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Megaflo Boilers Explained, Reviewed, Pros & Cons

megaflo boilers

Megaflo boilers have been causing some confusion for visitors interested in finding out more about the range of boilers they can choose from, and also in terms of the common misspelling of “Megaflow”!

To allay this confusion, our team decided to write this article to give you the latest and accurate background knowledge you need.

The name ‘Megaflo’ doesn’t actually refer to a specific manufacturer or model of boiler.

In fact, it is a more casual term for an ‘unvented hot water cylinder’ which is used in a high-pressure boiler.

The name was first coined when boiler manufacturer Heatra Sadia first produced this style of boiler and called it the ‘Megaflo’.

Since then, the name has stuck around and the industry now applies it to this kind of boiler no matter who the manufacturer.

In this article, we take a detailed look at Megaflo boilers to give you insight into how they function and the type of features you can expect.

Read on to find out more about:

  • what a Megaflo boiler is,
  • how Megaflo boilers work,
  • who would benefit from installing a Megaflo boiler,
  • how much it costs to install a Megaflo boiler,
  • the pros and cons of Megaflo boilers,
  • who currently manufacture Megaflo boilers,
  • warranties available on Megaflo boilers, and
  • megaflo top tips and extra safety information
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What is a Megaflo boiler?

As we mentioned above, the Megaflo name came about when Heatrae Sadia invented a new unvented hot water cylinder which is used in many of their electrically-powered central heating systems. 

The Megaflo system is composed of stainless steel and the cylinder in it may be either indirect or direct – this refers to the method of heating the water.

If the cylinder is indirect, it is heated by a separate regular boiler or system boiler whereas a direct Megaflo boiler has a built-in element to create the hot water for your home.

There may also be a switch installed alongside your cylinder should your boiler fail for any reason which activates the immersion coil within the cylinder so that you continue to be supplied with hot water.

However, manufacturers do not recommend that you have the boiler and immersion switch on at the same time because this can cause serious issues to your heating system.

How does a Megaflo boiler work?

The main point of appeal for a Megaflo boiler is that they are connected directly to the cold water mains supply.

This means that, despite the fact that there is no need for a water storage tank in your loft, your home still benefits from rapidly-produced piping hot water quickly with a high water pressure.

This is beneficial because it means your household enjoys a greater amount of hot water at one time. No more waiting for someone to get out the shower before you can do the washing-up!

Megaflo boilers heat up the cold water either directly or indirectly (as previously mentioned) at a quick speed and then they store it in their unvented cylinder. 

Megaflo boilers can do this because of their in-built expansion vessel.

This allows space for the water to expand as it heats up making sure the water is being heated safely

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Who would benefit from installing a Megaflo boiler?

If one or more of the following situations apply to you and your family, you could consider investing in a Megaflo boiler:

  • You have a demand for high water pressure
  • You have enough storage space for a cylinder
  • You find that you often tend to need to run multiple hot taps at any one time
  • Your property allows for a 16 litre per minute water flow rate from the mains
  • You have 1 to 1.5 bars of mains water pressure
  • You have moderately new radiators that can handle the pressure of a Megaflo boiler (ask your engineer about this if you’re unsure).

How much does it cost to install a Megaflo boiler?

As with any boiler replacement or installation project, costs can vary considerably depending on:

  • who you choose to carry out the work and 
  • how much preparation your property requires for the upgrade. 

There really is no fixed price for installing a Megaflo boiler and it could range from £500 to £2,000.

It’s always advisable to obtain a few quotes from local firms in order to get the best price for the job.

The price for the cylinder itself will also vary depending on what model you opt for.

However, to give you some perspective, a 210L Megaflo boiler can cost around £600 before factoring in installation and optional extras.

The main difference in cost between choosing a Megaflo boiler and a combi boiler system is that combi boilers don’t need a cylinder therefore making the project slightly cheaper.

Pros of Megaflo boilers

Here, we have listed the benefits of installing a Megaflo boiler system in your household:

  • They don’t require as much space as a traditional boiler which needs loft room for the storage tank. This means that you can install one in a smaller property and not worry about impacting your remaining storage space.
  • There is less building work involved than installing a regular boiler because you don’t need to go up into the loft and plumb in extra pipework, therefore resulting in less stress, mess and installation-induced headaches.
  • You have the choice of locations as to where you want your Megaflo boiler installed and can be moved much like the flue of a combi boiler, if required.
  • Megaflo boilers tend to be easy to install and their spare parts are readily available should you need a replacement component a few years down the line.
  • If a fault does develop with the boiler or components, the system is compatible with solar PV, a renewable energy source, which can provide you with back-up power.
  • You will always get high water pressure even if more than one person is using the bath, shower, or hot tap at any one time.
  • They have built in safety features such as automatic cylinder thermostat shut down to avoid overheating and to keep water at optimum temperature.
  • If the water does get too hot, the pressure relief valve kicks into action to remove the water and reduce pressure without you having to do anything.

