Gas Safe registered
Heatline specialists
Capriz, Vizo, Compact and Monza. Twenty years on Heatline boilers, rates agreed beforehand, parts guaranteed a year.
Answered 24 hours a day by a technical customer service member.
Heatline is a Vaillant Group brand, so the F numbers are Vaillant's F numbers.
No heating or hot water right now? Call 0203 868 6134. We will tell you the earliest realistic slot rather than the one you want to hear.
Add the F number and your postcode and we can usually name the part first.
Three steps, and you will know where you stand before anyone is booked.
A Heatline is a Vaillant underneath, and that changes what your code is worth. Heatline sits in the Vaillant Group beside Vaillant and Glow-worm on a shared platform, so an F75 here means what it means on a Vaillant. The badge reads like an orphan and the engineering is anything but. We are the London firm that tells you whether it is the boiler or the cylinder before anyone attends.
Heatline sits in the Vaillant Group beside Vaillant and Glow-worm, sharing the F numbering, so an engineer who knows that platform knows yours.
The most misdiagnosed code on this platform. The boiler started the pump, did not see the pressure rise it expected, and stopped.
It is not simply low pressure. That is F22, which most householders can clear themselves: fill through the loop cold to between 1 and 1.5 bar, close both valves, reset once. F75 means the change cannot be detected, pointing at the pressure sensor, the pump, or air and sludge preventing flow. Topping up repeatedly draws oxygenated water in, which is how sludge forms, and sludge is what turns an F22 into an F75.
Why owners get stuck: it is intermittent, running faultlessly for days then tripping three times in an hour, which makes a quick look at the board tempting and useless. Testing sensor output against real pressure separates the two.
The boiler lit and then lost the flame. In a London winter the cause is usually the condensate pipe freezing so it cannot discharge. Thaw the white plastic pipe outside with warm water, never boiling. If it happens every cold snap the pipe is too narrow, too long or falls the wrong way, and lagging will not fix routing.
Watch what follows: an F29 clearing into a persistent F75 is common, and the second fault is the real one.
| Code | What it means | What it usually turns out to be |
|---|---|---|
| F28 | Failure to ignite | Gas supply, electrodes, then the gas valve |
| F20 / F24 | Overheat, or heat rising too fast | Circulation. Pump, air or a closed valve |
| F27 | Flame detected when there should be none | Safety critical. Engineer rather than reset |
| F61 / F62 | Gas valve control or shutdown | The valve or its wiring. Not a reset job |
Heatline cover can run from the serial number rather than the day the boiler was fitted. An appliance that sat in a merchant's stock for a year arrives already part way through its guarantee, and owners find out only when they claim. Read us the serial when you ring and we will check it against your fitting date.
Two account for most calls.
Hot water never properly hot, heating faultless. The plate heat exchanger is scaling. The heating circuit is sealed so it scales once and stops; the hot water side takes fresh mains water at every tap. A diverter fault gives none at all. An annual service catches it early.
Struggling to get anyone to look at it? Heatline technical support runs online rather than by phone, which leaves owners stranded and feeds the idea that nobody works on them. The engineering is Vaillant Group.
The badge says budget, the platform says Vaillant
Heatline sits in the Vaillant Group beside Vaillant and Glow-worm, sharing the F numbering. Your code is better documented than the badge suggests, and F75 is the one worth getting right first time.
The label is behind the front panel, and the serial matters as much as the name.
Capriz and Capriz Plus are the ranges most often on London walls, particularly in flats. Vizo, Compact, Monza and the older C24 sit alongside them, all wall-hung condensing combis. Read us the serial when you ring; it matches your appliance to the right parts and settles the guarantee question. We work on every make of boiler.
The big difference between here and further north.
Water here carries roughly 277 milligrams of calcium carbonate per litre, from chalk the Thames and the Lea run through, so the plate heat exchanger scales faster than the manual allows, the same in Blackheath and Greenwich as Wimbledon.
Scale drops out of solution faster the hotter the water gets. A combi delivering taps at 65 degrees furs up its plate heat exchanger faster than one set to 50, which is still hot enough to scald, and turning that dial down costs nothing. It applies to the tap setting, not a cylinder, which must reach 60 degrees.
