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New boiler, new radiators? The pros & cons of updating your whole heating system

The benefits of a full heating system upgrade

So, you’ve decided the time has come to finally replace your old boiler and give a much-needed upgrade to your heating system. The next question is, should you overhaul the whole central heating system and replace your radiators too, while you’re at it?

In this article, we’ll look at the pros and cons of replacing the whole heating system and whether it’s necessary.

Read on to find out more…


If you’ve decided to buy a new boiler and upgrade your heating system, it would make sense to consider replacing your radiators at the same time as it would mean less disruption and cost than replacing them both separately. Let’s take a look at some of the reasons why replacing your radiators along with your boiler makes sense.

A modern Milano designer radiator


You may think all radiators are born equal, but you’d be wrong. Radiator performance has improved a huge amount in response to quality and performance regulations.

In fact, modern radiators can be up to 50% more efficient than their year 2000 counterparts. This increased efficiency leads to a decrease in energy bills, meaning that your new radiators will eventually pay for themselves.

Modern radiators also channel water more efficiently, with hot water coming into contact with more radiator surface space, whilst using much less water.

To ensure you have the correct size radiator to heat your room efficiently, you can use a BTU calculator (British Thermal Unit) and take the guesswork out of the equation.


Over time the metal pipes and radiators in your heating system can rust, this rust is collected by the water running through your system and returned to the boiler where it can collect. This collection of debris is called ‘sludge’ and it’s a good reason to replace old radiators.

Sludge can build up in old radiators and stop them from heating to full capacity. Powerflushing can sometimes remove sludge build up but starting from £500 it’s a costly treatment without a guaranteed end result. Sludge formation will begin to build up again after the powerflush as there will still be corrosion occurring in your old radiators.

System filters can be fitted to the return pipes on your boiler, which collect sludge as it passes through using powerful magnets. This can cost anything between £150-£200 for the filter and installation. Many boiler manufacturers offer an additional warranty period if you install their system filter with your new boiler.

a picture of fingers holding a pipe that is filled with sludge and sediment


Gone are the days of radiators being a purely functional part of the home aesthetic. Modern radiators can be a focal point of a stylish room, with a wider range of styles and sizes than ever before. If you’re updating your boiler then not only can you increase the efficiency with a new radiator but you can also improve your home decor with a designer radiator.

A Milano Aruba anthracite radiator on a white wall.

Paint your old rads

You could always give your old radiators a lick of paint to freshen things up but that won’t improve their efficiency, if anything a few coats of gloss will mean it will take slightly longer to heat your room.

However, modern radiators only heat by radiation up to 20%, most of the heat given off by radiators is through convection; heated air around the radiator rises and cold air is drawn into and through the radiator from underneath.

If you have an older radiator, it may be partially corroded inside, adding sludge to your system. So while a freshly painted radiator may look nice on the outside, it may be a different story on the inside.

Thermostatic radiator valves

If you are looking to make your system as efficient as possible then you may also want to consider adding thermostatic radiator valves into the mix.

Thermostatic radiator valves have a dial allowing you to control the temperature of each individual radiator in your home. Smart thermostatic radiator valves will monitor your activity in each room and heat them accordingly, you can also programme them from your smartphone.

If you’re thinking about installing new radiators then it would make sense to add thermostatic radiator valves too.

A white Milano Alpha designer radiator with thermostatic valves.

Cost implications

Replacing a boiler can be a considerable expense on it’s own, even if you pay via monthly finance.

Having your radiators replaced at the same time may seem like adding more expense, but by having new radiators at the same time as your boiler you will save money, as the system will need to be drained down anyway, making it easier for an engineer to fit them.

Additionally, many heating engineers will give you a discounted price for changing your boiler and radiators at the same time. Combining the efficiency of a new boiler and new radiators at the same time will also save you money on your heating bills.

Unlike having a boiler fitted; which has to be done by Gas Safe Registered engineers, changing radiators can be done by DIY enthusiasts. If you stick to the same width radiators and the pipework isn’t changing position then it’s not too difficult for a competent DIY enthusiast to do the job.


Installing a new, more powerful boiler can lead to leaks in older radiators, due to the pressure increase as water is pumped around the system at a more powerful rate. Leaks can be fixed relatively simply if you have a little DIY knowledge but it can be an unwelcome side-effect of a new boiler if you have older radiators.


If you’re thinking about a complete overhaul to your central heating system and wondering whether you need to replace the central heating pipework as well as the boiler and radiators, there are a few factors to consider.

Boiler kettling

If your boiler is ‘kettling’, also known as ‘dry boiler kettling’, the term for noise created by a boiler not working as it should do, then some further investigation is required. It’s called kettling as it sounds like a kettle boiling, makes sense so far.

So what causes kettling? I’m glad you asked. There are a few issues that can lead to kettling.

A leak in your system, either from the boiler or from your pipework can lead to kettling. Check your system for any noticeable leaks, starting from the boiler and the pipework leading from it. Next, check the pipework around your radiators – a leaking radiator could also lead to your boiler kettling.

If you aren’t able to detect any leaks with a manual search, then it may be time to call in the experts, unless you fancy pulling up some floorboards.

Another common cause of kettling is a build-up of ‘sludge’, as described earlier in this article.

If your boiler is suffering from kettling, then you may want to get your pipework checked out prior to installing a new boiler to make sure it’s not causing any of the issues listed above.

Uneven heat distribution

If your pipework is very hot coming out of the boiler, but the radiator temperature isn’t as hot, then it may be worth considering replacing your pipework as it may be suffering from corrosion or a pinhole leak somewhere.

hand on radiator checking heat output.

Stainless steel pipes

Although quite uncommon, some older houses may still have stainless steel pipes rather than the copper pipes which are now used. Stainless steel is a lot more prone to corrosion, which, as we learned above – can lead to kettling and sludge build-up (both bad).


The final factor worth considering when deciding whether or not to replace central heating pipework is your budget. Replacing the pipework in your system is not a cheap job, costing upwards of £1,500 and potentially much higher if you have a large home with a lot of radiators.

Often there is no need to replace pipework when upgrading your boiler or radiators, it’s costly, messy and often it serves no real purpose.

If you want the peace of mind in knowing that everything is new and won’t need replacing for a long time then it may be worth considering, or if the property in question is very old and the pipework hasn’t been updated in a long time.

It’s a rarity for pipework to need replacing, if you’re unsure, then get a Gas Safe Registered engineer to have a look at your pipework, they will carry out some tests and let you know if your pipework does need replacing.


If you are considering installing a new energy efficient boiler, you won’t maximise savings on your heating bill if it has to pump water through old, inefficient radiators and pipes.

Whilst boilers are replaced every 10-15 years on average, radiators often get overlooked as they can’t ‘break down’ as such, but they can underperform. Radiators that haven’t been updated in the last 10-15 years will have a high likelihood of internal corrosion and sludge deposits, hampering efficiency and putting a strain on your heating system.

If you haven’t had a look at new radiators for a while, you’d be surprised how appealing the designs can be and just how many different styles are available. Gone are the days of white block radiators, you can now choose a radiator that will actively complement the style of your room.

Obviously, cost is a consideration in deciding whether to replace your radiators at the same time as your new boiler; there are other cheaper options you may wish to consider to remedy any issues with performance your radiators have, before committing to a larger spend.

We would recommend only replacing central heating pipework if it is causing an issue with your boiler, or if any pipes are leaking, as it isn’t worth the disruption and the cost otherwise.

Replacing your radiators when installing a new boiler is recommended if you can afford it, as there are a range of benefits to installing new radiators.

Always ask an expert if you aren’t sure of anything and need some additional advice.

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