A boiler installation is one of the bigger decisions homeowners face. It’s not an emergency repair; it’s a planned project that changes your heating for the next 15-20 years. Getting boiler installation right means understanding what happens, how much time it takes, and what the bill will look like.
For most homes in London, a gas boiler installation takes one to three days. The cost ranges from GBP 2,500 to GBP 4,500 depending on the boiler type, your existing pipework, and whether you need new flue work. What matters most is whether you go with a local plumber or a big chain, whether the job needs extra work, and whether your installer takes time to explain what’s happening.
What happens during a boiler installation
The installer arrives with the new boiler, removal equipment, and tools. The first thing they do is turn off your current heating and water supply. Then they drain the system. This is straightforward if everything is accessible; it takes longer if pipes run through walls or under floors.
Next, they disconnect the old boiler from the flue, gas line, and pipes. They remove it. Depending on size and access, removal can be quick or take an hour. Then they fit the new boiler into the same space (usually), connect the gas line, connect the pipes, and fit a new flue if needed.
The flue is the pipe that takes exhaust gases outside. If you’re replacing a boiler in the same location with the same type of flue, this is fast. If the flue route needs to change (rare but it happens), the work takes longer and costs more.
Once everything is connected, the installer fills the system, bleeds air from the pipes, and commissions the boiler. Commissioning means testing it, checking for leaks, adjusting settings, and making sure the controls work. This is where a good installer spends time. A rushed commissioning causes problems later.
How long does a boiler installation take
In most cases, how long it takes to install a new boiler is between 1 and 3 days. A straightforward swap of a combi boiler in its original location usually takes 1 day. That’s roughly 6-8 hours of work. You lose heating and hot water during that time, so installations usually start early morning and finish by evening.
A system boiler installation (with a separate hot water tank) takes longer because of extra pipework. This might be 1.5 to 2 days. If your pipes are corroded or the flue needs rerouting, add another day. Any job that involves working in the loft or crawl spaces takes longer because of access and safety checks.
Delays happen. An old pipework connection that won’t budge. A rusted gas valve. A builder snagging the flue route before you knew the boiler was being installed. These aren’t routine, but they’re also not rare. A realistic timeline includes a 1 or 2 day buffer.
Boiler installation cost: what you’re paying for
The boiler itself is one cost. Labour is another. A new combi boiler costs GBP 1,500 to GBP 2,500 depending on the brand. Installation labour is usually GBP 800 to GBP 1,500. So a straightforward job totals GBP 2,300 to GBP 4,000.
Add extra if you need new pipework, a new flue, a power flushing service (to clean your heating pipes), or radiator work. Power flushing costs GBP 300 to GBP 600 and is worth doing if your system is more than 10 years old. New radiators are GBP 200-400 each plus labour.
Heating companies quote higher. British Gas and similar national brands quote GBP 3,500 to GBP 5,000 for the same job. They offer warranties and financing, which costs money. Local independent installers usually quote lower but your warranty is only as good as they are.
Gas Safe registration and your boiler installation certificate
Your boiler installer must be on the Gas Safe register. This is not optional. It’s a legal requirement in the UK. Gas Safe engineers have passed qualifications and are inspected. If someone offers to install your boiler and they’re not registered, walk away. You need the Gas Safe certificate to prove the work was done properly. You’ll need this for insurance, selling your home, and if anything goes wrong later.
The certificate comes after the boiler is commissioned. A good installer gives it to you on the day. It covers the installation only, not the boiler itself. Some boilers come with a manufacturer’s warranty (usually 5-10 years) but that’s separate from the installation certificate.
Do you need a new boiler
Boiler installation usually happens when your old one breaks and can’t be repaired, or when it’s old enough that a repair doesn’t make sense. A boiler older than 15 years often costs more to repair than a new installation would cost. Older boilers are also less efficient. A 20-year-old boiler might be 78% efficient. A new one is 90%+. Over time the savings add up.
If your boiler is still working but you’re concerned about reliability, get it serviced. A GBP 100-150 annual service catches problems early. If it breaks, you’ll have to replace it. If it’s old and you know it’s coming, planning a boiler installation in summer means you’re not paying for an emergency winter call-out.
Professional Boiler Installation in South London
Whether you’re planning a new boiler installation, replacing an older heating system, or simply trying to understand how long boiler installation takes and what it costs, getting advice from an experienced professional can make the process much easier.
For homeowners across South London, Plumr provides professional boiler installation, servicing, and heating solutions tailored to your home. Their experienced engineers can help you understand your boiler options, installation requirements, and the work involved, ensuring your new heating system is installed safely, efficiently, and correctly from the start.
FAQs
1. Can I get my boiler installed in one day?
Yes, most standard boiler installations finish in one day (6-8 hours). A combi boiler replacement in the same location is usually straightforward. System boilers and jobs with extra work like new pipework or flue changes take longer.
2. How much does a new boiler installation cost in the UK?
Expect GBP 2,500 to GBP 4,500 for a complete installation. This includes the boiler, labour, and standard pipework connections. Extra work like power flushing, new radiators, or flue changes adds GBP 300-1,000+. National chains charge more than local installers.
3. Do I need a Gas Safe certificate for my boiler installation?
Yes. By law in the UK, gas boiler installation must be done by a Gas Safe registered engineer. You get a certificate after installation. You’ll need this for your insurance, when selling your home, and to prove the work was done to code.
4.What happens to my old boiler during installation?
The installer disconnects it, drains it safely, and removes it. They dispose of it or recycle it. Some installers charge a disposal fee (usually GBP 50-100). Ask about this before they start work.
