How to Turn On a Radiator and Heat Up a Room in 8 Steps

Before turning on a radiator, ensure your heating system is off. You’ll turn your water-circulating or steam heat system on and off throughout this guide, so follow the steps carefully. When turning the system off, wait for the radiator to cool down completely before proceeding with the next step to avoid injury.

To turn on a radiator, start by rotating the control valve near the bottom of the radiator where the hot water pipes connect to it; you may also find a temperature dial (if it’s a thermostatic valve). Turn the control valve counterclockwise to open it, and make sure it’s open all of the way so the radiator can reach its maximum temperature.

Turn your heating system back on and determine if there is heat coming from the radiator. If the radiator is still cold after the system is up and running, proceed to the next step.

If a radiator is still not working after turning on the control valve, it may need bleeding. Bleeding a radiator means letting out any trapped air or clogged water. Find the radiator's bleed valve with your heating system turned back off and completely cooled down. This valve is usually at the top of the radiator on either the left or the right side.

You will use a radiator key, sometimes called a bleed key, to turn the bleed valve. If you don’t have a radiator key, you can pick one up at a local hardware store or online. Sometimes, needle-nose pliers can turn the valve, or a flathead screwdriver might fit into a slot at the top of the valve.

Before turning the valve, hold a towel, small bucket, or cup beneath the valve to catch any drops of water. Using your radiator key (or pliers or screwdriver), slowly turn the valve counterclockwise about half a turn.

As you open the valve, you’ll hear a hissing noise as air escapes from the radiator and water fills the space within the system. Once the hissing stops and a steady stream of water starts coming out of the valve, it’s time to close it in the next step.

Again, using your radiator key (or pliers or screwdriver), turn the bleed valve in the opposite direction (clockwise) to close it. Go slowly and be careful not to break the valve. You do not need to force the valve closed—stop turning once you feel a bit of resistance. Use your towel to wipe away any remaining water on the radiator.

Take the time to bleed the rest of the radiators within your system to ensure they aren’t causing any more common home radiator issues. Experts recommend bleeding all of your radiators twice a year to ensure they produce plenty of heat and to reduce the pressure in the heating system.

After bleeding all of the radiators, turn your heating system back on. Check your boiler pressure gauge—it should be between 1 and 2 bars. If the particular radiator you want to turn on is still not producing heat, turn your system back off and move on to the next step.

About halfway down the side of a steam radiator, there will be a metal air vent. This vent is usually cone-shaped and has a small hole at the top. If the vent is clogged, the radiator won’t get hot. Use a small wire or sewing needle to puncture the hole at the top of the air vent. Also, ensure the vent is positioned vertically with the tip of the cone facing up.

With the air vent cleared and re-positioned, turn your heating system back on and determine if the radiator is heating up. If clearing the air vent did not fix the issue, you may have a larger issue that requires the assistance of an HVAC professional.

If your radiator is still not heating up after trying all the methods in this guide, it’s time to call in the professionals. An HVAC contractor will inspect your steam heating system as a whole and can take apart the radiator to find any internal issues.

In a worst-case scenario, you may need to replace the entire system. Steam radiators can last decades, but there will come a time when you’ll need to swap out the system for a new one.