How to Fit a New Radiator — UK Step-by-Step
Fitting a new radiator is 2 hours with the right prep. Here is the trade method including drain-down, bracket install, pipe connection.
Step-by-step method
1. Drain the system
Turn off boiler. Attach hose to lowest drain-off cock. Open bleed screws on top-floor radiators to let air in.
2. Mark bracket positions
Radiator centreline. Brackets on the back. Level with a spirit level, mark drill holes.
3. Drill and fix brackets
Wall plugs and coach screws for masonry, toggle bolts for plasterboard with stud fix ideal.
4. Fit tails, TRV and lockshield
PTFE + Loctite 55 on tails, torque snug. Install TRV on flow, lockshield on return (or per install spec).
5. Connect and refill
Push copper pipes up to valves, compression joints tightened. Close drain-off, open bleed screws until water runs, top up pressure to 1.2 bar.
6. Balance the radiator
Open lockshield 2 turns as starting point. Adjust after 30 minutes running — return should be 10–15°C cooler than flow.
Frequently asked questions
Can I add a radiator without draining the whole system?+
For a completely new radiator with new pipe runs, freeze plugs can save partial drain. But most installs need drain-down.
How do I balance radiators after adding one?+
Close lockshields on rads closest to boiler slightly, open the new/far rad's lockshield more. Aim for equal return temp across all rads.