Hot Water Cylinder Replacement Cost UK 2026
How much does it really cost to replace a hot water cylinder in 2026? From straightforward vented swaps to full unvented upgrades and heat pump cylinders, here are the honest prices from a G3-certified installer covering Andover, Marlborough & Hungerford.
If your hot water cylinder is leaking, producing rusty water, or simply past its best, you’re probably wondering how much a replacement will cost. The answer depends on several factors: the type of cylinder you choose, whether you’re doing a like-for-like swap or upgrading to a different system, and the complexity of your existing pipework.
As a G3-certified plumber installing and replacing hot water cylinders across Andover (SP10/SP11), Marlborough (SN8), and Hungerford (RG17), I’ve put together this guide based on actual jobs I’ve completed. These are real-world prices, not estimates pulled from generic cost databases.
What This Guide Covers
- - Complete cost breakdown by cylinder type
- - Vented vs unvented comparison
- - Labour costs and what affects them
- - Heat pump cylinder pricing
- - Signs your cylinder needs replacing
- - G3 certification requirements
- - What to expect from a professional install
- - Local factors affecting price
Hot Water Cylinder Replacement Costs at a Glance
Rosebourne's figures, from the same model as the calculator on the unvented page: cylinder, fittings and sundries, plus the labour. The range in each cell runs from a 150 L to a 300 L cylinder. Everything excludes VAT and is fixed in writing after a free survey.
| Cylinder Type | Cylinder, fittings and sundries | Labour | Total Installed |
|---|---|---|---|
Vented (Gravity-Fed) Cylinder Like-for-like replacement | Cheaper than unvented; quoted on survey | £700 | Labour plus the cylinder you choose |
Unvented (Mains-Pressure) Cylinder New install or replacement | £940 to £1,450 | £700 | £1,640 to £2,150 |
Vented to Unvented Upgrade System conversion required | £940 to £1,450 | £1,450 (two days) | £2,390 to £2,900 |
Heat Pump Cylinder For ASHP/GSHP systems | Quoted after survey | Quoted after survey | Quoted after survey |
Thermal Store Cylinder Multi-fuel / renewable compatible | Quoted after survey | Quoted after survey | Quoted after survey |
All prices exclude VAT. The model assumes straightforward access; long pipe runs, asbestos removal or structural work are found on the survey and priced then. Heat-pump and thermal-store cylinders vary too much in size and coil to carry a from-price.
Rosebourne Plumbing Pricing
Our minimum charge is £150 + VAT for any plumbing work. A like-for-like unvented cylinder, supplied and fitted, starts from £1,640 + VAT; labour alone is £700 + VAT for the day. We provide fixed-price quotes before any work begins.
Vented vs Unvented Cylinders: Which Do You Have and Which Should You Choose?
Understanding the difference between vented and unvented systems is the first step in working out what your replacement will cost. Each has distinct advantages, installation requirements, and price points.
Vented Cylinder
A vented cylinder is fed by a cold water storage tank, usually in the loft. Water pressure depends on the height difference between the tank and the taps. This is the traditional system found in most UK homes built before 2000.
Advantages
- +Lower cost: a cheaper cylinder on the same day of labour
- +Any competent plumber can install (no G3 needed)
- +Simpler system with fewer components to fail
- +Works regardless of mains water pressure
- +Water reserve in tank during mains supply interruption
Disadvantages
- -Lower water pressure at taps (gravity-dependent)
- -Requires loft space for cold water tank
- -Cold water tank can freeze in harsh winters
- -May need a shower pump for decent shower pressure
Unvented Cylinder
An unvented cylinder connects directly to the mains water supply, delivering hot water at mains pressure to every tap and shower in your home. These systems have become the standard in new-build properties across the UK.
Advantages
- +Mains-pressure hot water to all outlets
- +No loft tank needed, freeing up space
- +Better shower performance without a pump
- +No risk of contamination from open tank
- +Adds value to your property
Disadvantages
- -Higher cost (£1,640 to £2,150 + VAT like-for-like; more to convert)
- -Requires G3-qualified installer (legal requirement)
- -Needs adequate mains pressure (min 1.5 bar)
- -Annual service recommended for safety valves
Which System Is Right for Your Property?
Stick with Vented If...
