Megaflo repair across London
We repair new and old Megaflo cylinders and boilers. Ring us, day or night.
- Megaflo cylinders and boilers serviced
- All our engineers are Gas Safe registered
Makes we repair
How does booking a Megaflo repair work, and what does it cost?
Booking: ring us any time, day or night, or send your details and we ring you back. We'll ask what the cylinder or boiler is doing, and its model and any code on the display if you can see them. You don't need to know what's wrong. Finding the fault is the engineer's job. Then we tell you when an engineer can come, anywhere in Greater London.
What it costs: a repair's price depends on the part it needs, how long the job takes and when it's done. Our rates are higher in the evening, overnight and at weekends. Once the engineer has found the fault, the rate for the repair is agreed in writing before any work starts.
What happens on a Megaflo repair visit?
A repair visit has three stages.
1. Before anything is touched
The engineer covers the floor around the cylinder or boiler and asks what you have seen and heard since you rang.
2. Finding the fault
The engineer tells you which part has failed, whether they have it with them or must order it, and how long the work should take. No work is done until you say yes.
3. The repair
The engineer fits the part and checks the cylinder or boiler runs as it should before leaving. The repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
What goes wrong on Megaflo cylinders and boilers most often?
The faults Megaflo's own cylinder manuals chart are water at the tundish, hot taps running cold and no flow at the taps. For the boilers, Baxi's guide to the Compact System names low pressure and a frozen condensate pipe as the two you can put right yourself.
- Water at the tundish. The water may drip now and then, run all the time or come out very hot. Each has its own cause, and very hot water or steam is the urgent one.
- Hot taps running cold. The immersion switched off or its cut-out tripped, the programmer, the boiler, the cylinder's own cut-out, or the motorised valve.
- An expansion charge running down. On an Eco, the air gap needs recharging from time to time. On an Essential, the internal expansion wears in normal use. Cold water at the tundish, on and off, is the sign.
- Scale. All the water in Thames Water's region is hard, and Megaflo's guarantee doesn't cover damage from scale. The immersion heater is descaled at the yearly service.
- Low pressure on a Megaflo boiler. E118, which the boilers' guides show you how to put right by topping up.
- A frozen condensate pipe. On a Compact System, Baxi's guide pairs it with E133, a code that has other causes too. The guide points to Baxi's video on thawing it.
- Milky water and a surge at the tap. Both are normal on a Megaflo cylinder, and the milky water clears.
Whichever it is, we'll ask what the cylinder or boiler is doing when you ring. Each Megaflo cylinder fault, by what you see.
Sources: the fault charts in Megaflo's Eco, Essential and Main cylinder manuals, Baxi's cylinder guarantee terms, Baxi's quick start guide for the Megaflo Compact System and Thames Water's page on hard water.
Worth knowing
A Megaflo cylinder is not a boiler. It has no display, no code, no reset button for you and no pressure gauge to top up. Its faults show at the tundish or the taps. The Megaflo boiler is Baxi's gas system boiler of the same name, and it shows fault codes on its display.
Megaflo system boiler codes and what they mean
Megaflo system boilers show a fault as a number beside an error symbol.
- On a Compact System and in Baxi's code list, the code shows as E and the number, such as E118.
- On a GA, the number shows alone, flashing, so E118 there shows as 118.
R beside the code means you may reset it, and a spanner means it needs an engineer. A Megaflo cylinder shows no code at all.
The causes below are from Baxi's installation and service manual for the Megaflo 2 System Compact GA, in its order. Baxi's code list for its older boilers covers the Compact System and the Megaflo System with other Baxi ranges. The list has six of these seven codes, and E117 isn't on it. Baxi's manual says a code that a reset doesn't clear, or that keeps coming back, needs looking into.
A cylinder's faults show by what you see instead. Megaflo cylinder faults, from the tundish to the taps.
E118Megaflo E118 (not E119): the water pressure is too low
What it means: E118 means the water pressure in the heating has fallen below 0.5 bar, and the boiler has stopped. The code means the same on the GA, the Compact System and the Megaflo System. Low pressure on a Megaflo boiler is E118. E119 is the low-pressure code on some other Baxi boilers, such as the Platinum.
Possible causes, as the manual lists them:
- the pressure itself, out of range
- if the pressure is in fact right, the pressure sensor's supply at the main board, the pressure sensor, or the board
What you can do: top up the pressure. On a GA, the user guide shows how:
- Connect the filling loop's hose.
