How To Flush Boiler Systems

Most boilers will require that you flush them out every few months. This will help to remove rust and sledge. These materials can cause corrosion and eventually damage the entire unit if it is not removed. It will also cause it to run horrible and you could waste a ton of money in energy bills trying to keep it running. In some cases it is important to flush out new boiler systems that have just been installed.

What You Need

  • Hose pipe
  • Jubilee clip
  • Radiator key
  • Wooden rod
  • Stiff wire

What To Do

First you need to turn the power off to the unit. If it is a gas boiler you need to shut off the flow leading to the boiler. Find the expansion tank that is in the loft and turn it off. This is going to be the smaller tank. Block the water valve or turn it off. To keep water from entering the tank when you are flushing it out you must place wood across the tank.

Place a drain cock to a hose on the lowest part of the pipes with a jubilee clip. Run this hose outside. Make sure that it does not run over any sidewalks or roads where it can cause accidents. Open the drain valve using pliers.

Now open a bleed valve on each of the radiators to speed up the process. First open the highest level valve and work your way down to the lowest. Don’t open them too soon or you will push too much water out.

Look at the boiler to make sure that you have completely flushed it. There might be some air in the system that will keep some of the water from draining. If this happened than loose the ball cock in the header tank and allow in six inches of water.

Close the bleed valves and drain cock. Release the ball cock in the expansion tank and bleed the lower radiator levels. When you are done turn the boiler back on and relight it.