How To Fit Replacement Radiator Caps

Before you order Radcaps...

Radcaps universal replacement radiator caps fit most central heating valves but it's worth checking before you order.

Our replacement radiator caps will fit on a valve spindle up to 8mm x 5mm so please measure and check you have a standard valve/spindle as pictured on the right. If you're unsure why not contact us and send a photo and the dimensions of your valve, we also have an online chat facility (look for 'How can we help?' in the bottom right of this window).

How to measure a radiator valve

A standard radiator generally has two valve types called Lockhead and Wheelhead valves, Radcaps fit both valve types.

To determine which is which on your radiator turn off your central heating so the radiator goes cold. Then switch the heating back on and whichever pipe gets hot first is the Wheelhead valve.

  • The Wheelhead valve is for turning the radiator on/off.
  • The Lockshield valve is for regulating the amount of water that passes through the radiator. They are not required for manual control and should be left in the pre-set position.

As long as your spindle looks similar to the photo (on right) and the spindle isn't bigger than 8mm x 5mm then RADCAPS will fit.

correct size valve for Radcaps
How to buy radiator caps

It's easy to order...

Simply visit our online shop, select the number of caps you need (normally 2 per radiator) place your order and we will send you the caps 2nd Class Royal Mail*...the pack includes Radcaps, instructions and a hex key to install.


*Royal Mail Recorded Delivery optional.

Step 1.

Place the new replacement radiator cap over your radiator valve.

installing a radiator cap
how to push install radiator cap onto valve

Step 2.

Push the Radcap over the valve so that it sits nice and straight.

Step 3.

Locate the small hole on the side of the Radcap, insert the provided Hex Key and tighten until the cap is firmly secure.

tighten radiator cap
white plastic cap on radiator valve

Step 4. might also want to check out our other products Pipe Collars and Pipe Sleeves to further improve the look of your radiators.