How to fit a smart radiator valve
Updated: October 2026
You are about to take the old head off a radiator and you want to know whether that is a ten-minute swap or a leak. This page is how to fit a smart radiator valve on a UK wet system when the body underneath is already a thermostatic radiator valve. If the pin springs back up after you lift the head, you can fit the new one. If water appears, or the body is a wheelhead, you stop. Prices and star ratings stay on the [smart radiator valve comparison](/hub/thermostats/smart-radiator-valve). The order of checks is on the [buying guide](/hub/thermostats/smart-radiator-valve/sub/smart-radiator-valve-buying-guide). Products Compared did not fit these heads in a lab. A qualifying purchase through our links can earn a commission at no extra cost to you.
You are about to take the old head off a radiator and you want to know whether that is a ten-minute swap or a leak.
You are about to take the old head off a radiator and you want to know whether that is a ten-minute swap or a leak. This page is how to fit a smart radiator valve on a UK wet system when the body underneath is already a thermostatic radiator valve. If the pin springs back up after you lift the head, you can fit the new one. If water appears, or the body is a wheelhead, you stop. Prices and star ratings stay on the smart radiator valve comparison. The order of checks is on the buying guide. Products Compared did not fit these heads in a lab. A qualifying purchase through our links can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Adaptors | Power | Hub | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Hive Hive smart radiator valve | M30 and Danfoss RA | 2 AA claimed; 9V field conflicts | Required, not included | 8.4 | about £55.30 | View offer |
 tado tado X starter kit with Bridge X | Adapter sets for both heads | Rechargeable, 2 included | Bridge X in the box | 8.4 | about £207.15 | View offer | |
| Preis-Tipp |  SONOFF SONOFF TRVZB Zigbee head | M30 × 1.5 mm plus named rings | 3 AA, not included | Zigbee coordinator required | 8.2 | about £22.30 | View offer |
On this page
Check the valve before you open anything
Turn the heating off and let the radiator go cool before you touch the head. A thermostatic body has a head that pushes a small pin. A manual wheelhead is a different object: it opens and closes the water, and Hive’s installation guide says that sort of valve needs a new body fitted by a heating professional. Electric radiators are out as well. Hive’s shop says its valve is not for electric heating. Look at the collar that will come off with the old head, and photograph it with any numbers you can see. M30 × 1.5 mm is the thread SONOFF claims, and it is the union many UK TRV heads use. Danfoss RA is a clip pattern, and both Hive and the Kasa KE100 pack an adaptor for it. M28 is the size Hive reviews say is not in the box. If you cannot name the collar from the photo, order nothing yet.
Swap the head
Set the old head to its highest number so the pin is not held down, then unscrew or unclip it. You should not have to drain the radiator for this, provided you are only changing the head on a standard TRV body. Guides for brass valve bodies are about replacing the body itself, which is a different job. Lift the head clear and press the pin gently. It should spring back up. A pin that stays down, or a body that weeps at the joint, is the moment to stop. Fit the adaptor ring that matches the photograph, then tighten the new head by hand until it sits square. Do not add force to close a gap: a gap means the adaptor is wrong. Pair the head in the app while you are still beside the radiator. tado, Hive, Kasa, and SONOFF each use their own app and their own hub, so follow the card in that box. If the app asks you to run the heating for calibration, turn the heating back on and leave it, because Hive reviewers describe calibration that needs a long period with the heating running. A schedule you set before that calibration finishes can look as if the valve has failed.
Adaptors in this comparison
Hive’s components line, on the about £55.30 head, lists an M30 adaptor and a Danfoss RA adaptor, plus two AA batteries. Ignore the separate field that says two 9V batteries. Reviews say an M28 adaptor is requested from Hive and is not in this carton, and one buyer waited up to two weeks. The Kasa KE100 add-on includes one RA adaptor, a cover opener, and two AA cells. Reviewers often needed nothing else, and some cross-threaded the plastic adaptor, so start it by hand. SONOFF claims M30 × 1.5 mm and lists adaptors marked CAL, RAVL, RAV, M28, and GIA. Three AA batteries are not in the box. The tado X starter includes adapter sets for its two heads. Both WILAWELS listings say complete accessories and most standard valves, and neither names a thread. One TRV601W review says the heads did not fit until an extra part was ordered. If your photo matches none of those names, the head on the best smart radiator valve page is still the wrong head until the adaptor exists. The KE100 three-pack listing does not list parts at all, so use the single-head listing if you need the adaptor named.
