We install Vaillant and Ideal, so treat this as an installer view rather than an impartial review. What follows is what engineers actually talk about, which is not the same as what the brochures emphasise.

The things that matter more than the badge

• Parts availability. A boiler is only as good as your ability to get a part on a Friday afternoon in January. This matters more than almost anything else and it never appears in a review.
• Warranty length, and what voids it. Most require annual servicing by a competent person. Miss one and you may have nothing.
• Correct sizing. An oversized boiler cycles constantly, which is wear. This is an installer decision, not a brand one.
• The installation itself. A well-installed mid-range boiler outlasts a badly installed premium one. Every time.

Vaillant

What we fit most. Well engineered, parts are widely available, and the engineering is straightforward to work on, which keeps repair costs down over the life of the appliance. We are a Vaillant accredited installer, which gives access to extended warranties not available through a general installer.

Ideal

We install Ideal as well. The Logic and Vogue ranges are widely fitted, parts are easy to source and the price point is generally lower than Vaillant. A sensible choice where budget is a real constraint.

Worcester Bosch

Very widely installed in the UK, with correspondingly good parts availability, and generally well regarded. We repair Worcester Bosch but we are not an accredited installer, so we cannot register their accredited-installer warranties. We would rather tell you that than have you find out later.

Viessmann, Baxi, Glow-worm and the rest

All fit competent boilers. Baxi and Potterton share engineering, as do Vaillant and Glow-worm, which is why some of their fault codes match. Viessmann is well engineered with a smaller UK installer base. We repair all of them.

What we would ask before choosing

1. How many bathrooms, and do two ever run at once? That decides whether a combi is right at all.
2. What is your incoming mains flow rate? A combi cannot deliver more than the mains gives it.
3. Is there a cylinder now, and is removing it the right move?
4. Is the system clean? A new boiler on a sludged system inherits the problem.
5. What is the warranty, and what are its conditions?

Frequently asked questions

Which combi boiler is the most reliable?

Reliability is driven as much by installation, sizing and system cleanliness as by brand. Parts availability matters more than most reviews suggest.

Do you only fit one brand?

We fit Vaillant and Ideal, and we repair all the common makes.

Is a more expensive boiler worth it?

Often, through parts availability and warranty length, but not if it is oversized or fitted to a dirty system.

Is a combi right for my house?

If two bathrooms are ever used at once, or your mains flow is poor, a cylinder may suit you better. See unvented cylinders.

Want it sorted properly?

Anything past the free checks above needs a Gas Safe engineer with the right test kit. Ring Vantage on 01462 506374, any hour, any day of the year. You will get an honest arrival time rather than a comforting one, and the price before the work.