When you are getting a new boiler perhaps from your boiler cover provider or when you talk to the heating engineer about your hot water needs from a new boiler, we think a good installer will mention some or all of the following for you to consider. If they don’t come up in conversation, ask about them.  A good installer will be able to give you a full understanding of the benefits of each extra and advise whether they are needed.

Boiler cover quote

Gas pipe

The gas pipe runs from the meter to the boiler and should be checked to ensure it is large enough in diameter to deliver sufficient gas to your new boiler. If a new gas pipe is required, it should be clean and free of any debris so as to ensure nothing untoward enters the boiler.

Condensate pipe

If the condensate pipe (which carries wastewater) is proposed to end into a rainwater downpipe, it must have an external air brake installed.

If installation options only allow for external routing, the installer must ensure that the pipework is protected from freezing temperatures, consistent with the instructions from the manufacturer.

Water treatment (cleansing and flushing)

Most heating systems will require at least an easy gravity cleanse and flush, with the addition of a chemical inhibitor on the final fill of the system. Very sludged systems may need a powerful flush.

A good installation should advise you of which is most suitable and their reasoning.

Some commons signs of a sludged system include cold spots on radiators, system noise, and excessive heat-up times.  You can often get a sense of how clean or dirty the system by carefully bleeding a little water from a radiator valve, using a tissue.

When refilling the heating system, ensure the installer adds a chemical inhibitor to protect against the build-up of dirt and corrosion.

System filters/scale reducers

Scale reducers are especially good for combi boilers installed in a hard-water area. Ask your installer if you need them, as they can increase the longevity of a boiler.

It may be that a flush or system filter does not need to happen in all cases, but each of them should at least be considered by you and the installer before boiler installation.

Fitting a new boiler into a dirty or unsuitable system is a sure-fire step into reliability problems.

Plume effect (water vapour from the boiler flue)

How big a plume are you likely to get from the condensate and where is it going to be situated?

Will the neighbours complain because of its placement?

It is possible to take the plume away using an additional pipe called a plume management kit.

Heating controls

Is your thermostat reliable? A smart thermostat from Nest can be integrated into your boiler saving you hundreds each year.


Some older radiators may be inefficient or have internal corrosion – which means they may need replacing, especially true if you’re renovating a place too.

Additional energy-saving measures 

New government legislation requires that each new boiler installation includes at least one of four energy-saving measures. You can choose from flue gas heat recovery, load-compensating thermostats, weather-compensating thermostats or smart heating controls.  Your installer should be able to talk you through the advantages and disadvantages of each and advise on the most appropriate for your home.

Taking these actions will help to ensure reliable operation of your new boiler.

A combi to combi swap from a good engineer will take approximately 4-6 hours. Things get more complicated if you’re moving from a standard/system boiler to a combi. This could usually take anywhere from 1-2 days.

A system boiler will have a separate water tank which will need to be removed if you are switching to a combi boiler. In a similar fashion, a standard boiler has a separate hot water storage tank and a water feed tank usually located in the attic.

The water storage tank will need to be fully drained and potentially removed from the property. Engineers will also need to re-pipe the central heating system to accommodate your new boiler, this typically is a minor job – if this was to be a lot of time this would be discussed as part of your quote.

Let’s talk about the price of installations then. It doesn’t have to make your eyes water if you have some form of home and contents insurance (i.e. where your boiler is faulty, not just because you felt like having a new boiler installed).

Installation of a new combi boiler

Approximate cost with mid-range boiler

Time taken

1) Replacing an existing combi boiler with a new boiler, in the same part of the home£2,0004-6 hours
2) Replacing an existing combi boiler with a new boiler, in a new part of the home£2,6001-2 days

After showing you how to use your new boiler, your boiler engineer should clean up!

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