Fitting a radiator - a complete guide

Fitting a radiator is more straightforward than you think. It involves isolating the system, draining the radiator, removing the old radiator, mounting the new radiator, and reconnecting the water supply. 

It’s that simple. As far as intangibles, it's important to ensure proper bracket placement and alignment, and to check for leaks after reconnecting the water.

In this complete guide, we’ll take you through everything you need to know about fitting a radiator. From preparation and positioning to pipework and finishing touches, we’ll help ensure your installation goes smoothly and safely, whether you’re doing it yourself or hiring a professional.

Table of Contents

1. Why fit a new radiator?
2. How to fit a radiator yourself
• Step 1 - Planning and preparation
• Step 2 - Location, pipework and wall fixings
• Step 3 - Fitting the radiator
• Step 4 - Filling, bleeding and testing
• Common mistakes to avoid
3. Hiring a professional
4. Frequently asked questions (FAQs)
• Cost & budget
• DIY vs Professional
• Choosing a new radiator
• Installation & technical issues
• Specific situations
5. Stunning radiators at TradeRadiators.com

Why fit a new radiator?

Adding heat to a new room or extension

If you've built a new room, converted a loft or garage, or extended your home, it’s vital to ensure the space is adequately heated, particularly in the UK’s colder months. A well-sized radiator helps integrate the new area seamlessly into the rest of your home’s heating system, making it just as cosy and usable as any other room. Proper planning at this stage also helps avoid future issues like uneven heat distribution or unnecessary strain on your boiler.

• Further reading: Choosing The Right Type of Radiator

Replacing a removed or faulty radiator

Sometimes radiators need to be removed due to decorating, renovation work, or because they’ve become inefficient or damaged. If your old radiator was leaking, rusting, or simply not providing enough warmth, replacing it is often the simplest solution. Fitting a new radiator in its place ensures your heating system remains effective and balanced, and modern radiators can often outperform older ones in terms of heat output and efficiency.

• Further reading: Replacing a Radiator - A Complete Guide

Improving your heating system’s efficiency

Upgrading to a more modern radiator can make a noticeable difference to how quickly and evenly your home warms up. Older radiators may be full of sludge or air, reducing their output. Newer designs often feature better construction, more responsive controls, and improved heat transfer, especially when paired with thermostatic radiator valves (TRVs). Fitting a new radiator can be a cost-effective way to boost your energy efficiency without overhauling your entire system.

• Further reading: How to Flush Sludge Out of Your Radiator

Updating the look or layout of a room

Radiators aren't just functional, they’re an important part of your décor. If you're redecorating or redesigning a space, the existing radiator may look out of place or be awkwardly located. Installing a radiator that better suits the layout, size, or style of your room can enhance both comfort and aesthetics. Vertical and designer radiators, for example, are increasingly popular choices in modern interiors for their space-saving and visual appeal.

• Further reading: Where Should I Be Putting My Radiator?

How to fit a radiator yourself

If you’re confident in your DIY abilities and have a decent grasp of basic plumbing, fitting a radiator yourself can be a rewarding project, and one that could save you a significant amount of money by avoiding the cost of hiring a professional (which we’ll cover later in the article). That said, this is not a job to take on if you’re unsure about what you’re doing or if your setup is particularly complex, such as installing in a new location or dealing with unusual pipework. In those cases, it’s always safest to call in an experienced heating engineer.

Step 1 - Planning and preparation

Assess your heating needs

Before anything else, calculate how much heat output (BTUs) the room will need. This depends on:

• Room size (length x width x height)
• Number and size of windows
• Room insulation and draft-proofing
• Type of space (kitchen, bedroom, bathroom, etc.)

Use our BTU Heating Calculator to make this step simple. It ensures that the radiator you choose will be powerful enough to heat the room effectively, without being overkill.

Choosing the right radiator

Once you know your BTU requirements, you can pick the radiator that suits both your practical needs and your interior aesthetic. Radiators come in a wide range of styles:

• Panel radiators for standard performance
• Column or cast iron models for period charm and heat retention
• Vertical radiators for small or narrow spaces
• Designer and feature radiators for stylish modern interiors

Be sure to match the radiator's pipe centres with your existing pipework if you’re connecting to it directly. This will save a lot of hassle later.

Tools you'll need

• New radiator, with wall brackets
• Radiator valves (manual or thermostatic)
• PTFE tape or jointing compound
• Adjustable spanners or wrenches
• Pipe cutter and pipe bender (if new pipework is needed)
• Drill and appropriate wall plugs
• Measuring tape and spirit level
• Radiator key
• Bucket and towels
• Central heating inhibitor (recommended for system longevity)
• Gloves and safety glasses

Step 2 - Location, pipework and wall fixings

Positioning the radiator

The most common place to install a radiator is under a window. This allows the radiator to counteract the cold air coming through the glass, improving heat distribution in the room. However, modern insulation has made other locations viable, so long as the radiator is positioned where air can circulate around it.

Avoid placing radiators behind furniture or heavy curtains, as this can block the heat and make your system less efficient.

