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How To: Repair a Noisy Radiator

noisy radiator

While they certainly keep us warm in colder months of the year, radiators are not without their faults. In the winter they can be slightly annoying or downright infuriating! They whistle, they squeak, they clang, they bang. Luckily, it’s pretty easy to repair and you can silence noisy radiator without calling a professional.

If you are having trouble with your radiator at the start of the heating season it may simply need to be bled and you can find those instructions here.

First things first. Let’s make sure you have a steam radiator and not a hot water radiator. The easiest way to tell is to have a look at the number of pipes coming from the radiator.

One pipe coming from the radiator is always gonna be a steam system, while two pipes are a little trickier, as it can be either. Assuming you do have a steam radiator, you can move on with the steps included here.

What Causes a Knocking Radiator?

When you hear an obnoxious banging or knocking sound coming from your radiator, it usually is the result of water that has gotten trapped in the pipes. When steam begins flowing into your radiator, the air vent on the side of the radiator begins to hiss quietly. Once the radiator is filled with steam, the vent closes and the stem then releases the heat into the radiator, which then heats the room through radiation and convection. 

As the steam travels through the unit, it eventually cools down and turns into condensation. The condensation goes back through the unit and back into the boiler. Got it? Good!

If your radiator is tilted the wrong way, the water gets stuck inside the radiator. Then whenever steam rushes through the radiator, it pushes the water forward rapidly, causing it to slam into a valve or an elbow. This produces that loud knocking noise you know and hate.

How To Fix Knocking

To stop this knocking, you’re gonna have to shim up the bottom end of your radiator and make sure water is draining out. Here’s how:

  1. Make sure you turn the thermostat all the way down to prevent the boiler from turning on.
  2. There will be a large nut that connects the radiator to the steam pipe: loosen this, and be careful to not get burned by any hot water.
  3. Raise the bottom end of the radiator and slide a couple of wood blocks underneath. 
  4. Lay a level over the top of your radiator just to ensure it’s angled slightly back towards the boiler.
  5. Tighten the nut back onto the steam pipe.
  6. Turn the thermostat on and check for leaks.

​If you’re still experiencing the knocking noises after following the steps above, it could also be caused by water trapped in a sag (sagging pipe). This is also an easy fix. Just check all your horizontal steam pipes and, if need be, raise them, making sure they are in a straight and level position.

How to Fix Squeaking and Whistling

If your radiator is squeaking and/or whistling, this is more than likely an air vent issue. The air vent is attached to a pipe at the bottom of the radiator. Replacement air vents are less than $30 on Amazon or your local plumbing supply.

It will also be a good idea to grab some PTFE tape (Teflon tape) and graphite packing. Once you have grabbed your supplies, you’re ready to work!

  1. Just as before, shut the thermostat off.
  2. Hold the new air vent upside down and wrap the PTFE tape around the threaded stem (this should be facing upwards).
  3. Twist off the old air vent. It is recommended to cover it with an old thick cloth, turn counterclockwise, and be aware that if you apply too much pressure, the vent may snap off.
  4. With the old vent out, thread the new air vent into the radiator. Be careful not to cross the threads.
  5. Tighten the vent until it is vertical, being careful not to crack the vent.
  6. Grab a screwdriver and unscrew the handle from atop the radiator valve. 
  7. Then grab a wrench to loosen the nut that connects the valve stem to the valve.
  8. Wrap graphite packing around the threaded portion of the valve stem.
  9. Thread the packing nut back onto the valve and tighten it with the wrench.
  10. Screw the valve handle back onto the valve.
  11. Turn the thermostat on and check your work for leaks. 

​That’s it! Enjoy the sound of silence. Assuming you’ve done everything right, the new vent will allow trapped air to escape, which will reduce the chances of finding yourself with a noisy radiator.

If this didn’t solve your noisy radiator issues, then maybe it’s time to call around and get some quotes from a professional. If you feel uncomfortable doing any of these DIY fixes, there is no shame in calling in reinforcements in the form of a pro.

You can also go even further to really spruce up your radiator and give it a full restoration by following the steps in this post How to Paint an Old Radiator.

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