- Open one tap fully.
- Open the other slowly while watching the gauge under the boiler.
- Close both at 1 bar or more.
- Take the hose off.
On a Compact System, Baxi's quick start guide lists E118 as a fault you can put right yourself, with its video on topping up. If E118 comes back, or the pressure keeps falling, ring us. We'll ask what the gauge reads.
E133Megaflo E133: the gas supply was interrupted, or the flame didn't light or wasn't detected
What it means: E133 on a Megaflo boiler means the gas supply was interrupted, the ignition failed or no flame was detected. Baxi's manual for the GA gives that meaning, with E134 and E135 as its close relations.
Possible causes, as the manual lists them:
- No spark at the electrodes: the ignition electrode, its lead and the main board.
- A spark but no flame: the gas reaching the burner, then the gas valve and its wiring.
- A flame that goes out after a few seconds: the gas pressure at the valve, the valve's setting and the flame sensing electrode.
On a Compact System in a frost, a frozen condensate pipe is a possible cause too. Baxi's quick start guide pairs E133 with it, as the boiler shuts down to protect itself when the pipe outside freezes. The code still means a gas, ignition or flame fault, whatever caused it.
What you can do:
- See whether the other gas appliances in the home work, and whether a prepayment meter has credit.
- If there is no gas, contact the gas supplier, as Baxi's guide says.
- On a Compact System in a frost, thaw the condensate pipe as Baxi's guide shows, then reset.
If E133 comes back after a reset, ring us, and leave the boiler off. We'll ask whether the cooker or another gas appliance works.
Every cause of E133 on Baxi's boilers, and what fixes it, is on the E133 fault code page.
E110Megaflo E110: the safety thermostat has tripped, from overheating
What it means: E110 means the heating water has overheated and the safety thermostat has tripped, in Baxi's manual for the GA. Baxi's code list for the Compact System and the Megaflo System adds a second trigger, the temperature rising too fast. The list suggests a jammed pump or air in the system may cause that.
Possible causes, as the manual lists them:
- a fault in the heating system, put right and the boiler left to cool
- the safety thermostat itself
- the main board, or the flow and return sensors
What you can do: press R once, as the user guide says. If E110 comes back, ring us. Baxi's guide says a boiler whose fault won't reset by hand mustn't be used until a competent person has put it right. We'll ask what the boiler was doing when it stopped.
E125Megaflo E125: the heating water isn't circulating
What it means: E125 means the water isn't moving round the boiler's heating circuit properly, in Baxi's manual for the GA. The boiler shows it when the water's temperature doesn't rise just after the burner lights, or twice runs well past its setting soon after lighting.
Possible causes, as the manual lists them:
- air in the boiler or the system, which must be fully vented
- the flow sensor's connections, its position or the sensor itself
- the pump, its power supply, or the main board
What you can do: one reset, which the manual allows. Baxi's user guide for the GA gives no other step. If E125 comes back, we'll ask whether the radiators are warm when you ring.
Every cause of E125 on Baxi's boilers, and what fixes it, is on the E125 fault code page.
E117Megaflo E117: the water pressure is too high
What it means: E117 means the heating's water pressure is above 2.7 bar, in Baxi's manual for the GA. The GA's user guide adds that above 3 bar the safety relief valve opens. E117 isn't on Baxi's code list for the Compact System and the Megaflo System.
Possible causes, as the manual lists them:
- the pressure itself, out of range
- if the pressure is in fact right, the pressure sensor's supply, the sensor or the main board
What you can do: nothing at the boiler, beyond the user guide's rule that the filling loop is never left connected. Baxi's user guide sends E117 to an installer. We'll ask what the gauge reads when you ring.
E128Megaflo E128: the flame went out while the boiler was running
What it means: E128 means the boiler lost its flame while it was running, and the boiler stops until it is reset. The code means the same on the GA, the Compact System and the Megaflo System.
What you can do: one reset, which the manual allows. If E128 comes back, it needs an engineer, as the GA's user guide says. We'll ask how often it has happened.
E160Megaflo E160: the fan or its wiring
What it means: E160 means a fault in the fan or its wiring. The code means the same on the GA, the Compact System and the Megaflo System.
