We are seeing more and more people installing Megaflo heating systems in their homes, but what are they and why are they becoming so popular? Well, a Megaflo is essentially a brand of hot water tank – but the major difference is how they are plumbed in.
Older, traditional heat only systems have cold water expansion tanks up in the roof, and it is the height of this cold water tank above the hot water cylinder that generates the pressure that delivers the hot water to the taps. For taps on the lower floors, this tends to work perfectly, but for bathrooms upstairs the pressure is often not great and so you get issues like weak showers or baths that take an age to fill up. In many cases, this is sorted by installing a pump that drives the water from the hot water tank to the required faucet, but installing a Megaflo does away with all these issues!
Megaflo – an unvented hot water cylinder
Megaflo cylinders form what is known as an unvented system – this is pressurised to mains water pressure, ensuring a strong flow of hot water when you turn a tap on in the home, regardless of where it is located. The actual pressure in this type of hot water cylinder is normally about 3 bar, which is equivalent to a cold water tank being 30m above the tap for a heat-only system. The cold water is fed into the bottom of the tank at mains pressure. This forces the hot water out at the top and this then travels to the tap. This means that you have great pressure all the time, so gone are the days of the dreaded dripping shower!
Since the volume of water increases as it gets heated, all unvented systems require some sort of expansion vessel to absorb this increased volume. The nice thing about the Megaflo models is that they contain an enclosed air bubble within the tank itself, which acts as the expansion vessel so you don’t require an external one. It’s worth mentioning, though, that over time the air bubble can be absorbed into the water; this can be recharged as part of an annual boiler service.
Like other heating systems, the hot water within the Megaflo can be produced by immersion units (so heated with electricity), boilers or even solar thermal. If you buy a twin-coil unit, you can feed the tank with two sources of hot water: a boiler plus solar thermal, for example.
Although there are lots of hot water tanks suitable for use within unvented systems, the Megaflo is the market leader in the UK. This is partly because the brand, but the performance of these cylinders really is very good. They are tested to withstand 15 bar of pressure, so you can be sure they are up to the job of operating at these higher pressures (compared to conventional heat-only systems).
Megaflo cylinders have lots of safety features
Megaflo cylinders also have great safety features incorporated into them. This includes thermostatic controls that prevent the water in the cylinder ever being heated above 100 degrees centigrade, as well as expansion release valves that allow expansion to take place if the cylinder doesn’t perform correctly. There is also a temperature and pressure release valve situated on top of the tank, which vents water if it hits unsafe temperature levels. Megaflo cylinders also include a 60mm-thick layer of polyurethane foam to insulate them. This ensures that once the hot water is created it stays warm for longer, minimising the need to reheat the water.
So having looked at the advantages of the Megaflo cylinders, what are the issues with them? Well, not many performance-wise, however they are significantly more expensive than other unvented cylinders.
Unvented systems are also generally more expensive to install compared to heat-only boilers. They must be installed by a competent and qualified G3 engineer; this is a legal requirement in the UK and all installations must be certified and registered with the local council. This means that your average plumber/heating engineer will not actually be allowed to install one in your home.
The other issue – and this is not just Megaflo, but all unvented systems – is the high pressures involved. Obviously if everything is working correctly then the performance will be great, but all pipework needs to be able to withstand the higher pressures!
The performance of the Megaflo cylinders makes them extremely popular – the hot water is delivered to every tap at mains pressure and the tanks themselves are well insulated, ensuring they operate very efficiently – but be prepared to pay more to install one of these in your home!
Installing a new Megaflo
Are you interested in installing a Megaflo? We have scoured the country for the best installers, so that we can make sure we only recommend those we really trust.
Are megaflo systems compatible with air source heat pumps?
if you use a dual tank Megaflo system would solar energy using iboost heat first tank for hot water and second immersion could be wired to heat water for heating? reducing cost of using gas boiler for all heating? or is only possible for hot water only. Thanks
We have 2 showers one with a good flow the other is just a dribble why and how to fix
Hi Mike, we’re changing the boiler from oil to an air source heat pump, can we keep our 18month old Megaflow eco210i or do we need to dump it for a heat source specific tank that is apparently more efficient (has a longer coil)
My son’s house has a Megaflow and experiences a prolonged hammering noise which seems to stop when a cold tap is opened. Could this be related to the Megaflow installation / servicing?
I have had an electric Megalo Heatrae Sadia for 20 years and its never let me down and is still going strong, highly recommended! However, with the huge increase in energy costs recently, I would like to know whether its possible to put it on a timer so its not on 24/7 to reduce energy consumption before I call a plumber out and pay an unnecessary call out charge. Any advice greatly received
am concerned for my children being scolded from the hot water that has suddenly become very hot. How do I adjust temperature please.
Our hot water has suddenly heated up to near boiling coming out of the taps, how do you turn it down please. Thank you.
Have a 3 storey with megaflo 2 adults, how long do I need to have water turned on a day to heat. ? Have had it on for about 7 hours a day but have changed to an hour in the morning and an hour in the evening. Will this be sufficient? Thanks
We have inherited a megaflo system and put in a new green star boiler. The water pressure in the bath and basin upstairs is now really poor. Does this mean that I have to mention the air. bubble issue when we get the boiler serviced?
