boiler for heat. This is effective enough, but there are a few problems. Some of the radiators and pipes are noisy (read my thoughts on silencing those old radiators here). They also tend to break down and start leaking.

The first year I lived in the house, I had a few radiators with tiny leaks around the stem of the intake valve. That wasn't a big deal, and I simply re-packed the the valve stem with some graphite packing. This worked for some of the radiators, but recently I had what you might call a catastrophic failure in one of the valves.

Steam was hissing out, and a slow drip turned into a steady leak that covered my kitchen floor with water. Eugh. Time for more drastic measures.

Changing the Valve on a Steam Radiator

The solution here isn't all that expensive - change the entire valve. The problem is that repacking the stem is somewhat temporary, as it isn't as good a seal as the original gasket inside the valve. Depending on the size of your pipe (mine was 1"), the new valve should only cost you about $15 to $20.

First, disconnect the valve from the radiator. There's a large nut that screws from the radiator (or, technically, from the union joint inserted into the radiator) onto the valve. Loosen this nut and move the radiator out of the way. If you're confused about which way to turn the nut, turn it counter-clockwise from the perspective of looking into the valve from the radiator.

Now, you need to remove the old valve. This is hard part. If it's like mine, it's pretty well tightened and sealed up. I tried a lot of things when I did this the first time, and only one thing worked: a cheater bar. I attached a long pipe (mine happened to be about 4 feet) to the end of my pipe wrench and that gave me enough leverage to loosen the connection.

To remove the valve, first tighten a pipe wrench around the pipe underneath the valve. This will help stabilize the pipe so you don't twist it while you're loosening the valve. Then, tighten a second pipe around the valve itself. If you can't break the connection and unscrew the valve, attach a cheater bar like I did... it will eventually give.

With the old valve removed, you're ready to screw on a new one. Apply some pipe dope (or teflon tape, if you prefer) to the threads of the pipe. Carefully hand-tighten the valve and be sure that you get it on straight and threaded properly. You don't want to over-tighten this, because you need the valve to point in a specific direction... where your radiator is going to be. Hand tighten the valve until it's in the proper position and then take an educated guess - if you can get another full rotation, go for it. If not, leave it alone.

Finally, apply some pipe dope (or teflon tape) to the threads on the valve. Position the radiator next to the valve, and slowly hand-tighten this connection. Again, be sure to seat the threads properly... if they aren't, you'll have leaking. This time, I typically hand tighten it as much as I can and then give it a little extra torque with the pipe wrench.

Note: If it looks like you have a nut on both the radiator and the valve, that means your valve came with an extra union joint. Unscrew that from the new valve, and you should be left with a set of male threads that will connect to the union already on the radiator. Trust me, it's more trouble than it's worth to try to remove the old union and use the new one... I tried.

And that's it! Go turn the thermostat back up and watch your new valve to make sure it doesn't leak. If you mis-threaded any of the connections, it's possible that a leak could develop, in which case you should just disconnect everything and connect it again more carefully.

By the way, you did make sure to turn off the boiler (or at least turn down the thermostat) before you started working on the radiator, right?