How to Fit a Radiator: Complete Installation Guide

Adding or Replacing a Radiator

Whether you're adding a radiator to a cold room or replacing an old one, the process is straightforward if you understand the steps. This guide covers both standard replacements and new installations.

Before You Start: Planning

Sizing your radiator:

• Calculate room heat loss (BTU calculators available online)
• Choose radiator output to match or slightly exceed requirement
• Consider: room size, insulation, window area, external walls
• Bigger isn't always better - oversized radiators short-cycle

Position considerations:

• Under windows is traditional (counteracts cold downdraft)
• External walls most effective
• Need access to pipework below floor or from walls
• Allow clearance above and below for airflow

Tools You'll Need

• Pipe slice or pipe cutter
• Adjustable spanners (two needed)
• Drill and bits for wall fixings
• Spirit level
• Tape measure
• PTFE tape
• Pipe bender or fittings
• Bucket and towels
• Radiator key

Removing an Old Radiator

1. Turn off the heating - let system cool
2. Close both valves:
   • Lockshield valve (the one with the cap) - note the turns to close
   • TRV or manual valve on the other end
3. Place bucket and towels below connections
4. Open bleed valve - breaks vacuum, lets water flow out
5. Undo valve union nuts - use two spanners (one to hold valve, one to turn nut)
6. Lift radiator off brackets - tip to drain remaining water into bucket
7. Cap or plug the valve tails - prevents drips

Fitting the New Radiator

If same size/position:

1. Fit valve tails to new radiator (use PTFE tape)
2. Hang on existing brackets
3. Connect to existing valves
4. Open valves and bleed

If different size:

1. Mark new bracket positions using radiator
2. Check level
3. Drill and fix new brackets
4. May need to extend or modify pipework

New Radiator Installation (From Scratch)

Step 1: Position and bracket:

1. Hold radiator in position, mark bracket locations
2. Check level carefully
3. Drill and plug wall
4. Fix brackets securely - radiators are heavy when full

Step 2: Pipework:

1. Identify nearest point to tap into existing system
2. Drain system down to below connection point
3. Cut into existing pipework and fit tees
4. Run pipes to radiator position
5. Use clips to secure pipework
6. Fit valves - lockshield one side, TRV or manual other side

Step 3: Connection:

1. Fit valve tails to radiator with PTFE tape
2. Hang radiator on brackets
3. Connect to valves - don't overtighten
4. Fit bleed valve and blanking plug

Filling and Bleeding

1. Close bleed valves on all radiators
2. Refill system via filling loop
3. Watch pressure gauge - typically 1-1.5 bar
4. Bleed radiators starting from lowest, working up
5. Top up pressure after bleeding
6. Check for leaks at all connections
7. Turn heating on and check radiator heats evenly

Setting the Lockshield Valve

The lockshield valve balances the system:

• If noted turns when removing old radiator, set to same
• If new installation, start fully open
• Balance system once running (radiators near boiler may need restricting)
• Lockshield adjustment affects heat distribution throughout house

Common Problems

Radiator cold at top:

• Air trapped - bleed it

Radiator cold at bottom:

• Sludge buildup - may need flushing

Leaking connections:

• Nip up union nuts gently
• Check PTFE tape on tails
• May need to remake connection

The Bottom Line

Radiator fitting is within the capability of competent DIYers and is bread-and-butter work for plumbers. The key is proper planning, careful valve management, and thorough bleeding afterward. Always respect the system - water damage from mistakes is expensive.

Check our hand tools for pipe cutters, spanners, and other plumbing essentials.