Which Adapter Do You Need for a Smart Thermostatic Radiator Valve
Smart thermostatic radiator valves (smart TRVs) are an increasingly popular way to upgrade home heating systems, offering remote control and improved energy efficiency. One important step when fitting a smart TRV is ensuring it is compatible with your existing radiator valve.
This guide covers the most common radiator valve types found in homes and the adapters and thread sizes required for each.
Why You May Need an Adapter
Smart Radiator Valves are usually designed to fit onto a standard M30 x 1.5mm threaded valve. If your valve is a different size or fitting style, you’ll probably need an adapter to bridge the difference.
IMPORTANT: If your radiator has a basic manual on \ off valve then it will very likely not be compatible with a smart Thermostatic Radiator Valve, even using an adapter. In this situation the manual valve will need to be replaced. Ideally with a M30 x 1.5mm valve
Table of Valve Types and Thread Sizes
| Valve Type | Thread Size | Common in UK? | Adapter Required? | Notes |
|---|---|---|---|---|
| M30 threaded | M30 x 1.5mm | Yes | No | Fits most smart TRVs directly |
| Danfoss RA | Push-fit | Yes | Yes | Requires Danfoss RA adapter |
| Danfoss RAV | 34mm base | Occasionally | Yes | Requires RAV adapter |
| Danfoss RAVL | M26 x 1.0mm | Occasionally | Yes | Requires RAVL adapter |
| Drayton TRV3/4 | Non-standard | Yes | Yes | Often needs a brand-specific adapter |
| Pegler Terrier | M28 x 1.5mm | Yes | Yes | Use M28 or universal adapter |
| Oventrop | M30 x 1.0mm | Rare | Yes | Finer thread – use brand adapter |
| Herz / Comap | M28 x 1.5mm | Occasionally | Yes | Universal adapter often works |
| Giacomini | Proprietary |
Common Radiator Valve Types in the UK (with Thread Sizes)
1. M30 x 1.5mm Threaded Valves
- Prevalence: Most common valve thread in modern UK and European homes
- Thread Size: M30 x 1.5mm (30mm diameter, 1.5mm thread pitch)
- Adapter Required: Probably not, this is the standard fitting for most smart TRVs
- Compatible: With most big brands like Moes, tado, Netatmo, Honeywell Evohome, Eve, etc.
2. Danfoss RA Valves
- Prevalence: Common in UK homes, especially in older systems
- Thread/Fitting: Push-fit, not threaded. Clips over valve body with a locking ring
Other Danfoss valve types:
- RAV: 34mm base, pin-operated. Requires RAV adapter
- RAVL: 26mm thread. Requires RAVL adapter
3. Drayton TRV3 / TRV4
- Prevalence: Most common in 1990s–2000s UK heating systems
- Thread Size: Non standard (not M30)
- Adapter: May accept a universal adapter with some smart TRVs
4. Pegler Terrier Valves
- Prevalence: Less frequently used in UK installations
- Thread Size: Commonly M28 x 1.5mm
- Adapter Required: Yes, M28 adapter or universal adapter
- Looks similar to M30 but won’t fit without adapter
5. Other European Valves (Heimeier, Oventrop, Comap, Herz, Giacomini)
- Prevalence: Less common in UK, sometimes used in imports
- Thread Sizes:
- Heimeier: M30 x 1.5mm (may be directly compatible)
- Oventrop: M30 x 1.0mm – requires specific adapter
- Herz / Comap: M28 x 1.5mm
- Giacomini: Often proprietary, may require clip on adapter
- Adapter Required: Yes, brand specific or universal kit
6. Manual Valves
Manual valves are not compatible with Smart Radiator Valve connectors. If you have a radiator where you have to manually turn in on \ off then the radiator has a manual valve.
Options:
Replace the manual valve with a TRV body
- This is the best solution.
- A plumber can swap the manual valve for a thermostatic one (usually M30 thread), which then accepts a TRV head, including smart TRVs.
- Not a big job for a professional plumber
Use an adapter kit (in rare cases)
- Some smart TRV kits include clip-on or compression-style adapters that can fit over certain manual valves.
- This is very hit and miss and depends on the brand and valve type.
- Even if it fits, control might be less accurate or reliable.
Upgrade to a full TRV
- Many people simply replace manual valves with new thermostatic ones, cheap and effective, and it opens up full compatibility with smart TRVs.
Universal Adapter Kits
Most smart TRV brands include a universal adapter kit containing:
- M28 x 1.5mm adapters
- Danfoss RA, RAV, RAVL adapters
- Clip-on or push-fit adapters
- Locking rings and collars
These kits usually cover most radiator types
How to Identify Your Valve and Thread Size
- Remove the existing TRV head to expose the valve body.
- Check if the valve is threaded or push-fit.
- Measure the diameter, 30mm = M30, 28mm = M28, etc.
- Use a thread gauge or trial fit adapter if unsure.
- Refer to a manufacturer’s compatibility list or consult a plumber.
Summary
Most UK radiators use the standard M30 x 1.5mm threaded valve. This connection type is the standard that virtually all smart radiator valves come with as standard. So, you probably won’t need an adapter. If you do need and adapter, they are straight forward to fit.
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