Vaillant boilers reviewed: what the guarantee actually says

Vaillant sit alongside Worcester Bosch as the brand most UK installers will name if you ask them what they would put in their own house. The engineering is well thought of, the parts are widely stocked, and most Gas Safe engineers around Northampton and Milton Keynes have worked on them for years.

So this is not a review of whether the boilers are any good. They are. This is a read of the thing that actually varies between two quotes for the same appliance, and the thing almost nobody reads: Vaillant's own published guarantee terms.

The headline number on a Vaillant is not one number. It is a ladder, and where you land on it depends on your installer as much as on the boiler.

The guarantee ladder, as Vaillant publish it

Vaillant publish three columns for each model: the standard guarantee, what it becomes when a myREWARDS registered installer registers it, and what it becomes when that installer also fits a Vaillant filter.

• ecoTEC plus: 5 years standard, up to 8 years when registered by a myREWARDS installer, 10 years with a Vaillant filter.
• ecoTEC exclusive: 5 years standard, up to 8 years registered, 10 years with a Vaillant filter.
• ecoFIT pure: 2 years standard, 7 years registered, 10 years with a Vaillant filter.
• ecoTEC pro: 2 years standard, 7 years registered, and still 7 years with a filter.

Source: Vaillant guarantee information, domestic boiler guarantees

Read the words "up to" carefully

That "up to 8 years" on the ecoTEC plus and exclusive is doing real work. Vaillant's own footnote says the 8 year rung is only available to installers who are Renewable Partner or Platinum myREWARDS members. Silver and Gold members can offer up to 7.

So two installers can quote you the identical ecoTEC plus, both be entirely honest, and one of them can register a longer guarantee than the other purely because of where they sit in Vaillant's loyalty scheme. Nothing about the boiler on your wall is different.

There is a second thing hiding in that table. The ecoTEC pro is the only model where fitting a Vaillant filter does not buy you a longer guarantee. If somebody quotes you a pro with a filter and describes the filter as the route to ten years, that is not what Vaillant publish.

The question to ask is therefore not "is it a Vaillant". It is: which model, which myREWARDS tier are you, which filter, and what guarantee length will be registered against my serial number.

The 30 day rule, and why it is harsher than most

Vaillant's terms say the guarantee must be registered within 30 days of installation, and that failure to register within that period results in the guarantee reverting to 12 months from the date of installation.

That is worth reading twice. It does not drop to the standard 5 years or the standard 2 years. It drops to one year. A missed administrative step on a boiler bought largely for its ten year guarantee leaves you with twelve months.

Registration needs the full 28 digit serial number of the appliance, and for the extended guarantee the 28 digit serial number of the boiler protection kit as well. Both are on the products.

Settle who is doing it before the engineer leaves, and then check it has been done. If it is your installer registering it, ask for confirmation in writing. If it is you, do it that week.

Source: Vaillant domestic boiler guarantee terms and conditions

When the clock starts, and the paperwork that decides it

The guarantee runs from the date of installation, but Vaillant require proof to accept that date: an invoice or a completed Benchmark logbook. Without it, the terms say the guarantee commences from the date of manufacture shown on the boiler data plate.

That is a genuine loss of cover for a paperwork failure. A boiler that sat in a merchant's yard for months before it reached your wall could quietly have burned through a chunk of its guarantee before it was ever switched on.

There is a matching condition at the front of the terms: installation and commissioning must be carried out within 6 months of the boiler being despatched from Vaillant's warehouse. So it is entirely fair to ask how old the unit going on your wall is.

Keep the invoice and the completed Benchmark logbook together, on site. The logbook has to be available for inspection during an engineer's visit, and the annual service has to be recorded in it.

What the ten year rung actually asks of you

This is the section that is missing from every other page about Vaillant guarantees, and it is the one with ongoing obligations attached.

To hold the ten year extended guarantee, Vaillant's extended terms require a Vaillant boiler protection kit, the system flushed, cleansed and inhibited in accordance with BS 7593, and a suitable corrosion inhibitor introduced as described in the manufacturer's instructions.

Then it keeps going after the install day. The pH level must be as per the manufacturer's instructions at all times, and a litmus test kit is supplied to confirm it, with the result written into the Benchmark logbook at each annual service. System cleanliness is confirmed using a turbidity tube. And the strength of the inhibitor must be checked every two years, action taken if needed, and that noted in the logbook too.

None of that is unreasonable. It is just very specific, and it is a standing requirement rather than a one off. If your annual service does not include the inhibitor check and the logbook entry, the extended guarantee is being quietly eroded while you pay for servicing.

Source: Vaillant extended boiler guarantee terms and conditions

What the guarantee does not cover

Broadly similar to other manufacturers, but four of these are worth knowing before you need them.

• Failures caused by contaminated water, including blockages, flux residues, iron oxides, limescale and sludge. Vaillant state the engineer's visit becomes chargeable in that case. This is exactly why the flush and the filter are not an upsell.
• Non genuine spare parts. Vaillant's terms say the use of any non genuine Vaillant spare part in any repair will invalidate the guarantee. Worth remembering if a cheap independent repair is tempting in year three.
• Self maintenance tasks: re pressurising the system, bleeding air, thawing a frozen condensate pipe. Call an engineer out for those and it is not a guarantee visit.
• Moving the boiler to another property without Vaillant's written consent, which invalidates the guarantee outright.

Two smaller things in the small print

A repair does not extend the term. The terms are explicit that the guarantee on any repair or replacement part, including a replacement boiler if it comes to that, does not extend the guarantee period beyond the original term.

And a deposit may be asked for. Vaillant's terms state that for calls to boilers within the guarantee period a refundable deposit may be required before any works or visit, refunded if the diagnosed fault is covered. It is not a charge, but it is a surprise if nobody warned you.

Where Vaillant is not the obvious answer

Two situations, honestly.

The first is where the model on the quote is an entry model rather than the range everybody is thinking of. The reputation Vaillant have is built largely on the ecoTEC plus. A pro is a different proposition with a different standard guarantee, and it should be compared as such rather than as "a Vaillant".

The second is where the installer quoting is not in the right loyalty tier and cannot register the guarantee length you are being sold on. That is not dishonesty, it is just a fact about their account, and the only way to find out is to ask.

And as always: a ten year guarantee that requires a documented annual service, a recorded pH test and a two yearly inhibitor check is a ten year guarantee only if all of that keeps happening. Skip three services and you have something much shorter.

Five questions before you sign

Ask every installer the same five and the quotes become comparable.

• Which Vaillant model exactly, and which filter exactly, by name?
• What is your myREWARDS tier, and what guarantee length will actually be registered against my serial number?
• Are you registering it within 30 days, or am I?
• Is the system being flushed and inhibited to BS 7593, and is that in the price?
• Will the annual service include the pH test and the inhibitor check, recorded in the Benchmark logbook?

The short version

Vaillant deserve their reputation, and on the right model the guarantee is among the strongest available. It is also tiered by installer, conditional on a specific filter, dependent on paperwork filed within 30 days, and reliant on servicing that records things most annual services do not.

Get the model, the filter, the myREWARDS tier and the registered guarantee length written on the quote, then compare it against the other quotes on exactly that basis. We can arrange quotes from Gas Safe registered installers covering Northampton and Milton Keynes if you want to see it done properly.