Possible causes, as the manual lists them:
- the fan's plugs, at the fan and at the main board
- the mains voltage at the board's fan connector
- with power there, a jammed fan or faulty wiring
- with no power there, the board
The manual sends a fan that doesn't start, or doesn't reach its speed, to the same checks.
What you can do: nothing at home. E160 isn't among the codes Baxi's manual lets you reset. We'll ask whether a spanner shows beside the code when you ring.
MoreEvery other Megaflo boiler code, in one list
Every other code in Baxi's manual for the Megaflo 2 System Compact GA, with 321 from its user guide. Most causes are for an engineer to check, and the manual allows a reset where the list says so.
09The gas valve's cable has a fault
Possible causes
A reset is allowed. If it keeps coming back, the main board's connections, then the board
15The gas valve has a fault
Possible causes
As for 09, a reset, then the main board's connections and the board
20The heating flow temperature sensor has a fault
Possible causes
The sensor's position and wiring, then the sensor
28The flue temperature sensor has a fault
Possible causes
The sensor's checks, then the sensor
40The heating return temperature sensor has a fault
Possible causes
The sensor's position and wiring, then the sensor
55The boiler needs calibrating
Possible causes
Shown after its data stick is replaced. The engineer runs the calibration
109A pre-circulation fault
Possible causes
An engineer's check
130The flue sensor has tripped, as the flue is too hot
Possible causes
The sensors. If the pump runs, a blocked heat exchanger
134The gas valve was open too long without a flame
Possible causes
A reset is allowed
135The gas supply was interrupted (an internal error)
Possible causes
A reset is allowed
154The flow and return sensor test failed
Possible causes
An engineer's check
270A circulation fault, the boiler heating with no water moving
Possible causes
An engineer's check
321The hot water sensor has a fault (in the user guide's list)
Possible causes
An engineer's check
384A flame is sensed when there should be none
Possible causes
A reset is allowed. If it keeps coming back, the main board's connections, then the board
The Compact System and the Megaflo System: the codes on Baxi's list that differ
The codes below come from Baxi's code list for its older boilers. The list covers the Megaflo Compact System and the Megaflo System with other Baxi ranges, and not every boiler shows every code. Most of its codes mean what they do on the GA. The others are below, and E55 and E117 aren't on the list.
E10The outside sensor has a fault
Possible causes
The outside sensor
E12, E13The water flow switch is stuck open, or stuck closed
Possible causes
The flow switch
E50The hot water sensor has a fault, on a boiler with a cylinder
Possible causes
The hot water sensor
E83 to E87A communication fault
Possible causes
An engineer's check
E103, E104The Safety Assist battery is flat, or the Safety Assist board is faulty
Possible causes
The battery, or the board
E107The boiler's boards are out of step
Possible causes
An engineer's check
E129The flame was lost more than once during calibration
Possible causes
An engineer's check
E317 or 162The mains frequency is wrong
Possible causes
The electricity supply
E321 or 163The hot water sensor is short-circuited or open-circuited
Possible causes
The hot water sensor
E385 or 165The supply voltage is too low
Possible causes
The electricity supply
E430 or 166A temporary water pressure fault. With the flame symbol crossed out, the water pressure test failed
Possible causes
The water pressure
Baxi's other boilers use many of the same numbers. Every make's fault codes, explained code by code.
Sources: Baxi's installation and service manual for the Megaflo 2 System Compact GA (7206338-09, 2014), its user's operating instructions (7206339-07, 2013), Baxi's code list for its older boilers and Baxi's quick start guide for the Megaflo Compact System (7849761), read on 10 October 2026.
Which Megaflo do you have: a cylinder, a system boiler or both?
Megaflo is two things with one name, and a home may have one of each:
- Megaflo unvented hot water cylinders, a brand of Baxi Heating UK
- Baxi's Megaflo system boilers, gas boilers built to heat a separate cylinder
A Megaflo cylinder has no display and shows no code. A Megaflo system boiler shows a fault code on its display. We'll ask which you have, and what it is doing, when you ring.
Not every sign is a fault.
- On a GA, Sd shown in turn with the boiler's temperature means a service is due.
- The numbers 00 to 08 under a GA's information button are readings, such as temperatures and the pressure.
- After a refill, a GA's pump may run for up to 10 minutes to clear air.
- On a Megaflo cylinder, milky water and a small surge when a hot tap first opens are normal.