What is open therm ? I have MEGAFLOW cylinder , How do I know if it is open therm to suite Nest system.?
How do you turn a Megaflo High efficency HEATRAE SADIA ON? We have issues with our main boiler but we need hot water as Plumber not coming till tomorrow. Many Thanks
Why can’t you put a basic price list on your website to give people an idea of how likely it is they can afford it?
I have megaflo for last 8 years. Recently I had to call plumber twice due to poor flow in shower. He noted lime sc6blockage in hot water filter and has recommended checking lime scale in megaflo. Kindly advice
I have bits of silica type deposits in my tap and shower filter. Can a mag flow cause these bits and then get caught up in the filters ?
What is needed to connect a megaflo unvented heater to Pv panels. Do I need a special heater for this supply. Hot water only.
Hi, I can see that unvented cylinder have different flow rate. Once fitted, would this flow rate capped anyway to the main flow rate or are unvented cylinder able to increase flow rate compared to the main? Many thanks.
How often would it need to be re-energised?
“over time the air bubble can be absorbed into the water; this can be recharged as part of an annual boiler service” It is a waste of money to pay for an engineer just to do this – it is very simple to do – instructions are widely available.
How long between recharging?
How long should a Megaflo water tank last? I’ve had mine for 10 years and the plumber is recommending it is replaced to resolve a leak rather than fixing it.
We have a Vaillant combi- boiler which is only 4 years old. We currently have a bathroom and a separate toilet and we are considering getting a loft extension with an additional bathroom. We want to ensure we have sufficient water pressure and capacity in the loft extension. Is it possible to install a megaflow system whilst keeping the combi boiler that we have or do we need to get rid of the combi boiler and install a megaflow?
We have a Megaflo running solely off gas, in South West London. The times that the heating is on is 4 hours in the morning and 6 1/2 hours in the evening. Our gas bill is over 90 pounds a month which seems high. Is there a simple explanation?
Hi,
We recently had a mega flow unvented tank installed by a fitter who seems to be very busy since the installation.
Should the tank have a stop-cock on the hot water outflow from the tank? Ours doesn’t and we have to empty the tank each time we need to do this and that’s hot water wasted!
Thanks
Ash
Myy megaflow system is broken i need to know were can i get new parts thanks you
Hi Lora, We’d recommend you go right to the manufacturers, Heatrae Sadia.
Many thanks,
Harriet
I have a Megaflow system – I need to change a hot tap washer. If I turn off the mains cold water, will this stop the flow to the hot tap and depressurise the system through the hot tap – can I then change the washer and put the mains on again and will the system then pressurize itself as before
We live in an old cottage and a plumber has suggested we consider installing a Megaflow tank as we currently have to use pumps for the showers and baths. However, I’m concerned about having sufficient mains pressure, is there a way to test this before purchasing an expensive Megaflow tank?
Hi Deborah,
A plumber will be able to test the water pressure for you relatively easily.
Hi
Is it possible to adjust the temperature of the hot water from a Megaflo system or is it factory set?
Any info greatly appreciated.
I am interested in how the temperature is set as the water is too hot to wash in without adding cold water
Hi.
We have a Megaflo system installed in our house but we have a major problem with the cold water inlet feed condensating.
We have converted a small utility room to a dedicated space for our heating system. The problem is so bad that it looks like the wall with the majority of the pipe work fixed to it will soon have the plaster falling away. We have put a small dehumidifier in the room and have the door open as much as possible but do you have any suggestions as to why this is happening and how to rectify the issue?
Thanks, Adrian
I would like to find out your phone number so I can ask you questions.
Hi
It’s 07976906194
Thanks, Adrian
Hi
We have a Megaflo system and yes the pressure lowers when someone opens a tap anywhere else. The hot water also runs out after a shower in the morning. Have had the BG Engineer around again after a annual service but he could not find any issues. Do we need a more qualified expert?
Thank you.
hi, why do we run out of water after two showers and some washing up?
We have a mega flow high efficiency, heatrae Sadia.
Do we need a plumber or is this normal? If so, it’s quite frustrating.
Hi James i have a megaflo tank – do i need to leave it on 24/7 as I think this is more expensive = i have had a timer fitted but not sure how many hours a day I need to leave it on? Also I have two panels on the front of the megaflo (if the megaflo stops working i have to reset it by unscrewing one of these panels and pressing the reset button). Also one of the panels is not working = do i need both of the panels to work to get a proper water supply?
Hi
We have a Megaflo system. The shower runs hot but when we run the bath this is just warm. Can you help . We live in a five year old flat.
Sounds like a technical issue – speak to Megaflo!
We have recently had a megaflow system installed. We are happy with the hot water supplied. However we find that it only works at one exit point at a time. i.e. when shower is running in one room turning hot tap on in another completely shuts shower off. Why is this?