Age does not decide it. The failed part does.
| What has failed | Under 8 years | 8 to 14 years | 15 years and older |
|---|---|---|---|
| Pressure sensor, thermistors | Repair | Repair | Repair if parts exist |
| Ignition and sensing electrodes | Repair | Repair | Repair |
| Expansion vessel, pump | Repair | Repair | Repair |
| Fan | Repair | Repair | Depends on the rest of the boiler |
| Diverter valve, plate heat exchanger | Repair | Repair | Repair if the part is still made |
| Gas valve | Repair | Borderline, we will be straight with you | Replace |
| Control board | Check the serial first | Usually replace | Replace |
| Main heat exchanger | Guarantee claim if in date | Replace | Replace |
Under eight years old it is a repair without argument, and guarantee cover is worth knowing because cover may have started before delivery. Between eight and fourteen a board or heat exchanger costs roughly what it does on a Vaillant while the appliance is worth less, so replacement wins earlier than on the parent brand. Cheaper repairs stay worth doing, and shared parts help. See boiler replacement and our cost guide.
Most firms here are combi-only, which does not suit a city of large houses.
Heatline build combis, so a cylinder is usually left from an older setup or serving a second circuit. Either way it is a second appliance with its own thermostat, immersion element and, if unvented, its own safety devices. When the hot water goes the boiler takes the blame and is often fine: a cylinder sensor out of its pocket, a failed motorised valve, or a scaled immersion element.
Water at its tundish means a safety device has failed, and is never something to cap. That needs G3 as well as Gas Safe registration and we hold both, so unvented cylinder repair happens on the same visit, and larger houses across Croydon usually get a scale reducer with it.
Local boiler repair specialists
Clear advice. Careful repairs. Family-friendly service.
Call 0203 868 6134North and south of the river.
These are where we work most, not a boundary. An engineer attends anywhere in north London and south London. Tell us where you are and we will say plainly when we can get to you.
If you smell gas: do not touch any switches. Open the windows, leave the property, then call the National Gas Emergency Service on 0800 111 999. That line is free and open 24 hours. Call them before you call us.
If a carbon monoxide alarm is sounding: get everyone out immediately, then call 999 if anyone feels unwell. Do not go back in until the property has been ventilated and checked.
If the boiler locks out repeatedly: try one reset. If it locks out again straight away, stop. Repeated resets hide a fault that is still there, and on a gas appliance that is not a risk worth taking.
Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas appliances. Never open the boiler casing yourself.
Heatline is a Vaillant Group brand, beside Vaillant and Glow-worm, sharing the F code numbering. The platform is common, so an F75 means what it means on a Vaillant and an engineer who knows one knows the other. That matters because the badge reads like an orphan nobody supports. Compare the Vaillant fault codes and the overlap is obvious.
The boiler started the pump and did not see the pressure rise it expected, so it stopped. Not the same as low pressure, which is F22. F75 means the change cannot be detected, pointing at the sensor, the pump, or air and sludge stopping flow. It is intermittent, running fine for days then tripping repeatedly, which is why it gets misdiagnosed. A power flush is sometimes the answer.
The boiler lit and then lost the flame. In a London winter the usual cause is the condensate pipe freezing so it cannot discharge. Thaw the white plastic pipe outside with warm water, never boiling. If it recurs every cold snap the pipe is too narrow, too long or falls the wrong way. Watch what follows, because an F29 clearing into a persistent F75 is common and the second fault is the real one. No heat? See emergency boiler repair.
Reputation rather than reality. Heatline technical support runs online rather than by phone, which leaves owners stranded and feeds the idea that nobody works on them. The engineering is Vaillant Group and parts follow the shared platform, so availability is better than the badge suggests. If quoted a long lead time, ask which part and which supplier was checked. An annual service catches problems early.
Cover runs from the serial rather than the installation date, so an appliance that sat in stock arrives part way through, and owners discover this only when they claim. Read us the serial when you ring and we will check it against your fitting date. If cover has gone it becomes ordinary economics: a board costs roughly what it does on a Vaillant while the appliance is worth less. See our cost guide.
Yes. Heatline build combis, so a cylinder is usually left from an older setup, and it is a second appliance with its own thermostat, immersion element and, if unvented, its own safety devices. Unvented work needs G3 as well as Gas Safe registration and we hold both, so the cylinder is diagnosed on the same visit. A failed cylinder sensor shows no F code. See unvented cylinder repair.
Two makes below share Heatline's platform, which is why the codes look familiar.
No gas supply? Plenty of London flats run without one, so we also cover electric boiler repair.
Give us the F number and the serial from the label. With those two we can usually name the part, and say whether cover applies, before anyone sets off.
Gas Safe registered. Unvented cylinder qualified. Parts guaranteed for a year. Covering London, north and south of the river, 24 hours a day.
