How to change a TRV radiator valve: step-by-step guide
From faulty TRVs to smart upgrades: everything installers need to know
Thermostatic Radiator Valves (TRVs) play a central role in modern heating systems. They allow each room to be adjusted independently, improving comfort and helping optimise energy use, but they are only one part of the bigger picture of home heating control.
For a full overview of thermostat types and how they work, see our complete guide to thermostats
[Table of Contents]
- When does a TRV radiator valve need replacement?
- Tools and materials required
- How to change a TRV radiator valve (step-by-step)
- Testing and commissioning the system
- Common mistakes to avoid
- Recommending smart TRVs to your customers
- Why TRV replacement is a growth opportunity for installers
When does a TRV radiator valve need replacement?
Knowing when a TRV should be replaced helps installers avoid inefficiencies and customer complaints. Valves deteriorate with time, and in some cases, older models are incompatible with newer control systems. Identifying malfunction signs early also allows installers to position upgrades as a long-term comfort solution.
Signs of TRV malfunction
Over time, TRVs can become stuck, clogged with limescale or simply wear out. Typical signs of malfunction include:
- radiators that remain cold even when the heating is on.
- valves stuck in fully open or closed positions.
- inconsistent heating across different rooms.
- unusual noises in radiators caused by poor flow regulation.
For installers, these are red flags that indicate the TRV is no longer functioning properly.
Age and compatibility issues
Even if a TRV still works, devices installed more than 15 years ago are often inefficient compared with modern equivalents. They may also be incompatible with today’s digital thermostats or zoning systems. Replacing old TRVs during boiler swaps or heat pump installations ensures better performance and avoids costly call-backs.
When to recommend a smart TRV upgrade
Smart TRVs, such as Resideo HR92, allow homeowners to schedule individual room heating and control settings remotely. With regulations moving towards mandatory programmable TRVs, recommending these solutions today demonstrates forward-thinking expertise. Installers can explain to customers that an upgrade will not only improve comfort but also future-proof their home against regulatory changes.
Tools and materials required
Having the right tools ready before starting work is essential for efficiency and safety. Installers should also make sure customers understand that some water spillage is normal and system downtime is temporary during replacement.
Safety first: what to do before replacing
Safety and preparation are essential. Installers should always:
- switch off the boiler and allow the system to cool.
- isolate the radiator by closing both the existing TRV and the lockshield valve.
- place absorbent cloths or trays under the radiator to catch any water.
- brief the customer about potential minor water spillage and system downtime.
Tools checklist
A typical TRV replacement requires:- adjustable spanners and grips.
- PTFE tape for sealing threads.
- radiator bleed key.
- bucket or trays for draining.
- towels or protective sheets.
- replacement TRV kit (valve body and head).
Having everything ready reduces installation time and prevents delays on-site.
Choosing the right TRV for the system
Selecting the correct TRV is about more than size. Installers should check:
- pipe dimensions (usually 15mm or 22mm in the UK).
- system pressure rating.
- orientation (angled, straight or corner valves depending on pipework layout).
- smart compatibility if upgrading (e.g., integration with evohome).
A poor match can lead to leaks, poor regulation or future call-backs.
How to change a TRV radiator valve (step-by-step)
Replacing a TRV follows a clear procedure that reduces errors and ensures a professional job. By following step-by-step instructions carefully, installers ensure the new valve operates smoothly and efficiently.
Remove the old TRV head and valve body
- Unscrew and remove the TRV head.
- Use a spanner to disconnect the valve body from both the radiator and pipe.
- Allow residual water to drain into a tray.
At this stage, installers should check the radiator tail for corrosion or wear – if damaged, it should be replaced.
Fit the new TRV body
- Apply PTFE tape to the threads to ensure a watertight seal.
- Position the new TRV body carefully, ensuring the flow direction matches system requirements (often marked with an arrow).
- Tighten securely but avoid over-tightening, which can distort fittings.
Install and calibrate the TRV head
Once the body is installed:
- Attach the TRV head, ensuring it aligns correctly with the spindle.
- For smart TRVs, follow the pairing process with the central controller (e.g., evohome) and carry out calibration.
- Check manufacturer documentation for specific setup steps.
Testing and commissioning the system
Once the new TRV is installed, testing is critical to confirm correct operation. This step helps avoid customer complaints and ensures that the system runs smoothly after the intervention.
Refill radiator and check for leaks
Open the lockshield and TRV, allow the radiator to refill, and bleed excess air with a bleed key. Carefully check for leaks at all joints.
Test TRV function at different settings
Adjust the TRV through its full range to ensure smooth movement and accurate temperature response.
Check full system balance (optional)
Whenever multiple TRVs are replaced, system balancing should be verified. This ensures even heat distribution and prevents boiler cycling. Installers who include this step often gain customer trust by delivering superior performance. They can find the right presetting of radiator valves with Honeywell Home TRV Balancing App.
Common mistakes to avoid
Mistakes in TRV replacement often cause unnecessary callbacks. Avoiding these common errors saves time, reduces costs and improves customer confidence in the installer’s professionalism.
Not isolating the system properly
Mistakes in TRV replacement often cause unnecessary callbacks. Avoiding these common errors saves time, reduces costs and improves customer confidence in the installer’s professionalism. Failing to close both valves can lead to unnecessary water loss, a mess and customer dissatisfaction.
Over-tightening fittings
While leaks are a concern, overtightening can cause thread damage or hairline cracks, resulting in later leaks that require another visit.
Incompatible TRV head or valve body
Mixing brands or models can lead to poor performance or calibration issues. Always verify that TRV components are compatible before fitting.
Forgetting the customer demonstration
Many call-backs happen because customers are unsure how to use new TRVs. Installers should always explain the operation clearly, especially when fitting smart models.
Unbalanced system
A central heating system doesn't distribute hot water evenly, leading to inconsistent room temperatures, cold radiators, and potential increased energy bills.
Recommending smart TRVs to your customers
Smart TRVs are in increasing demand due to their programmability and remote control capabilities. Installers can use replacement opportunities to position smart devices as a natural upgrade, especially with regulations requiring programmable TRVs by 2027.
When a smart upgrade makes sense
Installers should consider recommending smart TRVs in situations such as:
- customers wanting app-based or remote control.
- homes with variable occupancy (e.g., spare rooms or home offices).
- systems already equipped with a smart thermostat.
Resideo solutions: evohome and HR92
The HR92 smart TRV, when combined with evohome, allows full multizone control. Each room can be scheduled independently, offering customers both comfort and flexibility. This also helps installers stand out by offering premium solutions.
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Support, documentation and installer training
Resideo provides extensive resources, from product datasheets to installation guides, plus dedicated training through the Resideo Academy. Installers can reduce errors and grow their expertise with these resources.
Why TRV replacement is a growth opportunity for installers
Replacing a TRV is more than a maintenance job – it is a chance to strengthen customer relationships, reduce failure costs, and open discussions about system upgrades. By recommending smart TRVs, installers not only meet immediate needs but also prepare customers for future regulations and improved comfort.
The process is straightforward, but when done with care, professionalism and attention to detail, it can showcase the installer’s expertise and reliability. Customers remember the installer who not only fixed a problem but also improved their home’s comfort and future-proofed their heating system.
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