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 better 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 the UK 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 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 homes
Thread Size: M30 x 1.5mm (30mm diameter, 1.5mm thread pitch)
Adapter Required: No – this is the standard fitting for most smart TRVs
Notes: Compatible with 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
Notes: 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: Common in 1990s–2000s UK heating systems
Thread Size: Non-standard (not M30)
Notes: May accept universal adapter with some smart TRVs

4. Pegler Terrier Valves

Prevalence: Frequently used in UK installations
Thread Size: Commonly M28 x 1.5mm
Adapter Required: Yes – M28 adapter or universal adapter
Notes: 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

Your 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 if you’re already draining the system.

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 used in the UK.

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.
RareYesClip-on adapter required

Summary

Most UK radiators use the standard M30 x 1.5mm threaded valve. This is connection type is the standard that virtually all smart radiator valves come with standard. So, you probably won’t need an adapter. If you do need and adapter, they are straight forward to fit.