Megaflo cylinder faults: what you see and what it means
Megaflo cylinder faults show by what you see, as the cylinder has no display:
- water at the tundish, the open funnel on its discharge pipe
- hot taps running cold
- no flow at all
The causes here are from the fault charts in Megaflo's cylinder manuals, and the steps for you are Megaflo's own. Megaflo leaves the cylinder's cut-outs, relief valves, thermostats and expansion recharge to a competent person, so the steps for you stop short of the cylinder.
Megaflo's manual also warns against switching the cylinder on while the water in it may be frozen, and against ever bypassing its thermal cut-outs.
Sources: the fault charts, maintenance sections and user instructions in Megaflo's Eco, Eco Plus, Essential and Main cylinder manuals.
Who may work on a Megaflo cylinder?
Work on a Megaflo cylinder is for a competent person for unvented systems, in Megaflo's own manuals.
- Servicing, and any work on the cylinder and its controls: someone competent to install and maintain unvented hot water systems.
- Electrical work: a competent electrician.
The manuals ask for the cylinder to be installed to Building Regulation G3 in England and Wales. Megaflo's own FAQ advises householders to check that their installer holds a G3 unvented qualification.
Our engineers hold the G3 unvented qualification for the cylinders, and all our engineers are Gas Safe registered for the Megaflo boilers' gas work. We'll ask which Megaflo you have when you ring.
Megaflo is one of several makes of unvented cylinder. Unvented cylinders of every make, and who may work on them.
How do you reset a Megaflo?
Resetting a Megaflo depends on which one you have.
A Megaflo cylinder has no reset for you. Each cut-out's reset button sits behind a cover that needs the electricity off, in the installer's part of Megaflo's manual. A tripped cut-out means the water once got too hot, so ring us.
A Megaflo system boiler resets at its button, as Baxi's papers show:
- Megaflo Compact System: press and hold the reset button for 5 seconds.
- Megaflo 2 System Compact GA: press R, when R shows beside the code, and hold it for 1 to 3 seconds. A code shown with a spanner isn't one to reset.
Baxi's guides set no number of tries. If a reset doesn't clear a code, or the code keeps coming back, Baxi's manual says it needs looking into.
The pressure on a GA is normal at 1 to 2.5 bar. Below 1 bar, its user guide shows how to top up at the filling loop. Close both taps at 1 bar or more, and take the hose off afterwards. Above 3 bar, the safety relief valve opens and E117 shows.
On a Compact System, E118 means the pressure needs topping up, and Baxi's quick start guide points to its own video for it. A Megaflo cylinder has no gauge to top up. It runs at the pressure its reducing valve sets.
A frozen condensate pipe is one possible cause of E133 on a Compact System, which Baxi's guide pairs with that code. E133 has other causes too. A frozen pipe can be thawed with warm, never boiling, water, where it is at ground level and easy to reach. Then reset once. When a boiler won't fire up, and frozen condensate pipes.
Sources: Baxi's quick start guide for the Megaflo Compact System, Baxi's installation and service manual and user's operating instructions for the Megaflo 2 System Compact GA, and Megaflo's cylinder manuals.
Is your Megaflo still under guarantee?
Megaflo's guarantee depends on the range. Each cylinder has a standard guarantee and a longer one on its stainless steel inner tank:
- Eco: 2 years, and 30 years on the inner tank.
- Eco Plus: 2 years, and 30 years on the inner tank.
- Essential: 2 years, and 20 years on the inner tank.
- Essential for heat pumps: 2 years, and 10 years on the inner tank.
- Main: 1 year, and 20 years on the inner tank.
Each range's guarantee needs:
- the cylinder registered within 30 days of fitting
- the Benchmark checklist filled in
- a service every year by a competent person, with proof of it
Damage from scale or frost isn't covered, nor tampering with the factory-fitted temperature and pressure relief valve. While a cylinder's guarantee runs, Baxi's own engineers repair it. Baxi doesn't pay another engineer's bill unless it agreed in writing first.
On the Essential, Megaflo's manual says the internal expansion wears in normal use. If it then needs recharging more often during the guarantee, Baxi will fit external expansion parts or replace the cylinder, under its terms.
The Megaflo Compact System boiler has 7 years on parts and labour, on Baxi's terms:
- registered within 30 days
- the Benchmark checklist filled in
- the boiler and its filter serviced every year by a Gas Safe engineer, within 60 days of the anniversary
- the system cleaned, a magnetic filter fitted and the water treated before it went in
The GA came with a first year, and a second year free when it was registered with Baxi. Its guarantee asked for a service every 12 months by a Gas Safe registered engineer. Repair costs from another engineer that weren't agreed in advance aren't covered. Baxi's boiler terms also leave out a boiler repaired or serviced with parts that aren't Baxi's own.
