How Quickly Can A New Boiler Be Installed?

gas safe
boiler-Installation London
boiler installer London

This content was supervised by an expert engineer from MML PLumbing Ltd.

Let’s see how long it takes to install a new boiler

Hard to say the exact time. Boiler swaps are not the smallest jobs. Not as easy as it looks, but it is a huge responsibility to the installers. The installation depends on both the type of old boiler and the current heating system design. Of course, we can always estimate the installation duration online. We installed a lot of the heating systems ourselves in the past and our estimation accuracy online is 90%. The installation time depends on many factors. In this topic, we dive in and write a proper description of what can you expect after you call one of our gas boiler installers for the installation. As you will see, every central heating system has its difficulty.

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Boiler installations can be as simple as:

  • a combination boiler change.
  • more time-consuming like the system to combi installation.
  • it can be a conventional system conversion to a combi.

Please note, that there is a big difference between boiler replacement and conversion. Also, you have to keep in mind if we have to replace the same boiler or type of boiler with a different location that takes an extra 0.5 to 1 day. So let’s dive in. We guide you through to understand what we have to deal with and how fast can we do the boiler replacement and installation.

How long does it take to install or replace a combi boiler?

Combi boiler diagram

Combination boilers are easy to install. This is the fastest and simplest boiler installation or energy-efficient combi boiler swap. Do you already have a combination boiler? Do you want to update it because it breaks down every time? If our gas-safe registered engineer only has to replace the boiler this would take about 4-6 hours. But we speak about a simple straight boiler swap, with no complication. This means that our engineer doesn’t have to change a lot of components! Also, you have good water flow at the taps (you should have this if you have a combination boiler already). Also, it is a big advantage if the previous installer runs the gas supply pipes from mains in 22mm and not 15 mm. In some situations, we have to increase the pipe size to 22 mm which would be an extra 0.5 days. But in most cases, we don’t need to change anything.

Just to mention, if the existing system of your central heating is clean and it needs only a small chemical cleaning then the whole installation will be ready the same as for like swap day. However, if your heating system is dirty you might need a system wash.

So to recap, it is possible to replace the broken boiler, in 4-6 hours. But without any power flushing or extra radiator installation. Also, we have to fit a boiler for the replacement boiler in the same location.

To keep the boiler warranty, it is recommended by the boiler manufacturer to fit a separate water tank and a magnetic system filter before you fit a boiler. Also, sometimes it is enough to carry out half a day of system chemical wash. The chemical wash improves your heating system warranty and performance.

For a more accurate estimate go to our Quote My Job site and fill in our 2-minute form. 

Combi boilers are quite popular in every UK home. If you want to install a top-quality high-efficiency boiler, contact us today!

How long does it take to convert a regular or system boiler to a combi boiler system?

To convert an old system boiler together with the central heating system to a modern one where we use a high-efficiency combi boiler will take 2 days. This is the most time-consuming job of all boiler installations. However, there are a few situations you have to count which can add up to a few hours to the installation process.

Upgrading-from-a-heat-only-boiler

Why the boiler upgrade is time-consuming?

In this section, we guide you through why a conventional boiler upgrade is the longest of all. To read more about how the boilers are working in your home check out our boiler types in our installation guide.

You probably have a hot water cylinder!

As you might know, you also have a hot water cylinder in the airing cupboard which supplies hot water to your bathrooms. When we convert this central heating system to a combination boiler we have to take out the hot water cylinder. This would take 3 hours for our heating engineer. We need to change the existing pipework, so they will be suitable for the hot water and gas supply that comes from the combination boiler. We also have to cut out the motorised valves, the old pump and other components. In most of the places, the current heating system and hot water pipes are looking like spaghetti junctions so our engineer will have to check and mark up everything.

Do you have cold water and an F&E tank in the loft?

If yes, we have to take out this cold water tank which supplies water to your bathrooms.

The F&E tank provides safety for central heating. It works similarly to an expansion vessel in a sealed system. Simply when your heating system heats up, the water will expand. This excess water will go up to the F&E tank helping your system to work properly. The F&E tank also tops up your central heating with cold water. Again we have to take out both tanks from the loft. As you can see this is a time-consuming job.

How is your pipework condition?

We need to investigate your pipework condition. In your old heating system, the pressure was probably 0.75 bar which increases to 1.2 bar after we install a new combi boiler. But when the central heating heats up, this pressure can go above 1.5 bar.

We have to make sure your pipework is in good condition. Anyway, you end up with lots of leaks under the floorboard. What we normally do is to take out all the components, change the pipework and also do a test between 1-3 bar. If the test is successful, we know that your new pipework only can hold 1.2 bar.

We have to access the pipework and lift some floorboards!

Our engineers take care of your home, putting protection on the floor and the area where they work. But in some scenarios, we have to cut up some floorboards to access gas pipes, supply pipes or change the pipework. As you see, this can also take a few hours from our installation process.