• Further reading: What You Should Never Put Near a Radiator

Checking & adjusting pipework

If you’re replacing a radiator in the same spot, the existing pipework may align perfectly. But if you’re fitting a radiator in a new location or switching to a different size, you might need to reroute or extend the pipes.

This could mean:

• Cutting into existing pipes
• Using compression fittings or solder joints to extend runs
• Securing new pipework through floors or walls

Plastic piping can make this process easier in tight spaces, but copper remains the most durable and preferred choice for many DIYers and professionals.

• Further reading: Learn How To Pipe a Radiator (Video)

Step 3 - Fitting the radiator

Once your pipework is in place and the wall is ready, it’s time to hang your new radiator. Accuracy and care at this stage will ensure the radiator is secure, level, and works efficiently.

Mounting the brackets

• Mark bracket positions carefully
  Use your radiator’s bracket template (or measure the back of the radiator if there isn’t one) to mark where the wall brackets will go. Double-check that these align with your pipe centres and allow space for the valves to be fitted comfortably.
• Drill and fix the brackets
  Use a spirit level to make sure your marks are level before drilling. If you're mounting onto plasterboard, make sure you use suitable wall plugs or fixings designed for cavity walls. For masonry walls, standard wall plugs and screws will do. The radiator will be heavy, especially cast iron ones, so use strong fixings appropriate for the wall type.
• Hang the radiator on the brackets
  With the brackets securely in place, carefully lift the radiator and hook it into position. You may need someone to help you with this step, particularly with heavier radiators, to avoid any damage or injury. Check again that it’s level before proceeding.
• Ensure clearance from the wall and floor
  There should be a small gap between the back of the radiator and the wall, and also between the radiator and the floor. This allows for heat circulation and easy cleaning. Use manufacturer guidelines or existing radiator measurements as a reference.
• Further reading: How to Fit a Vertical Radiator (Video)

Attaching the valves

• Fit the radiator valves to the radiator
  Wrap PTFE tape around the valve tails (about 5–10 turns), then screw them into the bottom inlets of the radiator. Tighten with a spanner, but don’t overdo it. Cast iron radiators especially can be damaged with excessive force.
• Connect valves to pipework
  Position your valves in line with the copper pipework or flexible tails. Compression fittings are most common, ensure the olives and nuts are in place before tightening. A pair of adjustable spanners can help here with one to hold the valve body and one to tighten the nut.
• Double-check all connections
  Before refilling your system, go over every joint and fitting. Look out for misalignment, loose fittings, or anything that looks like it could cause a leak once water is flowing.
• Attach any additional fittings
  Now is the time to add things like decorative pipe covers or caps if you’re using them. Also, check that the air vent (bleed valve) is tightened, but still accessible for later.
• Further reading: How to Replace a Radiator Valve

Once the radiator is mounted and connected, you're ready to move on to the next stage, which is testing for leaks and bleeding the system.

Step 4 - Filling, bleeding and testing

Now that your radiator is in place and the valves are connected, it's time to fill the system, remove any trapped air, and check everything’s working as it should. Taking your time with this step will help avoid leaks and ensure efficient heating.

Reopen your system and refill with water

Start by making sure both radiator valves are open (turn them anticlockwise). If you've drained your central heating system, you’ll now need to refill it. For combi boilers, this usually means using the filling loop to bring the pressure back up to the correct level (typically 1.0–1.5 bar, but check your boiler manual).

If you're working on a sealed system, make sure all bleed valves in other radiators are closed before refilling. You may hear water flowing back into the system which is normal. Keep an eye on the pressure gauge as you fill.

• Further reading: How to Refill a Central Heating System Efficiently

Bleed the radiator

Once full, air pockets may still be trapped inside the radiator. These will prevent it from heating up evenly. Using a radiator key, slowly open the bleed valve at the top side of the radiator. You should hear a hissing sound as air escapes.

Once water begins to trickle out steadily, close the valve tightly. Always bleed your radiator with the heating system off to avoid hot water spraying out. You may need to top up the boiler pressure again afterwards if it drops.

• Further reading: How to Bleed a Radiator - A Complete Guide

Check for leaks

With the system bled and repressurised, turn your heating back on. Allow the system to run for 10–15 minutes. Carefully inspect all joints, valve connections, and the radiator itself for any signs of leakage. Use a tissue or dry cloth to detect small drips.

If you spot a leak, switch off the heating and retighten the fittings slightly. If problems persist, it might be worth draining the radiator again and resealing the connection with PTFE tape or jointing compound.

• Further reading: How to Fix a Pinhole Leak in Your Radiator or Pipes

Test for even heating

Once the radiator is up to temperature, feel across its surface to check for cold spots, especially at the top corners. If it still feels cold at the top, it may need to be bled again. The radiator should heat evenly from the bottom up.

Also, check that the thermostatic or manual valve is operating correctly and that the radiator responds when you turn it up or down. If the radiator stays cold while others heat up, it might be an issue with the valve or trapped air further in the system.