A cylinder or boiler still under its maker's guarantee is usually repaired by the maker, at no charge, so ring Megaflo first. Once the guarantee has ended, or for a fault it doesn't cover, ring us. We are an independent firm, with no connection with Megaflo.
What does a Megaflo service cover?
A Megaflo cylinder needs a service every year by a competent person, in Megaflo's manuals. The Main's manual times it with the boiler's. The service covers:
- The relief valves. Each is opened by hand, to see the water runs freely to the tundish and the valve reseats.
- The strainer in the pressure reducing valve, washed.
- The immersion heater, taken out and descaled, with a new gasket.
- The air gap or the expansion vessel, recharged.
- The seals, checked, with the Benchmark service record filled in.
A Megaflo boiler needs its own yearly service. On a GA, Sd on the display after 11 months means it is due. On a Compact System, Baxi's guarantee asks for the boiler and its filter to be serviced every year by a Gas Safe engineer. Each service is due within 60 days of the anniversary of the boiler's fitting.
We service every Megaflo model, and give you the rate on the call.
Do you cover my part of London?
Yes: we travel all over Greater London, day and night, to repair Megaflo cylinders and boilers in every borough, north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
The other makes we repair
Every main make, combi, system and regular. Pick yours for its common faults, its codes and how we repair it.
Questions about Megaflo cylinders and boilers
Do I need to know what's wrong with my Megaflo before I ring?
No. Ring and say what the cylinder or boiler is doing, or what you can see or hear, and we'll ask the rest. Finding the fault is the engineer's job.
Do you charge more in the evening or at weekends?
Yes. Our rates are higher in the evening, overnight and at weekends.
Can you repair an older Megaflo?
Usually, yes. It depends on the cylinder or boiler's condition and whether its parts are still made. We'll ask for the model when you ring.
Will a repair affect my Megaflo guarantee?
While a Megaflo guarantee runs, ring Megaflo, as its own rules decide who repairs it:
- Megaflo's manuals send cylinder repairs to Baxi's own engineers.
- Baxi doesn't pay another engineer's bill unless it agreed in writing first.
- Baxi's boiler terms leave out a boiler repaired with parts that aren't Baxi's own.
Once the guarantee has ended, or for a fault it doesn't cover, ring us. Our engineers hold the G3 unvented qualification for the cylinder, and are Gas Safe registered for the boiler.
Do you fit Megaflo's own parts?
Yes, the maker's own parts wherever they are available. Each repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
How much does a Megaflo repair cost?
The cost of a repair depends on the part, how long the job takes and when it's done. The rate is agreed in writing before the repair starts. How our rates work.
Is a Megaflo a boiler?
A Megaflo cylinder isn't a boiler. It is an unvented hot water cylinder, fed from the mains and heated by a boiler or by immersion heaters. It shows no fault code. Baxi also sells Megaflo system boilers, gas boilers built to heat a separate cylinder, which show fault codes on a display. A home may have one of each, so we'll ask which is giving trouble when you ring.
Hot water is coming from the tundish: what should I do?
Hot water or steam from the tundish means the cylinder's thermal controls have failed, Megaflo's manual says, and the water will be very hot.
- Switch off the immersion heater.
- Shut down the boiler.
- Leave the water supply on.
- Touch none of the valves.
- Ring us straight away.
Can I reset or top up a Megaflo cylinder myself?
A Megaflo cylinder has nothing for you to reset or top up.
- Its cut-outs reset behind a cover, with the power off.
- Recharging its air gap or expansion vessel is maintenance for a competent person, in Megaflo's manuals.
- It has no pressure gauge to top up.
A Megaflo system boiler is different. Baxi's guides show how to top up its pressure and reset it. For the cylinder, ring us.
Who makes Megaflo?
Megaflo is a brand of Baxi Heating UK, whose parent company is BDR Thermea. Baxi says Megaflo carries on as a specialist brand of its own. Heatrae Sadia, another of Baxi's brands, also offers Megaflo cylinders, and the older Megaflo Eco Plus manual carries its name. We are independent of all three. Baxi boilers: their codes and repairs.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
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A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
