Replacement TRV Heads – Fix Your Radiator Controls
If your radiator dial is cracked, yellowed, or no longer turning, a replacement Thermostatic Radiator Valve (TRV) head is a quick and cheap fix. However, before you buy, it is essential to check if your valve body is compatible.
Universal UK Fitment: M30 x 1.5
The majority of modern UK radiators use an M30 x 1.5mm threaded connection. This is the industry standard for brands like Honeywell, Myson, and many generic UK retailers.
- Easy Swap: Only replace the plastic head, leaving the wet plumbing intact.
- Energy Efficient: New liquid-filled sensors react faster to room temperature changes.
⚠️ Important Compatibility Notice
While M30 x 1.5 is the "standard," not all radiator heads are the same. Your replacement depends entirely on the brand and model of the valve body already installed on your pipes:
- Drayton Valves: Often use a specific "click-fit" or unique thread that won't accept universal heads.
- Old Valves: Systems over 20 years old may use imperial threads or discontinued snap-on designs.
- Brand Lock-in: Some premium brands (like Danfoss or Giaco) require their own proprietary replacement heads.
How to Identify Your Thread Size
Before ordering, inspect the base of your current radiator valve. Here is how to tell them apart:
Top Replacement TRV Heads in the UK
| Retailer | Stock Status | Model | Link |
|---|---|---|---|
| Screwfix | In Stock | Drayton RT212 | View Part |
| Toolstation | Available | Classic Thermostatic | Check Price |
| Ebay | Available | Universal M30 | Check Price |
Step-by-Step: How to Replace Your TRV Head
Replacing a TRV head is a 5-minute job that requires no plumbing experience. Follow these steps to ensure a perfect fit without causing a leak.
1. Identify Your Existing Brand
Before buying a replacement, look at the top or side of your current plastic dial. If you see names like Drayton, Danfoss, Honeywell, or Pegler, it is best to buy the same brand. While M30 x 1.5mm is "universal," some brands use a unique "click-lock" system rather than a screw thread.
2. Set the Dial to Maximum (Setting 5)
Turn the old head all the way to the highest number (usually 5 or the 'MAX' symbol). This is a crucial step—it retracts the internal plunger, removing pressure from the valve and making the head much easier to unscrew by hand.
3. Remove the Old Head
Locate the knurled metal ring at the very base of the plastic head (where it meets the metal pipe). Turn this ring anti-clockwise.
Tip: If it’s too tight for your fingers, use a pair of adjustable grips gently—don't apply too much force or you may crush the ring.
4. Inspect and "Exercise" the Pin
Once the head is off, you will see a small metal pin sticking up from the brass valve. Push it down with the flat side of a screwdriver. It should spring back up smoothly. If it doesn't move, gently tap the side of the brass valve with a tool handle until it pops up. This ensures your new head actually works once installed.
5. Fit the New Replacement Head
Ensure your new head is also set to '5'. Align it squarely over the valve and push down firmly. Thread the metal ring clockwise onto the valve base. Hand-tighten only—using tools to tighten the ring can snap the plastic internal components of the new head.
💡 Pro Tip: Stuck Pins
If your radiator is cold, it might not be the head at all. Remove the head and check the small metal pin on the valve. If it doesn't move when pressed, it's stuck. See our radiator troubleshooting guide for the fix.