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What To Do When One Hot Water Radiator Doesn’t Get Hot

Confused because one radiator doesn’t get hot?

Does one hot water radiator refuse to heat up, even when the rest of the system seems to be working fine?

Chances are, there’s air trapped in the radiator, preventing the hot water from filling it properly.

This is a problem you can generally solve yourself by bleeding the air out of the radiator.

It doesn’t take long and can make a big difference.

Here’s what you need to do.

  1. Get your  radiator key
    • If you don’t have a key for your radiator, you may be able to find one at a local hardware store.
    • Some bleed valves even fit a plain screwdriver, so try this out before you buy. (The bleed valve is typically located just an inch or two from the top of the radiator.)
  2. Place a pan under the radiator, and a rag over the key, to catch any water that drips out
  3. Turn the key about a quarter turn to the left. You should feel air seep out. When water starts dripping out, turn the key back to its starting point.

Now that you have bled your radiator , it should fill with hot water properly again, and get warm when your heat is on.

It’s a good idea to bleed all of your radiators at the beginning of fall, so that you’re not in for a nasty surprise when you need to put your heating on.

If you release a lot of air from the system, you may have to add water back to the boiler to increase pressure.

If the radiator still does not get hot, there may be an issue with the pipes leading to the unit.


A few minutes spent bleeding each radiator can ensure that your radiators heat up and your home is warm when the weather turns cold.

If you need any help or advice on bleeding your radiators or when it comes to any aspect of your heating system, Contact Us at (651) 294-7798.

We cover Blaine, Bloomington, Brooklyn Park, Eagan, Edina, Hastings, Maplewood, Minneapolis, Minnetonka, Roseville, North Saint Paul, Saint Paul, Saint Paul Park, South Saint Paul, Stillwater, West Lakeland, West Saint Paul, White Bear Lake, Woodbury, and many more locations.

Can’t find your town listed? Contact us at (651) 294-7798 to tell us where you live, so we can help you.

Schedule a HVAC repair anywhere in the Minneapolis or St. Paul area today by calling (651) 294-7798 or by requesting an estimate online.


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1220 Cope Avenue East, Maplewood, MN 55109