How long does it take for us to move your boiler?

If you want to relocate the boiler flue to a different location this can take an extra 1.5 days. Let me explain, why! Boiler installation The pipework needs to run safely and properly secured. To run the correct size of the gas supply pipe, our professional gas engineer calculates the correct pipe diameter. In a few cases, the pipe needs to be changed to 22 mm. We also have to drill a new flue hole for the gas boiler and flue. This will take about 1 hour.

Do we have to replace the gas mains?

Now we can talk about this topic and what everyone wants to know. Changing the gas safety supply pipe from the old gas mains to a bigger one would take an extra 0.5 days. Gas-safe regulations say that the whole gas-safe side pipe has to be at least 22mm in size.

But what about if the gas meter is close to the boiler?

In this case, we have to check the gas pressure so we can decide if your old pipe will be suitable for take to replace your new combi boiler.

Let’s give you an example:

If your gas meter is nearby to the boiler, and your cooker is at a close distance, then this might work. We have to measure the gas pressure at the meter, if this is 23 millibars then we need 22 millibars at the boiler test point. Even if we run the cooker and the electric boiler both at maximum performance. If the measurements are correct, we can use the old pipe. One of our qualified engineers can carry out all the tests and explain to you what are the outcomes.

Why does a boiler upgrade take so long?

Read on and discover how we can help you with our exceptional services.

How quickly can we convert an old conventional system to a combi boiler system?

This particular change will take only 2 days. Please note, that everything depends on the circumstances of the old central heating. Even in this scenario, we can finish the current boiler system upgrade and installation and install a new boiler system upgrade in less than 4.5 days with the benchmark filled.

If you thinking of converting your old heating system to a combi boiler ask for our advice and your options. One of our qualified certified engineers will help you out.

Do I need chemical flushing or a system clean when installing a new boiler?

It all depends on how your central heating performs now and if any system protection was used in the past.

How long does it take the system to clean?

It takes about 3-6 hours depending on how many radiators you have and how dirty is your central heating.

One of our heating engineers will check the system by taking a water sample. Also, we check your system with a thermal image camera.

You don’t need a system clean in every case. Sometimes it’s enough just a smaller chemical flush.

Not all boiler manufacturer says it is mandatory the power flushing. We can help you decide whether you need central heating cleaning or not.

Call our company number at 020 8355 0840 and we will guide you through the steps.

How fast can a new boiler be installed with a few new radiators?

After we finish the installation we check that everything is working safely:

  • We check if there is any leak.
  • We do a gas tightness test.
  • We carry out boiler combustion analysis.
  • We fill up the benchmark.
  • And finally, we explain to you how your new boiler and control work.

But our job is not finished here. We still have to do some paperwork in the office. We have to make sure all of the boilers that we install are registered to the manufacturer so you can have up to 10 years of part and labour coverage. Also, we have to register your boiler to the gas safe.

Do you need a new boiler?

Discover swift and reliable boiler installations tailored to your home’s unique requirements. While installation times may vary, our skilled gas-safe registered engineer can typically complete a new combi boiler installation within a single day on average. Even if unexpected complications arise during the upgrade from an old combi boiler, rest assured that we strive to finish the new combi boiler swap installation within a maximum of 2 days together with a power flush.

Take the first step towards a hassle-free boiler estimate by calculating your installation price online. In just 30 seconds you will receive a fixed installation price.

Contact us today to discuss your installation requirements. We are committed to working within your budget and guaranteeing a reasonable price for our exceptional services.

How much does a new boiler installation cost?

To answer this question properly we need a little information about the back boiler part. If you want to have a new back boiler installed, go and fill up a 2-minute Quote Your Work form with the installation details and we can give you an accurate estimate.

Here is a rough installation estimate:

  • A low-end boiler with installation, boiler (included) and system cleaning can cost you between £1500-£1950
  • Mid-range boiler with installation, boiler (included) and system cleaning can cost you between £1800- £2400
  • Premium boiler with installation, boiler (included) and system cleaning can start from £2400.


*Remember this is just a rough estimate. Prices can be lower or higher. The boiler fitted in the same location

To give you a more accurate estimate give us a call at 020 8355 0840. Answer a few technical questions and we will tell you how much the new boiler installation will be. If you like the price, we will visit you run some tests and give you a fixed price on your new installation.

Do you want to get the best prices on a new boiler?

If yes, you are one step closer to your new boiler. You call us at 020 8355 0840, we give you an estimate. We have the most affordable rates on the market. Do you think that our first estimate is too high for your budget? We can give you a second estimate and walk you through what this means.

In the installation package we can change the:

  • boiler brand and type.
  • parts that we use.
  • we can use different types of controls.
  • We will match your budget and you can have a new boiler at a reasonable price.

Frequently Asked Questions

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