Your boiler is one of the most expensive and essential pieces of equipment you can have in a household – after all, it keeps us warm, powers the central heating and provides hot water for baths, showers or washing dishes. So when your boiler fails or needs replacing it can be a daunting time, and it’s a task that will always require help from a professional plumber or heating engineer. Here we will discuss the steps needed to remove, choose and install a new boiler, as well as the reasons why it’s so important to have your boiler regularly serviced and replaced when necessary.

Why is boiler maintenance so important?

It may feel like an unnecessary expense, but it’s so important to have your boiler serviced annually if you want it to last as long as possible. Servicing every year not only keeps the boiler’s warranty intact, but ensures it is safe and efficient as well. Faulty boilers can emit carbon monoxide, and exposure to the gas can be deadly even in small amounts. It’s thankfully rare, and boilers do have their own existing safety measures in place, but it’s still good practice to get a check done every year.

Regular servicing has perks too, and could reduce your fuel costs by up to 10% annually. It also helps spot any faults or issues early on, which could save you money in costly repairs further down the line.

How do you know when it’s time to replace your existing boiler?

A typical gas boiler should last between 10 and 15 years, and more towards the latter end if you get it serviced regularly. It’s a good idea to start saving for a new boiler if it’s approaching 15 years of use, but the plumber or heating engineer who does your next boiler service will be able to give you an idea of what condition it’s in. They can also advise you on boiler replacement costs, which may not be as much as you think.

If your boiler keeps failing then it’s more than likely to need a replacement, and you’ll save money on regular repairs in the long run. Other signs to look out for are escalating heating bills (an inefficient boiler uses more energy to heat up), strange hissing or popping noises, if your radiators are heating up slightly, but not as much as they should, or if there are any strange smells coming from the unit. The latter is particularly vital to have checked as it could be a sign of carbon monoxide gas, as mentioned above.

Removing the old unit

So now you’ve decided to replace your boiler, the first thing you’ll need to do is have the old unit removed. Again, for safety and convenience you should always get a professional to do this. You’ll need a Gas Safe registered engineer to shut the gas off at the meter and then break the gas feed before capping it so the appliance is no longer a working unit. They should also deal with the water valves to isolate the boiler from the water supply and may remove the gas pipe if no longer needed; it all depends on the type of new boiler being installed and whether it will be placed in the same spot or a different area of your home.

Selecting the right size

Selecting the right boiler for your home will depend on how much space you have, extent of use and the type of fuel used. A gas boiler is usually the cheapest option if your home runs off mains gas, or if you don’t have a gas supply then consider a low carbon heater such as a heat pump or biomass. If that doesn’t sound practical then you might want to consider getting a gas connection installed, your local gas company will be able to advise on cost and it may even be partly or fully funded.

The next thing to consider is whether to choose a regular boiler or a combi boiler; regular boilers have a separate hot water cylinder whereas combi boilers are all in one, and therefore a lot smaller. Regular boilers tend to be faster and more efficient, so if you have a large house or family then this is likely to be the best choice. If you live in a flat or a one to two person household then a combi boiler should be sufficient, and it will take up less space.

The size of a boiler is measured in kW (kilowatts) and combi boilers come in three general sizes, 24-27kW, 28-34kW and 35-42kW. As a general rule, a small house with around 10 radiators and one bathroom can be comfortably heated by a 24kW boiler. Most installers will consider the number of radiators, bathrooms and people in your home, and of course the larger the house, the more powerful the boiler required.

You can also calculate the number of British Thermal Units (Btu) required from your boiler in order to heat your home. It’s suggested that your heater should produce around 50 Btu per square foot to effectively heat the area and there are plenty of Btu calculators available online to help you decide which size boiler you need.


Once you’ve chosen a boiler you’ll need a registered Gas Safe engineer to install the new unit, for time management and convenience this is usually done on the same day your old boiler is removed. The cost and time spent on the installation will vary depending on the type and size of boiler you’ve chosen, but most can be fitted within a day. The heating engineer will install the boiler in the spot requested, and connect the unit via pumps and pipes to radiators, water outlets and the cold water mains supply. If you’ve chosen a regular, rather than a combi, boiler, they may have to connect hot and cold water storage tanks too. Reputable plumbers such as Prestige Plumbers in Southampton should be able to install all types of boiler, at Prestige we provide water heater installation, central heating, heating pumps, thermostats and more.

Most regular boilers will be installed in a loft or attic space out of sight and the kitchen is usually the best place for a combi boiler as they are very compact and don’t take up too much space. The installation will also include connecting your boiler to electrical controls, so you can alter the central heating without having to go to the boiler room directly.


Congratulations, you should now be in possession of a shiny new boiler and ready to settle in and get cosy this winter. After the expense and time spent on installation, of course you want to make sure that everything is working as it should. It’s worth testing your central heating system sooner rather than later; before the cold snap hits and gas companies become very busy. Wait until your boiler is cool and turn the thermostat (separate or part of the boiler) down to 0. Turn off the hot water then turn up the thermostat and check the boiler flares into life. After 10 minutes feel the radiators (best to check them all if you can) and make sure there is a steady even heat top and bottom. If all is working correctly then that’s it! – turn the thermostat down or off and enjoy your new toasty warmth. For combi boilers the process is even easier, simply turn on the hot taps and make sure they warm up with a steady, even flow.

At Prestige Plumbers, we understand you want to be in safe hands when it comes to installing a new boiler. We have a team of specialist central heating engineers with over 40 years of experience working in Southampton and the surrounding areas. We can provide water heater installation, immersion heaters, central heating repairs and much more. If you need a boiler service, brand new unit or any other plumbing or heating issues sorted, don’t hesitate to visit our website or get in touch today.