Hi Andy,
So a megaflow is a pressurised system. Water will be pushed out of the top of the tank at the rate at which water enters the bottom via the mains water connection. If the rate of water coming into your home is not particularly high then unfortunately you will get the situation you are experiencing. You can get the water company to increase the rate at which water enters the home though – it normally costs about £3k to get this done, but this should solve the issue.
How do you turn a MEGAFLOW HIGH EFFICENCY HEATRAE SADIA ON as we never had to turn it on as we always used our main boiler.
Many Thanks
Hi,
I am living in a two bed flat. I had a direct unvented water tank using economy 7. It stopped working so need to replace. I have seen people mention about Heatbank hot water system (heat source is external to the tank, good pressure and no annual check). Doea Heatbank work with electric source please? Can any plumber install or need specific certification? Could you please advice.
G3 Engineer means, what difference from normal plumber who does boiler work.
Hi, we are looking for a hot water cylinder that is powered by solar energy.
We will not have a boiler and have been told megaflo does them.
Is this correct and if so how much ?
We would need a 300l system and would require supply only as it would be fitted in France.
Thank you
Do Megaflow pressurised unvented hot water tanks need regular servicing?
Hi Bill, we always recommend getting your boiler checked on a yearly basis. Having a yearly gas safe certificate is a legal requirement when you rent your property and we do think this is good practise for any household to be honest, so that is the time to get the megaflo checked.
What does it cost for an annual check for an electric Megaflo System in West London?
Hi Kandiah, I am not sure exactly, but I would be suprised if it was over £100.
Would a megaflo unvented cylinder be appropriate to replace our current unvented cylinder which is run jointly from a 3 oven oil-fired Raeburn and electric sources?
I have recently had the hot and cold pipes rerouted and now cannot get hot water produced by the boiler but can using the immersion heater. The boiler has been checked and is fine. The heating system is working. Any thoughts please?
Why can’t I get hot water when gas off and immersion heater light on red
I am not sure Julie, best to get a gas safe engineer in to come and take a look! Sorry we can’t be more help!
I want to install a mega flow system in our 4 bedroom house but have a micro ore pipe system on thie heating side. Will they take the increased pressure or is this adjustable for the heating side? Thanks Geoff
Hi
We have a one bedroom flat, at the moment the heating and hot water is electric with pumped hot water system. We would like to install a Megaflow system with electric single emmersion heater . What size of Megaflow you recommend and what is approx. cost of the material and also the total cost with installation. The flat is located in Wimbledon .
We’ve just had a 250litre megaflow cylinder installed in our 2 bed 2 bath flat replacing a traditional gravity system with pump. We opted for the 2 elements so we could boost if required. This has proved to be the best investment we made. We can comfortably have a bath and shower and wash up by setting the time to heat for 2 hours overnight with a 1 hour boost midday and it’s perfect.
Hi, We have a conventional gravity fed water system and an old (faithful) Glow Worm Fuelsaver F boiler in our 4 bedroom 2 bath house. Now wish to change the boiler and install a Megoflow system. Incoming water pressure is 2.5. Can you suggest what type of boiler would be suitable for a Megoflow system?
Thanks
We are about to install a megaflow in our small new utility room .. in the same room we will have our clothes drying on an airer .. does the Megaflow itself give out any heat? … was hoping for dual purpose so the megaflow will help to get clothes dried? .. my husband thinks we need underfloor heating in the utility to help dry out the laundry .. would appreciate your guidance please. Thanks
Our Megaflo is installed in a small enclosure on the first floor and that enclosure is quite hot as against the rest of the house. IMHO the room housing the Megaflo should not need any additional heating.
Hi, You stated that the system will not heat above 1000c, should this be 100c ???
No this is a special boiler which can heat water to 1000 degrees.
We live in a flat within a house built in 1750. The plumbing is awful. Is there an unvented system which doesn’t need an outside overflow connection?
System boilers do have these are safety features on the whole.
I have recently moved to a new house with a Megaflo system(not sure how old it is), fantastic pressure to start with but soon reduces & seems to get colder as pressure decreases, leave for a few minutes & pressure & heat return.I’m confused. Any ideas?
Brendon
Hi Brendon – a megaflow (system boiler) should have fixed pressure – the water coming in from the mains at the bottom of the tank expels the warm water at the top of the tank. There really should be no pressure drop at all – so definitely worth getting a heating engineer round to discuss.
My son has recently had such a system fitted. He is under the impression that he has to prioritise either hot water or heating and is unable to do both simultaneously Is this the case? If so this is inconvenient particularly the morning when showers are required. Please advise.
Hi David – with a system boiler this really shouldn’t be the case since the system is pressurised to mains pressure.
If he had installed a combi boiler this would have been an issue.
Why would you want to install an unvented mains pressure water system when you can get the same results from a vented mains water system, but with none of the expense or risks (danger) associated with using an unvented system?
You do yourself no good by publishing a website that is carrying outdated information.
Hi Mike, unvented are extremely popular nowadays because the flow is much better because it comes out at mains pressure where as the vented systems are gravity fed. If people are installing new systems from scratch then we would always suggest an unvented system over a heat only vented system – the cost is not that much more and they have a huge number of safety features (installers need additional accreditation).
Please also let us know which information is outdated and we will look to update it.