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Liverpool Homeowner's Boiler Buying Guide

The honest, unvarnished walk-through of choosing, sizing and installing your next boiler, from a family that's been on the tools across Merseyside since 1998. Read it cover to cover or jump to your worry. About 35 minutes with a brew.

How to use this guide

There are four kinds of readers who land on this page, and we've written it so all four can get what they need. If you're planning ahead with a working boiler, start at the top and read through. You've got time to do it properly. If your boiler is limping and you suspect a replacement is on the horizon, jump to sizing, then to honest pricing. Those two sections answer most of the worries.
 

If your boiler is dead this week, ring us on 0151 739 8945. We'll get someone out today in most of Merseyside. Then come back to this guide once the heating is on again. If you've already had a quote that doesn't smell right, go straight to "What 'fully fitted' should include" and the eight red flags. Those two sections will tell you what's missing from the quote in front of you.
 

We update this guide every spring. The pricing bands, warranty terms, and brand lineups change, and we'd rather refresh the lot than leave a customer reading outdated information.​

Combi Boiler

Understanding what is right for your home

A combi boiler heats water on demand. No tank in the loft, no cylinder in the airing cupboard. Hot water comes when you turn the tap. One downside: a single combi struggles to feed two showers simultaneously.

A four-question decision tree

1

Unvented Cylinder

Have you got more than one bathroom in regular use? If yes, lean towards a system boiler with an unvented cylinder, such as a Megaflo.

2

Combi

Have you got room in the loft for a tank, or in a cupboard for a cylinder? If neither, a combi is your best bet.​​

3

Combi Again

Do you ever run two showers at the same time? If yes, system over combi, every time.

4

Get A Survey

Is the existing system gravity-fed (open vented), and is converting to mains pressure expensive? If the conversion cost exceeds £1,200, a regular replacement can sometimes be the right call. Get a survey.

If you want a deeper dive into the trade-offs, our post on boiler types explains each one in more detail. Don't trust a tree on a website. The last 20% of this decision needs eyes on. We do free home surveys with no commitment to buy. Book one at ddwilson.com/quick-quote.

Services

The sizing question, and why most people get sold the wrong kW

 

This is where most boiler quotes go wrong, and it's the single most common reason a five-year-old boiler dies a year later than it should.

 

Boiler "size" means kilowatt output, not physical dimensions. Two outputs matter:

  • CH output: kilowatts going to your central heating (the radiators).

  • DHW output: kilowatts available for hot water at the tap.


A combi has one figure that does both. A system or regular boiler has CH only, with the cylinder doing the hot-water work.
These are starting points, not gospel. The right answer comes from a heat-loss calculation.

These are starting points, not gospel. The right answer comes from a heat-loss calculation.

Don't trust a tree on a website. The last 20% of this decision needs eyes on. We do free home surveys with no commitment to buy. Book one at ddwilson.com/quick-quote.

Why bedroom count is a lazy proxy


Two three-bed semis on the same Liverpool street can have wildly different heat losses. One has solid walls, single-glazed windows and a draughty loft hatch. The other had cavity insulation, double glazing and loft insulation done in 2019. The first needs maybe 28 kW of CH output; the second needs 14 kW.
 

Quote a 30 kW combi into both, which is what a high-volume installer often does, and the second house has a boiler that short-cycles: it fires up, hits its target temperature in three minutes, shuts off, and repeats every few minutes for the entire winter. That's the boiler equivalent of starting a car engine, switching it off, then starting it again, all day, every day. The boiler ages prematurely. It will fail at year four instead of year fourteen.
 

A proper installer does a heat-loss calculation, sometimes called a room-by-room heat-loss survey. It takes us about an hour. It's free with our quote.
 

For more on sizing in plain English, our post on how to choose the right gas boiler for your home walks through it with worked examples.​

What 'fully fitted' should include (and what cheap quotes leave out)

Two quotes on a Liverpool kitchen table can be £400 apart and look identical on the front page. The difference is almost always in what's bundled.


