Replacing A Radiator Valve

by Josh on September 27, 2006 · 31 comments

in Uncategorized

There isn’t much that can go wrong with a hot water radiant heating system. It is basically a second plumbing network that just circulates water between the boiler where water is heated, and radiators that release that heat into the rooms. When trouble occurs, one common problem is failure of a radiator valve. Fortunately this problem is easily corrected.

The valve for the radiator in my office has been leaking slightly since we bought the house, allowing water to seep out around the stem leaving ugly rust and scale running where water trickles down the supply pipes. There’s no telling when this tiny leak could suddenly worsen and make a real mess, so I want to deal with it right away. Replacing a radiator valve is a simple plumbing job that took me less than half an hour with the system already drained.

Please note: I am not a plumber and I do not know all the proper terminology for the parts and process described below. These steps worked for me, but follow these instructions at your own risk.

Tools for the Job:

  • Two pipe wrenches
  • Spud wrench
  • Heat gun to loosen paint and expand plumbing joints
  • Teflon tape
  • Plumber’s teflon putty, aka “pipe dope”
  • Coarse steel wool and small metal brush to clean old pipe threads
  • Utility knife to score paint covering plumbing joints
  • New radiator valve (duh)
  • Safety gear: glasses, gloves, respirator if you suspect lead paint

Here’s the broken valve disconnected from the radiator. Note the rust and water scale on the valve and supply pipe. When disconnecting this union joint, remember that the nut is removed toward the radiator, not toward the valve (I’ve made that mistake before). Removal also goes more smoothly if you use the heat gun to expand the outside member of the joint to be unscrewed and then use the utility knife to score any paint that was lapped over the joint.

Old valve disconnected

Next remove the old valve from the supply pipe and insert the spud wrench. Whenever possible, use two pipe wrenches when unscrewing a fitting. Here I used one wrench on the valve to remove it, while I used a second wrench to hold the supply pipe stable. This lessens the chance the pipe will be bent or sheared when the valve is removed. The fitting that connects the valve body to the radiator is called a spud. It is removed using a spud wrench, which looks like a prop for some alien technology from a sci-fi “B” movie. The grooves down the sides of the spud wrench grip a pair of nubs on the interior of the spud when the wrench is inserted.

Spud wrench

Use one of your pipe wrenches with the spud wrench to remove the spud. Be sure to use the heat gun to warm up the radiator so the spud will come out more easily. Even after doing this, removing the spud still took enough torque to radially deform my spud wrench a bit. (Lousy alien technology…)

Removing the spud

With the old valve completely removed, now is the time to clean up any corrosion or paint around the joint and threads. Use a wire brush, steel wool and the utility knife to clean things up a bit. Take care to protect yourself and anyone else in the house from paint chips that may contain lead. Minimize dust spraying the surface with water during any fricton-based paint removal, and vacuum up paint chips and dust with a HEPA-filtered vacuum right away. Disconnect the new spud and nut from the new valve and wrap the spud threads with teflon plumber’s tape. Put a little pipe dope on top of the tape and install the new spud and nut using the spud wrench and pipe wrench. Make sure the nut is on the spud the right way before installing the spud.

New spud installed

Tape and dope the supply pipe threads and then install the new valve body following the two-wrench method used to remove the old valve. Tape and dope the threads of the union fitting between the valve and the spud and then tighten down the union nut. Wipe off any excess pipe dope and celebrate your accomplishment by reinacting your favorite sci-fi movie scene using the spud wrench as your prop: “Khaaaaaaaaan!”

New valve installed

The true test of any plumbing repair is whether it holds water. I’ll have to defer that step just a bit until I have a solution for the radiator I removed from the upstairs bedroom. I may not be completely ready for heating season, but at least I’m making progress.

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