When you should stop
Stop when the pin does not spring, when the union weeps, or when the body is a wheelhead. Those are jobs for a heating engineer. The same stop applies once a valve is seized or you are replacing several bodies. Draining a system, altering boiler wiring, and opening a gas pipe are not part of a head swap. Gas work belongs to a Gas Safe engineer. A seized pin on a tado install in the reviews needed a plumber, which is the same stop. A head that pairs and then leaves the boiler running, or leaves the room cold, is a control problem rather than a tighter spanner. Closing the pin only closes that radiator. What asks the boiler to fire is on the boiler control page. Leave at least one path open if the circuit needs it, and do not shut every radiator in the house on the first evening.
Common questions
Do I have to drain the radiator to change the head?
You do not drain for a head swap on a standard thermostatic body, as long as you leave the brass body in place. Unscrew the old head, check the pin, and fit the new one. Draining starts when the body itself is coming off, when the joint weeps, or when the valve is seized. That is the point to call a heating engineer rather than to improvise a drain-down.
How do I know if I have M30 or Danfoss RA?
Photograph the collar before you buy. M30 × 1.5 mm is a threaded union, and it is the size SONOFF prints. Danfoss RA is the clip pattern that Hive and the KE100 pack an adaptor for. If the collar is marked M28, Hive’s box does not include that adaptor. If no marking is readable, treat the thread as unknown and match the photo to a named adaptor in the listing before you pay.
What if the pin does not spring up?
Leave the new head in the box. A pin that stays down will not let the radiator open and close, and forcing a smart head onto it does not free it. Work the pin by hand only if it moves. If it is stuck, or the body weeps when you touch it, a heating engineer needs to see the valve. One tado review ended at exactly that plumber visit.
Which adaptors are in the Hive, Kasa, SONOFF, and tado boxes?
Hive includes M30 and Danfoss RA. The KE100 add-on includes one RA adaptor. SONOFF includes adaptors marked CAL, RAVL, RAV, M28, and GIA, and claims M30 × 1.5 mm. The tado X starter includes adapter sets for two heads. WILAWELS says complete accessories and does not name a thread.
Can I fit this on a manual wheelhead?
You cannot treat a wheelhead as a TRV. Hive’s guide says a manual on/off valve needs a new thermostatic body, and that body is a job for a heating professional. The smart head has nothing to press until that body is there. Electric panel radiators are a separate exclusion on Hive’s shop page. Buy the head after the body is a TRV and the pin moves.
Why does the app ask me to run the heating for calibration?
The head learns the pin travel while hot water is actually moving. Hive reviews describe calibration that needs the heating left on for a long period, and a valve that is judged before that finishes can look faulty. Turn the heating on when the app asks, keep the radiator uncovered, and wait until the app says the step is done. A schedule set in the middle of that run is the usual reason the first evening looks wrong.
Related pages
Sources
Public UK sources for Boiler Plus in England and for room controls when a boiler is replaced. Listings are the amazon.co.uk captures for these seven ASINs on 16 October 2026, not a live reload. Prices on amazon.co.uk move. Manufacturer saving percentages are not a result from this comparison.
- Boiler Plus factsheet (retrieved 16 October 2026)
- Boiler Plus clarification (retrieved 16 October 2026)
- BEAMA Part L heating controls (retrieved 16 October 2026)
- BEAMA TRV installer factsheet (retrieved 16 October 2026)
- tado Bridge X (retrieved 16 October 2026)
- tado X and older lines (retrieved 16 October 2026)
- TP-Link KE100 FAQ (retrieved 16 October 2026)
- Hive radiator valves (retrieved 16 October 2026)