How to adjust radiators

Updated June 29, 2018

Balancing radiators in a heating system is necessary to maintain the same temperature in each area the radiator heats. Water entering a radiator travels through the grilles on one side and exits the other side of the radiator at 11 degrees Celsius ( 20 degrees Fahrenheit) cooler. Each radiator in the line will be this much cooler, resulting in colder rooms as the water travels to the end of the system. Three radiators result in a 15.5 degrees C (60 degrees F) temperature drop from the first to the last. Adjusting all radiators in the line of service will keep all rooms at a constant temperature.

Turn off the radiator heating system and wait for it to cool completely. Balancing radiators requires no heat to start the process. Locate the radiator closest to the heat pump or boiler.

Pull the black plastic cap off the lock shield valve on the side of the radiator closest to the heat pump or boiler. Pull the cap upward to remove it and set it aside.

Remove the cap off the control valve on the opposite side of the radiator in the same manner. Set the cap aside.

Open both the lock shield valve and the control valve fully by turning the adjustment bars. Use pliers to turn the bars fully counterclockwise to the open position on each. Remove caps off all radiators in the system and open the valves, using this method.

Clip one radiator thermometer on the pipe that connects the lock shield valve to the radiator. Clip one radiator thermometer on the pipe that connects the control valve to the radiator. Start this process with the radiator that is first in the heating process closest to the heat pump or burner.

Turn the heating system on. Close the lock shield valve with pliers by turning clockwise until it is almost entirely closed. Gradually open the lock shield by turning it counterclockwise as the heat increases. The temperature difference from the lock shield valve to the control valve must show an increase of 11 degrees Celsius (20 degrees Fahrenheit).

Remove the thermometers from the first radiator and continue this procedure for the next radiator in the line. Attach the thermometers to the radiator and open the lock shield valve slowly to achieve the same temperature on the first radiator at its lock shield valve. Adjust so there is an 11 degrees Celsius (20 degrees Fahrenheit) difference on this radiator also.

Adjust each radiator in the line in this same manner until all radiators balance. Replace the black plastic caps on each end of each radiator by pushing them straight down.


Balancing a radiator heat system will hold the adjustments in place until replacement of pipes or radiators. When installing replacements to the heat system, the system will need rebalancing.


Take care not to touch the radiators when making adjustments as they can cause burns. Only touch the pliers to the adjustment bars and the thermometers.

Things You'll Need

  • 2 radiator thermometers
  • Pliers
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About the Author

Mary Lougee has been writing for over 10 years. She holds a Bachelor's Degree with a major in Management and a double minor in accounting and computer science. She loves writing about careers for busy families as well as family oriented planning, meals and activities for all ages.