How to Repair a Leaking Radiator Intake Valve

A common problem among old, unmaintained radiators is a leaky intake valve. The point at which the steam enters the radiator may leak water and/or steam - creating noise, leaving a mess, and hurting the efficiency of your heating system.

Luckily, it's easy and cheap to fix. You'll need a couple basic tools, some cheap materials from your local hardware store, and not too much time.

How Does a Leaky Valve Impact Your Efficiency?

When you heat your house with a steam radiator system, you're trying to distribute the heat from your boiler's flame to the rest of your house. The flame converts water in the boiler to steam, and that steam is sent to the radiators to slowly radiate heat into the rooms.

For this system to work properly, the steam needs to stay inside the system. It will circulate throughout the radiator and condense into water once it loses enough heat. In a properly functioning system, the boiler will kick in every once in a while as the pressure drops - but not constantly.

A leak in the system - such as an unsealed intake valve - allows steam to escape. This requires the boiler to kick in more often to replace the lost steam. That means more burning - and more oil or gas used up. You're spending more on fuel, and getting less out of your heating system.

What Do I Need to Fix the Leaky Valve?

First, you'll need a few simple tools. A screw driver (may be a flathead or Phillips head, depending on your valve's handle) and a wrench (preferably an adjustable crescent wrench). You may also need needle nose pliers and a utility knife, depending on how old and worn out the current gasket is.

As for parts, you need one thing - graphite valve packing. It looks like a piece of black, rubbery string. Chain hardware stores (Home Depot, Lowes, etc) will probably stock it in small blister packs that cost $2-3. It's usually located in the plumbing section with other parts necessary to replace or repair valves. See the attached picture to get an idea of what you're looking for.

One pack of the graphite valve packing will probably be enough to fix three or four valves. You should have plenty left over for the next leak.

How Do I Repair the Leaky Valve?

To repair the valve, you're going to need to remove and replace the gasket inside the packing nut. This seals the valve's connection and prevents steam from leaking out.

First, close the intake valve on the radiator. As a precaution, you'll probably also want to turn the thermostat down so that the boiler doesn't kick in while you're working.

Find the screw that holds the handle onto the intake valve. Unscrew it and you should be able to remove the handle.

You should now be looking at a stem with a nut at the bottom. That nut - the packing nut - needs to come off. Use your crescent wrench to loosen the nut all the way and remove it from the stem.

Next, remove anything inside the packing nut. Ideally, there should be a rubber gasket that you can easily pop out with your screwdriver or with some needle nose pliers. If the gasket has started to deteriorate, you may need to scrape it out with a utility knife. If you're having trouble getting the gunky build-up out of the packing nut, you can probably find a replacement at Lowes or Home Depot - but with enough patience you should be able to clean it out.

Take the graphite valve packing out of the package and gently loop it around the stem three or four times. Make sure that the loops go around the stem clockwise - the same way that the packing nut is threaded.

To keep the packing in place, use your screwdriver or utility knife to press the beginning of the string into the stem. Also be careful not to pull it tight as you loop it around, or you'll break the string of graphite packing.

Finally, re-assemble the valve. Tighten the packing nut over the stem - it will compress the valve packing into a new gasket. Then re-attach the handle that you removed in the beginning.

Open the Valve and Fire It Up!

With a new gasket in place, your valve shouldn't be leaking anymore steam. Open the valve up, turn the thermostat back on, and watch the steam roll in.

Enjoy the heat - and the fact that your system will be a bit more efficient!