• Further reading: Why is My Radiator Cold at the Top/Bottom?

By the end of this step, your radiator should be securely installed, leak-free, and heating efficiently, ready to keep your room warm and comfortable. 

Common mistakes to avoid

Even if you're confident with DIY tasks, it's easy to overlook some crucial details when installing a radiator. Here are some of the most common pitfalls and how to avoid them:

Misjudging radiator size

Choosing a radiator that's too small for your room will mean it struggles to heat the space effectively. On the other hand, a radiator that's too large may cause the room to overheat and waste energy. Use a BTU (British Thermal Unit) calculator to determine the right size based on your room’s dimensions, insulation levels, and number of windows. Getting this right from the outset saves money and ensures your comfort.

Poorly positioned brackets

Incorrect bracket placement can cause your radiator to hang unevenly, or worse come loose from the wall over time. It’s essential to take your time when marking out where your brackets will go, ensuring they’re level and at the correct height. Use a spirit level and double-check your measurements. Also, make sure you're securing the brackets into solid wall material, using appropriate wall plugs and fixings.

Forgetting to use PTFE tape

PTFE (Polytetrafluoroethylene) tape is essential when connecting valves to prevent leaks at the threaded joints. Skipping this step, or not applying enough tape, can lead to slow drips that may not be obvious straight away, but could damage your flooring or plasterwork over time. Wrap the tape around the threads in the direction of tightening (clockwise), and ensure it's snug and smooth.

Over-tightening connections

While it might feel reassuring to really crank everything tight, over-tightening joints and fittings can crack valve bodies or distort threads, leading to leaks or broken parts. Tighten firmly, but not excessively. If you're unsure, stop when resistance is felt and test for leaks after turning the system back on. It’s always easier to tighten a little more later than to fix something that’s been overtightened and broken.

Not bleeding the radiator properly

Air trapped inside your new radiator can stop it from heating efficiently. Some people forget this step entirely, or don’t bleed the radiator thoroughly. Always bleed your radiator once it’s full of water and again after the heating has been running for a short while. Use a radiator key, and keep a cloth handy to catch any drips. Bleeding ensures the whole surface heats up evenly and maximises efficiency.

By being mindful of these common mistakes, you'll give yourself the best chance of a smooth, successful installation and a warm, evenly heated room.

Hiring a professional

While fitting a new radiator is something many confident DIYers can manage, especially if it's a straightforward swap, there are times when bringing in a Gas Safe Registered professional is absolutely the right call.

If you're not confident working with plumbing, or if your installation involves new pipework, repositioning the radiator, or integrating it into an existing heating system, it's wise to hire a qualified plumber or heating engineer. A professional will ensure everything is installed correctly and safely, helping you avoid leaks, inefficient pipework layouts, or damage to your boiler system.

Installing multiple radiators, especially in older properties, often involves more complex planning and pipe rerouting. In these situations, experience matters. A seasoned professional will not only handle the practical side of things but may also suggest smarter layout choices you might not have considered. If your central heating system hasn't been touched in years, they can also check the boiler to ensure it's still up to the job, particularly if you're adding more radiators to the system.

Here’s a rough guide to labour costs for professional radiator installation, courtesy of Checkatrade:

These are average labour costs and don’t include the cost of the radiator itself. Rates may also vary depending on your location, for example, expect higher charges in London compared to, say, Carlisle.

For electric radiators, always use a qualified electrician. These must be installed in accordance with legal safety regulations and are not considered a DIY job.

Some tradespeople are happy to supply and fit a radiator of their choice, which might suit you fine if your priority is functionality over design. But if you have a specific radiator style, finish or brand in mind, like a sleek vertical model or a classic cast iron column radiator, it's often best to source it yourself and simply pay a professional for installation. That way, you get the look you want, at a price you’ve chosen, with the peace of mind that it’s been fitted properly. Make sure you use our Heating Calculator to input your room's dimensions so that you know what size and heat output you need from your radiator to comfortably heat the room.

• Further reading: What is the Cost of a New Radiator?

Frequently asked questions (FAQs)

Cost and Budget

DIY vs Professional

Choosing a New Radiator

Installation and Technical Issues

Specific Situations

Stunning radiators at TradeRadiators.com

If you’d prefer to choose a radiator that matches your personal style rather than relying on a tradesperson’s default choice, be sure to explore the exceptional range available at Trade Radiators.

As the UK’s largest independent retailer of radiators, heated towel rails and electric heating solutions, Trade Radiators has built a reputation for quality, value, and unbeatable variety. From sleek designer radiators to compact panel models and stylish accessories, there’s something for every room and budget.

With competitive trade prices, free delivery across mainland UK, and next working day delivery available on most radiators, getting the perfect heating solution has never been quicker or easier. Find exactly what you need, when you need it – only at Trade Radiators.

For additional inspiration, we've included some amazing photos from our customers who have kindly taken photos of their beautiful radiators installed in their homes. Hopefully this can give you an idea of the types of new radiator you can put in your living space!