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How do I use my filling loop?

If your boiler pressure is down you may be asking how do I use my filling loop?

What is a filling loop for?

A filling loop is used to increase the pressure in your heating system.

It does this by connecting the heating system to the mains cold water pipework.

The pressure should be increased (topped up) to between 1 and 1.5 bar.

Some heating systems don’t have a filling loop. If there is no filling loop there will be a feed tank at a high point in your property. Usually in the loft or an airing cupboard.

What is a filling loop?

A filling loop normally consists of one or two valves and a pipe to connect them together. Some boilers have lever operated valves to fill the pressure.

Are the filling loop valves open or closed?

You can tell if the valve is open or closed by looking at the handle.

The handle on the valve is either in line with the body of the valve or across the body.

The valve is open if the handle is in line with the body.

The valve is closed if the handle is across the body.

How do I use my filling loop?

Filling loop with one valve

  • Slowly open the valve until you can hear the water flowing.
  • The reading on the pressure gauge will slowly rise.
  • When the pressure gets to between 1 and 1.5 turn off the valve.

Filling loop with two valves.

  • Check to see if the valves are open or closed. Sometimes one valve is left open for convenience.
  • Fully open one valve. (This may already be open).
  • Slowly open the other valve until you can hear water flowing.
  • When the pressure gets to between 1 and 1.5 turn off the valve.

Worcester filling loop with a key

Worcester have a long standing tradition of using the most user unfriendly technique for refilling the pressure.

  • A white plastic key is inserted into the filling loop and twisted into the locked position.
  • The water is slowly turned on using the square plastic knob.
  • When the pressure gets to between 1 and 1.5 turn the water back off again.
  • The white plastic key is twisted to the unlocked position and removed. There is always a little splash of water when the key is removed.
Worcester key operated filling valve.

Lever operated filling valve.

Each manufacturer has a different type of lever operated valve. However they are designed to be easy to use compared to traditional filling loops.

Worcester lever operated filling valve

When the pressure is below 1bar use the filling loop to top it up.

  • Pull the lever gently down.
  • You will hear water flowing .
  • The pressure gauge will rise (slowly).
  • When the pressure gauge gets to between 1 and 1.5 bar release the lever to stop the flow of water.

The boiler should now operate properly.

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