Unvented Cylinder Replacement Cost London 2026
What replacing an unvented hot water cylinder costs in London in 2026: fixed labour prices, why the cylinder is quoted separately, what a conversion adds and what moves the price.
Replacing an unvented cylinder in London costs £1,450 for our labour and miscellaneous parts, plus the cylinder, which is quoted as its own line. A new installation or vented-to-unvented conversion is £2,400 plus the cylinder. We do not currently charge VAT. Published UK guides put the all-in total at roughly £2,000 to £3,800.
Replacing an unvented hot water cylinder in London costs £1,450 for our labour and miscellaneous parts, plus the cylinder. A first-time installation or a vented-to-unvented conversion is £2,400 plus the cylinder. These are the prices we quote, checked on 27 October 2026, and we do not currently charge VAT. The cylinder is always a separate line on the written quote.
Get a fixed price for your cylinder in a couple of minutes, or read on for what the number depends on and how to check any quote you receive.
Our Fixed Prices
- Cylinder replacement, labour and miscellaneous parts: £1,450. A like-for-like swap: drain down, remove the old cylinder, fit the new one, reconnect and commission. The cylinder is a separate line.
- New cylinder installation: £2,400. Pipework, installation, commissioning and Building Regulations work for a first-time installation or a vented-to-unvented conversion. The cylinder is a separate line.
- Diagnosis: £180. An engineer tests the cylinder, its controls and safety devices and gives you a written repair-or-replace recommendation with a fixed price for each.
- Annual unvented service: £180. The yearly checks manufacturers ask for to keep a tank warranty valid.
Pre-booked cylinder work has no call-out fee. Same-day and out-of-hours emergency call-outs are £60 at any hour. Parking and congestion charge, where they apply, are shown as separate lines.
Why The Cylinder Is A Separate Line
The make, size and type of cylinder move the total more than any other single item. A 150-litre direct cylinder and a 300-litre smart cylinder are very different purchases, and a quote that blends them into one figure hides what you are paying for each. Splitting the cylinder out means you can put two quotes side by side and see whether a lower total is a cheaper cylinder, less work, or something left out.
Your written quote should name the make, model and litres of the cylinder, and show labour, the cylinder and any extras on separate lines. If it does not, ask for it.
What published guides say
Published ranges are wide because they mix job types. Hamuch's London estimate pages put a like-for-like unvented replacement at about £2,245 to £2,369, excluding VAT and call-out. BookaBuilderUK gives £2,000 to £3,800 for the UK, with London at the top of that range. People posting on forums report quotes from about £1,600 to £7,000 for similar-sounding jobs, but those are anecdotes, not prices, and the jobs behind them are rarely the same. These are not our prices, and they bundle the cylinder, labour and extras differently, which is the reason we show ours split out.
What Moves The Price
- Vented to unvented. A conversion adds a new mains feed, a discharge route to the outside, an expansion vessel and removal of the loft tank. That is the £2,400 job, not the £1,450 one.
- The discharge pipe route. Approved Document G sets out how the tundish and discharge pipe must be arranged. In a mid-floor flat with no nearby outside wall, this can cost more time than the swap itself, and sometimes decides whether unvented is possible.
- Access. Loft hatches, tight airing cupboards and top-floor flats with no lift change how long carrying and fitting takes.
- Which cylinder. Size, brand, direct or indirect, and whether it is a smart cylinder. This is its own line on the quote.
- Old pipework. Corroded valves or isolators that will not shut off are found at survey and cost extra to replace.
- Mains pressure and flow. If the supply is too weak for an unvented cylinder, a vented swap or other fix may be the honest answer.
Vented To Unvented Conversion
If your cylinder is fed from a loft tank, moving to unvented gives mains-pressure showers and frees the loft, but it is a bigger job than a like-for-like swap. Our price for a first-time installation or conversion is £2,400 plus the cylinder, covering pipework, installation, commissioning and Building Regulations work.
Before choosing unvented, check the mains. The water supplier's guaranteed standard is low, about 0.7 bar, with about 1 bar as its aim. Heatrae Sadia's Megaflo Eco installation manual asks for at least 1.5 bar and 20 litres a minute at the cylinder. Measure dynamic pressure with water running and time a bucket fill rather than trusting a static gauge. If the supply falls short, a vented swap is usually the better recommendation.
How To Compare Quotes
These questions work on ours and on anyone else's:
- Is the cylinder a separate line, with make, model and litres written down?
- Does the price include removing and disposing of the old cylinder?
- Where will the tundish and discharge pipe run, and has anyone checked it reaches outside?
- Is the installer G3 qualified, and who notifies Building Control?
- Will I get the Building Regulations certificate, and when?
- Is mains pressure and flow being measured, or assumed?
- What happens if old isolators or valves will not shut off?
- Who do I call if it drips or fails in the first year?
G3, Building Regulations And Warranty
An unvented cylinder over 15 litres is covered by Part G of the Building Regulations (Approved Document G). Installing or modifying one is notifiable work, so the installer must be G3 qualified and either belong to a competent person scheme or notify Building Control. Ask for the certificate afterwards and keep it with your insurance and conveyancing papers. Our G3 explainer covers the detail.
Tank warranties differ by maker and all depend on registering the cylinder on time and servicing it each year. Heatrae Sadia's current Megaflo Eco wording is lifetime for the first domestic owner and 30 years on resale, with registration required within 30 days. Telford is lifetime with registration within 28 days. Joule is 25 years on the vessel with registration within 28 days. Scale damage is usually excluded, and in hard-water London that matters. Check the current terms for the exact model you are quoted. Our workmanship is guaranteed for 12 months on top.
Ongoing Costs
After installation, running costs are small but recurring:
- Annual service: £180.
- Expansion vessel replacement: typically £180 to £280 fitted.
- Temperature and pressure valve: typically £120 to £160 fitted.
- Immersion element: typically £90 to £130 fitted.
These part prices are typical figures from our earlier work and are confirmed in writing before any repair. They are a fraction of a new cylinder, which is why a £180 diagnosis is worth doing before you decide to replace. See the repair-or-replace guide for which faults usually mean a new tank.
Need a fixed price? Request one online, call 0207 046 1363 or WhatsApp 07456 975436 with your postcode and what has gone wrong.
FAQs
The answers are in the FAQ schema for this page. In short: £1,450 plus the cylinder to replace, £2,400 plus the cylinder to convert or install new, £180 to diagnose or service, no VAT. For the wider service, see our hot water cylinder replacement hub and the unvented cylinders page.
Key Takeaways
- Our fixed prices: £1,450 labour and parts to replace a cylinder, £2,400 for a new installation or conversion, £180 diagnosis, £180 annual service. No VAT is charged.
- The cylinder is a separate line on every quote, with make, model and litres written down, so you can compare quotes like for like.
- Published UK guides put the all-in total at roughly £2,000 to £3,800. Forum posts show wider ranges, but those are anecdotes, not prices.
- Access, the discharge pipe route and whether you are converting from vented decide the price more than the brand does.
- Check mains pressure and flow before you choose unvented. One manufacturer asks for 1.5 bar and 20 litres a minute, above the water supplier's guaranteed standard.
- Many cylinder faults are a valve, expansion vessel, thermostat or element. A £180 diagnosis tells you whether you need a new tank at all.
