Buyer's Guide

Vaillant Boiler Buyer's Guide

Three steps to choosing the right Vaillant boiler for your home – plus an interactive quiz for a personalised recommendation.

Step 1 of 3

Understand Your System Type

Before choosing a boiler model, you need to know which type of heating system is right for your property. There are three main types in the UK.

Combi Boiler

A combination boiler provides both central heating and domestic hot water directly from the mains, with no need for a separate hot water cylinder or cold water storage tank. It heats water on demand as you open a tap.

Best for: Smaller properties (1–3 bedrooms), households with one bathroom, and properties with limited storage space. Not suitable where high simultaneous hot water demand is required.

Vaillant options: ecoTEC plus Remastered, ecoTEC exclusive, ecoTEC pro, ecoFIT pure

System Boiler

A system boiler heats your central heating circuit directly and feeds a separate hot water storage cylinder. The cold water supply comes from the mains, but the hot water is stored and available in volume for simultaneous use across multiple outlets.

Best for: Medium to large properties (3–5 bedrooms), households with two or more bathrooms, and properties where high simultaneous hot water demand is a regular requirement.

Vaillant options: ecoTEC plus Remastered, ecoTEC exclusive, ecoTEC pro, ecoFIT pure

Open Vent (Regular)

A conventional or open vent boiler works with a traditional gravity-fed system, characterised by a cold water storage tank in the loft and a feed-and-expansion cistern. It feeds a separate hot water cylinder.

Best for: Older properties with existing open vent pipework where conversion to a sealed system would be costly or impractical. Also suitable where a large hot water storage volume is needed.

Vaillant options: ecoTEC plus Open Vent

Not sure what system you currently have? Look in your airing cupboard or loft. If you have a large copper cylinder and/or tanks in the loft, you likely have a system or open vent setup. If there are no tanks or cylinders, you almost certainly have a combi. Our engineers can confirm during a free survey visit.
Step 2 of 3

Match the Model to Your Home

Once you know your system type, use the property scenarios below to narrow down the right Vaillant model.

Small Property / Flat

1–2 bedrooms, 1 bathroom, modest hot water demand.

Recommended: ecoFIT pure (combi, 25kW) – reliable, efficient, and cost-effective for smaller properties. Or ecoTEC plus Remastered 25kW combi for those wanting premium build quality.

Average Family Home

3 bedrooms, 1–2 bathrooms, moderate hot water demand.

Recommended: ecoTEC plus Remastered (combi 30–32kW or system). The most popular choice in the UK for good reason – outstanding efficiency and reliability for typical family use.

Large Property

4–5+ bedrooms, 2–3 bathrooms, high simultaneous demand.

Recommended: ecoTEC pro (system 35kW+) or ecoTEC exclusive (system). A system boiler with a well-sized cylinder will outperform any combi at high demand. Consider the ecoTEC exclusive for maximum efficiency at scale.

Older / Period Property

Existing open vent or gravity-fed system, loft tanks present.

Recommended: ecoTEC plus Open Vent. Retaining the existing system avoids costly pipework alterations and is often the most practical and cost-effective approach. We can assess whether conversion makes financial sense.

Step 3 of 3

Get a Tailored Recommendation

Answer three quick questions and we'll suggest the best Vaillant model for your home.

Question 1 of 3
How large is your property?

Question 2 of 3
How many bathrooms does your property have?

Question 3 of 3
What is your current heating system type?

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Our recommendation for your home

Book a Free Survey
Understanding Your System

Combi, Unvented & Open Vented — What's the Difference?

Not sure which type of system you have, or which would suit your home? The diagrams below show exactly how each system works and what makes them different.

1
Combination (Combi) Boiler
No cylinder · Instant hot water
GAS MAINS COLD VAILLANT COMBI BOILER FLUE RADIATORS HOT TAP Flow Return

How it works: The combi boiler heats water directly from the mains on demand — no hot water cylinder or cold water tank needed. Central heating and domestic hot water are both served from one compact unit.

  • Best for: Flats, 1–3 bed homes, limited space
  • No cylinder or loft tank required
  • Instant hot water — no waiting
  • Flow rate limited by mains pressure
2
Unvented (System) Boiler
Pressurised cylinder · Mains fed
GAS MAINS COLD VAILLANT SYSTEM BOILER FLUE EXP UNVENTED CYLINDER (Mains Pressure) CH Flow HOT TAP CH Return

How it works: A system boiler heats water stored in a sealed, pressurised cylinder fed directly by the mains. No cold water tank needed in the loft. The sealed system means mains pressure hot water to every tap and shower.

  • Best for: 3–5 bed homes, multiple bathrooms
  • Mains-pressure hot water throughout
  • No cold water tank — just a cylinder
  • Hot water can run out if cylinder is emptied
3
Open Vented (Regular) Boiler
Gravity fed · Cold tank in loft
F&E TANK COLD WATER STORAGE TANK MAINS IN VAILLANT OPEN VENT BOILER GAS FLUE HOT WATER CYLINDER (Gravity / Low P) Cold feed RADS HOT TAP Vent

How it works: A regular boiler feeds from a cold water storage tank in the loft and stores hot water in a separate cylinder. It also has a small feed and expansion tank. This is the traditional British central heating layout.

  • Best for: Older properties, large homes
  • Compatible with existing cylinder & tank setups
  • Lower hot water pressure (gravity fed)
  • Hot water can run out — reheating time needed
Feature Combi Unvented System Open Vented
Hot water cylinder ✓ No Yes (pressurised) Yes (gravity fed)
Cold water tank in loft ✓ No ✓ No Yes
Hot water pressure Mains (high) Mains (high) Gravity (low)
Instant hot water ✓ Yes No (stored) No (stored)
Best suited to Flats · 1–3 bed 3–5 bed homes Older / larger homes
Vaillant model ecoFIT pure · ecoTEC plus ecoTEC exclusive · pro ecoTEC plus Open Vent

Not sure which system you have? Our engineers can identify your system type during a free no-obligation survey.

Ready for a Free Assessment?

Our engineers will visit your property, assess your existing system, and give you a written recommendation and fixed quote – completely free and with no obligation.

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