What every "fully fitted" quote should include

  • The boiler itself, brand new, sealed, with manufacturer warranty registered to the address

  • A magnetic system filter (Adey, Spirotech or Fernox) fitted on the return

  • A scale reducer or inhibitor on the cold mains feed (if your area has hard water, and ours does in much of South Lancashire and the Wirral)

  • A power flush or chemical clean of the existing system, before the new boiler goes on

  • New flue and flue terminal to current building regulations

  • A wireless room thermostat, programmable, with at least seven-day scheduling

  • New isolation valves on the gas, hot and cold supplies

  • Boiler controls and external pipework, lagged

  • Commissioning, including full flue-gas analysis, with a Benchmark certificate signed and given to you

  • Manufacturer warranty registration completed by us, on the day, in front of you

  • A two-year workmanship guarantee from us, in writing

  • Removal and responsible disposal of your old boiler

trench for new water supplies

What cheap quotes often leave out

  • The magnetic filter (saves them about £80, voids manufacturer warranty cover for sludge-related faults)

  • The system flush

  • The scale reducer

  • New flue components (they reuse your old one)

  • The thermostat (you're handed a quote for the boiler only)

  • The Benchmark certificate

  • Late warranty registration, sometimes weeks after install (your warranty clock can start late, or not at all)


The single line that catches most cheap quotes: skipping the magnetic filter saves £80 and voids £2,000-plus of warranty cover. The manufacturers (Vaillant, ATAG, Worcester, Ideal, Alpha) have all written sludge-related fault clauses into their guarantees. A filter is no longer optional. The cheap quote is selling you a warranty you can't claim on.

For the full parts checklist you can print and bring to every quote, see the full installation parts checklist.

Honest pricing, £600 to £4,000-plus

All prices below are inclusive of VAT, fully fitted to the parts list above, valid as of May 2026. We review them every spring.


Band A: labour-only swap (you supply the boiler)

From £600. You bought a boiler online or had one supplied by your landlord. We swap it in, commission it, and register the warranty. No supply, no parts list above. We'll be honest: we don't push this option, because we can't warrant a boiler we didn't supply, and we can't get the manufacturer to come out under warranty if the install paperwork doesn't tally. We'll do it if you want. We'll explain the trade-off.


Band B: entry-level combi, simple swap

From £1,599. Like-for-like swap, modest-sized house, boiler stays in the same place, gas and flue stay where they are. Mid-tier brand, manufacturer warranty included.


Band C: most-chosen Vaillant install

From £2,599. A Vaillant ecoTEC Plus combi, properly sized, with a 10-year manufacturer warranty backed by our Vaillant Advance Master Tech accreditation. Fully fitted to the parts list above. This is the sweet spot for the majority of Liverpool semis.


Band D: ATAG iC Economiser, with up to 14-year warranty

From £2,799. ATAG iC combi, 10-year warranty as standard, extending up to 14 years through our Selected Partner programme. The longest warranty cover available in the domestic market without bolt-on third-party policies.


Band E: system boiler with new Megaflo cylinder

From £3,499. Vaillant or ATAG system boiler, new unvented cylinder, removal of old gravity-fed setup, conversion to mains pressure. Three-bedroom-plus, two-bathroom houses. Significant work, takes two to three days.


What pushes the price up

  • Boiler relocation (kitchen to garage, ground floor to loft): £400 to £900

  • Gas-pipe re-route or upsize (often needed when going from a 24 kW to a 35 kW): £250-plus

  • Scaffold for high-level flue terminals: £180-plus

  • Combi-to-system conversion or vice versa: £600 to £1,200

  • New unvented cylinder (Megaflo or similar): £900-plus

  • Power flush of a heavily sludged system: £450-plus

For the full pricing breakdown with worked examples, see our post on how much it costs to install a new boiler and our current best boiler deals.

Warranties decoded: Vaillant, ATAG and Alpha

A long warranty is only as good as the install behind it. Three of the strongest warranties on the UK market come with conditions.

Vaillant: 10 years through the Advance Master Tech installer scheme. We hold that accreditation, which is why our Vaillant installs come with the 10-year cover registered in your name on the day. Conditions: annual service from year two onwards, magnetic filter fitted at install, manufacturer registration within 30 days, original installer-supplied parts only. Our Vaillant install guide covers the detail.
 

ATAG: up to 14 years through the Selected Partner scheme on the iC Economiser range. 10 years is standard. The further four years come through our partner status. Conditions: identical to Vaillant on the magnetic filter, annual service and registration. ATAG warranties are transferable on house sale within the warranty period, which Vaillant is not. See our ATAG boilers page for the current models.