Cons of Megaflo boilers

As with all central heating systems, there are some drawbacks you need to consider to work out if this set up is going to be suitable for your property:

  • If you live in an area of low water pressure, the Megaflo won’t be able to compensate against this so you will not benefit from the high water pressure they can produce.
  • You need to ensure a flow rate rest is completed by an engineer to tell you the level of your mains supply before installing a Megaflo.
  • They can be noisy whilst operating which may be an issue if you are partial to peace and quiet in your home.
  • You will need to check your properties pipework before installation to make sure it can withstand the pressure of the new system.
  • If your pipes aren’t strong enough, you will have to pay to upgrade your system which can be costly, take considerable time, and be inconvenient for those living in the house. 
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What Megaflo boilers are currently available?

There are currently four manufacturers making Megaflo boiler systems in the UK.

Heatrae Sadia

Heatrae Sadia is the company most commonly associated with the Megaflo style of boiler.

They are the UK’s biggest producer of the Megaflo boiler alongside electric water heaters and sell their products all over the world.

They were founded in Norwich almost a century ago so they have a vast amount of knowledge and experience in this sector.

Heatrae Sadia bought the Megaflo brand name in 1993, manufactures Megaflo cylinders, and also has a budget range named PremierPlus for those working within tighter financial restraints. 

Worcester Bosch

Worcester Bosch are a household name when it comes to central heating options so it comes as no surprise that they too offer a Megaflo style of boiler. 

They are a very reputable company and even hold The Royal Warrant seal of approval as their products heat some of Her Majesty The Queen’s estates. 

Within the Worcester Bosch range, the Greenstore unvented cylinders have been designed to work alongside the Greenstar boilers and Greenskies solar panels.

They come in a range of sizes from 90 litres to 300 litres so you can choose a model suitable for your needs. 


Telford, a 2002-established family run business, offers a lifetime guarantee on some of their Megaflo boiler models such as the Telford Tempest. 

Telford produces both domestic and commercial Megaflo boilers ranging in capacity from 500 litres to 4,000 litres.

They also boast that their stainless steel cylinders are up to 40% thicker than its competitors. 


The fourth company in the UK marketplace is Gledhill, founded by the Blackhill-based Gledhill brothers in 1926.

They have grown to include numerous manufacturing depots all over the UK.

The company pioneered StainlessLite cylinders offering an exceptionally light carrying weight which makes for a smooth installation process. 

That particular model is a horizontally fitted system which is beneficial for installation locations with a low headroom, such as attics or storage rooms. 

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What is the warranty on Megaflo boilers?

As with all boiler systems, getting a generous warranty is essential for your peace of mind.

It’s important to double check the guidelines you need to follow beforehand to avoid invalidating your warranty

One of the main issues with the life of boilers in the UK is the level of water hardness in your area.

Soft and hard water can create different issues such as limescale which can cause faults if not serviced regularly. 

Different companies offer varying levels of warranty ranging from 10 to 25-years depending on the specific model of boiler.

Many companies also offer the chance to extend your warranty at an additional cost.

They will only do this if you use a certified Gas Safe engineer to install the product so it’s always worth asking about this when obtaining your quote. 

Heatrae Sadia offer a generous 25-year warranty on all of their Megaflo boiler models.

In the wider boiler marketing, this is an exceptional deal and possibly why they are so popular with the UK public. 

However, it’s also important to note that different internal components in your Megaflo boiler system may have varying warranty lengths so always read the small print when purchasing your boiler. 

Megaflo top tips and safety information

Boilers can be dangerous pieces of equipment if not serviced regularly and looked after well. 

Here, we have listed some top tips for getting the most out of your Megaflo boiler as well as some safety information for you to be aware of.

  • The temperature of the water inside the cylinder should be between 60c and 65c

This is controlled by an internal thermostat as exceeding 100 c would be extremely dangerous as the boiler could explode.

  • If the boiler is unable to reach the 60c – 65c level, you risk harmful bacteria growing inside the cylinder.

This bacteria would come through the hot tap and it could potentially cause you and your family to become ill.

  • Any Megaflo boiler must be installed by a Gas Safe engineer to make sure all fixtures and fittings are securely in place.

So you run no risk of serious issues, the installer must have an Unvented Hot Water Qualification to legally install or service these styles of boilers.

  • The extra safety precaution of automatic shut off has been programmed into Megaflo boilers so, should the water reach 85c, it automatically turns off to prevent any further damage.
  • It’s important to be aware that water expands as it heats.

This expansion results in an increase in water pressure and therefore creates the need for extra space in the storage cylinder.

  • If the water gets too hot without enough room to expand the boiler can explode.

To avoid this issue, all Megaflo boilers have automatic temperature controls and release valves to safety dispose of excess hot water down the drain.

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Save up to 54% on the installation of your new Megaflo boiler

If you think your property would benefit from a Megaflo boiler, fill in our online form to save up to 54% of the cost of the supply and the installation.  

We get in touch with three or four local, trusted and Gas Safe regulated engineers with your query who will contact you directly with a free quote and any relevant advice. 

The best part is that our service is completely free and it is no obligation even if you decide not to proceed so you have nothing to lose. 

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Andy is one of the HomeSage founders and an occasional content contributor. His love for boilers is only just outweighed by his love for football.