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Vaillant ecoFit Pure 835 Combi Boiler – Review

In today’s review, we’ll focus on the Vaillant ecoFit Pure 835 combination boiler, a highly efficient boiler from Vaillant’s ecoFit Pure range.

Due to Vaillant’s high-quality German engineering, boilers such as the Pure 835 are not only highly efficient but also the ideal choice for small to medium-sized properties. Established in 1874 in Germany, Vaillant is the second largest manufacturer of boilers in Europe and in direct competition against Worcester Bosch.

Let’s take a look at the features available with the ecoFit Pure 835.

Will the Vaillant ecoFit Pure 835 be suitable for my home?

The 835 is suitable for homes with up to 3 bedrooms and 2 bathrooms with one non-electric shower or bath. To find the right boiler for your home, the number of radiators should be your first port of call as it determines which boiler will be able to supply enough hot water. In the case of the ecoFit Pure 835, you’ll have a sufficient flow rate for up to 20 radiators. To ensure your central heating and hot water runs efficiently, the Pure 835 offers a central heating output of 26.7kW and hot water output of 35kW. For efficient water flow, the ecoFit Pure 835 offers a flow rate of 14.4l/m, which will be powerful enough to either run a shower or a bath (just not at the same time). However, to make sure a combi boiler will be the right fit for your home, it’s essential to double check that your mains water pressure is powerful enough.

To heat up to 10 radiators, the ecoFit Pure 825 is a better fit due to its lower flow rate. Otherwise, the ecoFit Pure 830 is the middle child of the ecoFit Pure range due to its ability to run up to 15 radiators.

Vaillant combi boiler controls

The Vaillant ecoFit Pure 835’s controls are, well, what you’d expect from a standard combination boiler. The control panel on the front of the boiler consists of a few buttons to increase or decrease the output of the boiler and switch the boiler on or off. Let’s face it; you’re probably not going to need to do much with the control panel. However, the display that’s installed will show any error codes, and the running temperature of the boiler, so you can make sure everything’s running as it should be. Due to the modern improvements made to the design and build of boilers, they’re now built to last longer, while being easier to repair.

To take full advantage of your ecoFit Pure 835 combi boiler, Boiler Plus was introduced in April 2018 to ensure that all homes have time and temperature controls installed at the minimum for their boiler. The aim of Boiler Plus is to improve the energy efficiency of homes nationwide by installing high energy-efficiency rated boilers with the appropriate controls.

For combination boilers, there are four additional requirements that will need to be met by the homeowner to be compliant with Boiler Plus. The requirements are as follows:

  • Weather compensation – Water temperature is altered from the boiler based on the outdoor temperature.
  • Load compensation – Water temperature is altered from the boiler based on the current room temperature.
  • Smart control – A type of control that provides automation and optimisation for your boiler
  • PFGHRD (Passive Flue Gas Heat Recovery Device)

Vaillant offers a wide selection of mechanical to smart thermostats to control your heating. Mechanical thermostats are the most basic type of boiler control, which consist of a small dial to turn your heating up or down. Programmable (also known as digital) thermostats are a small step up due to their scheduling features to switch your boiler on or off across a week. However, you may experience some small limitations to the scheduling features available.

To bring your thermostat game to the next level, you could also consider installing a smart thermostat. Vaillant offers their entry into the smart thermostat market with the vSMART, although it is compatible with a range of other smart thermostats such as the Nest or Hive. A smart thermostat provides control via a smartphone app to monitor your energy use and control when your heating is switched on or off, as well as setting temperatures.


The Vaillant ecoFit Pure 835 is one of the most compact combination boilers on offer from Vaillant, measuring a reasonable 700 x 390 x 295mm. Due to the compact nature of this boiler, the ecoFit Pure 835 is a great fit for a standard kitchen cupboard or a cloakroom. If you’re looking for alternative compact boilers, Worcester Bosch also offer their own compact boiler range with the Greenstar Si Compact.

Vaillant ecoFIT warranty

Each Vaillant boiler within the ecoFit Pure boiler range comes bundled with a 5-year warranty, which can be extended by a further 5 years if a Vaillant Advanced Installer registers the installation. With us, you’ll receive a 5-year warranty free of charge with your boiler installation that can be extended by a further 5 years for an extra charge.

Energy efficiency

The ecoFit Pure 835 lives up to its “eco” name with an outstanding ErP (Energy-related Products) rating of 94%, which is an A-grade for efficiency. So with this boiler, you can expect to see a reduction in your energy bills, as well as a reduced carbon footprint relatively soon, although energy savings will always depend on the boiler you currently have.

So what’s this ErP rating? The ErP was introduced by the EU in September 2015 to test energy products (including boilers) before they’re available on the market. Each boiler will need to pass certain criteria for efficiency, performance and build quality. If an energy product fails the tests, the directive steps in and recommends a list of improvements to be made.

Verdict – Is this Vaillant boiler the one for you?

After a closer look at the Vaillant ecoFit Pure 835, we were impressed by the boiler’s incredible energy efficiency and upper-tier build quality. For longevity, this boiler should be a go-to for any homeowner looking for a long-lasting boiler that’s powerful, reliable, and efficient. If you’re looking to replace your old boiler with a new combi, the 835 is a fantastic choice. In addition to high energy efficiency, the ecoFit Pure boiler range has been awarded the QuietMark for reduced-noise design.

If the Vaillant ecoFIT Pure 835 combi gas boiler has sparked your interest, we offer this boiler complete with installation and an extended warranty along with a Honeywell free smart thermostat.

 Vaillant ecoFit Pure 835
ErP rating (energy efficiency)A (94%)
Size (HxWxD in mm)700x390x295
Heating output (kW)26.7
How water output (kW)35
Flow rate (litres/min)14.4
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)25, 30

Which? boiler review

The consumer group Which? review each boiler on the market to find the most (and least) reliable boilers according to a survey completed by thousands of boiler owners. In each review, Which? supply a brand score percentage and star ratings for each category. Take a look at the Vaillant ecoFit Pure 835 ratings below:

Which? Score 
Efficiency rating★★★★★
Brand reliability★★★★☆
Brand customer score★★★★★
Ease of repair★★★★★
Ease of service★★★★★
Availability of parts and spares★★★★★
Build quality★★★★★
Engineer recommendation★★★★★
Brand score80%

Boiler manual

Vaillant ecoFit Pure 835 Combi boiler manual

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