Alpha: 5 to 10 years depending on the model and installer accreditation. The E-Tec Plus range, fitted by an approved installer, currently carries 10 years.


The three conditions all three warranties share

  1. Annual service, by a Gas Safe registered engineer, every 12 months from year two onwards. Miss one and the manufacturer can lawfully decline a future claim.

  2. Magnetic filter fitted at install and serviced annually. Skip it and any sludge-related fault is on you.

  3. Manufacturer registration completed within 30 days of install. If your installer says they'll register "later", get it in writing, then check it on the manufacturer's portal yourself a fortnight later.

A 10-year warranty is not 10 years of free repairs. It is 10 years of warranted parts replacement on the boiler, on the conditions above. If you don't service it, don't fit a filter, or don't register it, the warranty becomes a piece of paper.
 

Finance, in plain English (0% APR over 12 months)

We offer 0% APR finance on most installs, repayable over 12 months. Longer terms (24 to 60 months) are available with interest.


Representative example

Cash price £2,599. Deposit £0. 12 monthly payments of £216.58. Total repayable £2,599. 0% APR.


How it works

You apply through our finance partner, Switcha Limited. The application is a soft search first, which doesn't affect your credit score until you accept. Most decisions come back the same day. If you're approved and you accept, the install goes ahead as planned, and you start the monthly payments after the boiler is on.


What's required

  • UK resident, 18 or over

  • A regular income

  • A bank account that can take Direct Debits


We don't see your full credit file. The lender does. We get a yes/no/refer back.

FCA disclosure: DD Wilson Gas And Heating Engineers Ltd (FCA Reference 1017595) is an Introducer Appointed Representative of Switcha Limited, which is authorised and regulated by the Financial Conduct Authority. Switcha Limited acts as a credit broker, not a lender, and offers credit facilities from a panel of lenders. Credit is subject to status and affordability assessment.


For the live application form and terms, see finance options.

​Eight red flags from rogue installers

Every winter, we get the same calls. Half-installed system. Voided warranty. Deposit gone. The eight signs below are the ones we see every year.

1. "Cash discount today only"

A genuine boiler quote is good for at least seven days, usually 30. Pressure to sign on the day is a sales technique, not an offer.


2. No Gas Safe ID card

A Gas Safe registered engineer carries an ID card. The card has their name, photo, registration number, expiry date and a list of categories they're qualified for. If you ask and they can't show one, or the card has expired, do not let them on the gas. Verify any registration at gassaferegister.co.uk.


3. Verbal-only quote

If it's not in writing, it doesn't exist. A real quote lists the boiler model, the parts above, the price, the VAT treatment, the timeline and the warranty terms. A scribble on the back of an envelope is not a quote.


4. "You don't need a magnetic filter"

You do. The manufacturers say so. The cheap installer doesn't want to fit one because it costs them parts and time. Walk away.


5. "We'll register the warranty later"

Manufacturer warranty registration is a 10-minute job at the end of the install. If they don't do it on the day, in front of you, with the registration confirmation emailed to you, they aren't going to do it.


6. Headline price ex-VAT

The headline price on a domestic boiler quote should always be VAT-inclusive. If you have to read the small print to find the VAT, the company is being sneaky.


7. Cash up-front, full amount

A reasonable deposit (often 10 to 20% on supply orders) is fine. Full payment in cash before the boiler goes on the wall is not. A real installer takes a deposit, schedules the work, and bills the balance on completion.


8. No verifiable company

Companies House is free to search. A real UK installer has a registered company number, an address that isn't a residential maisonette, and accounts filed. We're number 14258693.
​

For the printable one-page version of these red flags, see our trustworthy boiler installation services article.

The DDWilson install, day by day


A typical Vaillant or ATAG combi install with us looks like this.


Day 0: Free home survey (about an hour). One of our engineers comes round, measures up, runs a heat-loss calculation, talks through your options, leaves you with a written quote. No pressure. No "today only" prices.


Day 1, morning (8:30 start). Two engineers on site. Old boiler off, isolated, drained. Pipework prepped. Power flush kicks off in parallel. We lay dust sheets on every floor we walk over.


Day 1, afternoon. New boiler hung. Flue cut and sealed. Magnetic filter fitted on the return. Scale reducer (if applicable). Gas pipe upgraded if the new output requires it. Thermostat paired and tested.


Day 1, end of day. Commissioning. Full flue-gas analysis with a calibrated analyser. Benchmark certificate filled in, signed, and handed to you. Manufacturer warranty registered on our laptop, in front of you, with the confirmation email sent to your inbox before we leave.


Day 2 onwards. You've got a two-year workmanship guarantee from us, on top of the manufacturer warranty on the boiler. If anything moves, drips or whistles in those two years, we come and sort it.


For a real installation case study from a customer in the area, see our Vaillant install review.


Aftercare and servicing: what a real annual service includes

A 15-minute "service" is not a service. A real annual service takes 60 to 75 minutes and follows a 10-point checklist.

  1. Visual inspection of the boiler, pipework, flue and ventilation

  2. Removal of the case, internal inspection for corrosion or leaks

  3. Combustion analysis using a calibrated flue-gas analyser

  4. Burner inspection and clean

  5. Heat exchanger inspection, with descale or clean if needed

  6. Condensate trap clean

  7. Magnetic filter clean (and inhibitor top-up if levels are low)

  8. Pressure check, expansion vessel re-charge if needed

  9. Safety device function checks (PRV, low-water cut-off, flame-supervision device)

  10. Service report issued, signed, dated, and emailed to you

If yours took 15 minutes, it wasn't a service.

We offer service plans from £12 a month, which include the annual service, priority booking, and discounted call-outs. See our service package deals and boiler services for the full options.
 

Real customer stories

"Excellent service from start to finish. Free quote arrived in two days, no pressure. Vaillant ecoTEC Plus fitted in a single day, the lads cleaned up after themselves, and the warranty was registered before they left. Recommended."


Sandra W., Liverpool. Vaillant install, February 2025.
 

"We had three quotes for a combi-to-system conversion. DD Wilson's wasn't the cheapest but it was the most thorough. They explained why we needed a Megaflo, did the heat-loss calculation properly, and finished on time. Two months in and the difference upstairs is night and day."


Paul N., Liverpool. full boiler system install, January 2026.


For more verified reviews, see our testimonials page.
 

Meet the Wilsons

DD Wilson Gas And Heating Engineers Ltd was started in 1998 by Darren Wilson out of a Bootle van. We're named after our two sons, Darren and Dylan. Hence the two Ds.

Twenty-eight years on, we run 12 staff out of Unit 8, Redwood Point, Woodward Road, L33 7UZ, including three apprentices we trained from college. We've fitted thousands of boilers across Merseyside, the Wirral, Cheshire and into South Lancashire and North Wales, and we sponsor Carla Lane Animal Rescue in Melling, which matters to us.

The reason people ring us, and the reason 2,365-plus people have left a review averaging 4.9 stars, is that we treat every house like it's our mum's. That's not marketing copy, it's the actual brief. If we wouldn't fit it in our mum's kitchen, we don't fit it in yours.

Read more about our journey from a single van to 28 years of installs.

Where we work

Same-day service to Hoylake in the west, Chester in the south, St Helens in the east, and Crosby in the north. We've fitted boilers in Wrexham and Southport this month alone.

Domestic service radius: 35 miles from our Liverpool depot. Commercial: 100 miles.

​

For the full list of postcodes, see the local areas we cover. Specific area pages: Southport, Chester, St Helens, Aughton, Ormskirk, Cheshire and Runcorn.
 

Outside the ring? Ring us anyway. 0151 739 8945.​


Office: 0151 739 8945


Email: info@ddwilson.com


Online quick quote: ddwilson.com/quick-quote


Book a call-out online: ddwilson.com/book-online


We're Gas Safe 583586, FCA 1017595, Companies House 14258693, Vaillant Advance Master Tech, ATAG approved installer, 4.9 stars across 2,365-plus verified reviews.


You only care how much we know, when you know how much we care.


Ring us when you're ready. We'll be on the tools either way.


Darren Wilson, on behalf of all of us at DD Wilson

Frequently asked questions

Boiler Buying Guide With Check List

Here is the digital guide for you to download and keep for reference when you need it most.

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