- - Budget is tight
- - Mains pressure is low (below 1.5 bar)
- - Your existing system works well enough
- - You only need basic hot water performance
Upgrade to Unvented If...
- - You want better shower pressure
- - You have 2+ bathrooms
- - Mains pressure is good (1.5+ bar)
- - You’re renovating anyway
Choose Heat Pump Cylinder If...
- - You have or plan a heat pump
- - You want to future-proof your home
- - You’re targeting an EPC upgrade
- - Budget allows for a survey-quoted install
What Affects Hot Water Cylinder Replacement Cost?
Two seemingly identical cylinder replacements can vary by hundreds of pounds. Here are the real factors that determine what you’ll pay.
Cylinder Type & Size
A vented cylinder is the cheaper unit. Unvented, supplied and fitted by Rosebourne, starts at £1,640 + VAT for 150 L and £2,150 + VAT for 300 L; the cylinder itself is £940 to £1,450 + VAT of that. Heat pump cylinders with larger coil surface areas command a further premium.
Manufacturer & Brand
Budget brands (RM Cylinders, Gledhill) start lower but may have shorter warranties. Mid-range (Megaflo, Heatrae Sadia) offer good value. Premium brands (Worcester Bosch, Vaillant, Joule) cost more but often come with longer warranties and better build quality.
Accessibility & Location
A cylinder in a ground-floor cupboard with good access is straightforward. One in a tight loft space, or requiring removal down narrow stairs, adds time and labour cost. Some older properties in Marlborough and Hungerford have particularly challenging access.
Pipework Modifications
A like-for-like swap with compatible connections is the cheapest option. If pipe sizes differ, routes need changing, or you’re upgrading from vented to unvented, the extras are priced as lines: upgrading the incoming mains to the cylinder is £350 + VAT and taking the old loft tank out is £250 + VAT.
Additional Components
Unvented installations require safety components: expansion vessel, temperature & pressure relief valve, pressure reducing valve and tundish. They are legally required, and they sit inside the cylinder, fittings and sundries figure above rather than appearing as surprises on the bill.
Old Cylinder Disposal
Removing and disposing of the old cylinder is usually included in a professional quote. However, very old cylinders with asbestos insulation (common in pre-1980 homes) require specialist removal by a licensed contractor, quoted separately.
Labour Cost Breakdown: What You’re Actually Paying For
Vented Cylinder Swap (£700 + VAT labour, one day)
- - Draining down existing cylinder (30-60 min)
- - Disconnecting and removing old unit
- - Positioning and connecting new cylinder
- - Refilling, bleeding, and testing
- - Checking immersion heater and thermostat
- - Disposing of old cylinder
Typical duration: 3-5 hours
Unvented Cylinder Install (£700 + VAT like-for-like, £1,450 + VAT to convert)
- - All tasks above, plus:
- - Installing expansion vessel
- - Fitting pressure reducing valve
- - Installing T&P relief valve with tundish
- - Building Control notification
- - Commissioning and safety testing
- - Removing loft tank (if upgrading from vented)
Typical duration: 1-2 days
G3 Certification: Why It Matters for Unvented Cylinders
If you’re considering an unvented cylinder, understanding the G3 qualification requirement could save you from an illegal installation, invalidated insurance, and serious safety risks.
What Is G3 Certification?
G3 refers to Part G3 of the Building Regulations, which governs the installation of unvented hot water storage systems over 15 litres. Any engineer installing, commissioning, or servicing an unvented cylinder must hold a current G3 qualification.
The qualification covers the safe installation and maintenance of pressurised hot water systems, including understanding thermal expansion, pressure relief, and the multiple safety devices required on every unvented system.
Warning: Illegal Installations
Having an unvented cylinder installed by someone without G3 certification is a Building Regulations offence. It also invalidates your home insurance and could be dangerous. An improperly installed unvented system can produce steam explosions if safety devices are incorrectly fitted.
What G3 Installation Includes
- 1Pre-installation checks - Mains pressure test, flow rate measurement, and assessment of existing pipework capacity.
- 2Safety device installation - Temperature and pressure relief valve, expansion vessel correctly sized for the cylinder, pressure reducing valve, and tundish with visible discharge pipework.
- 3Commissioning - Testing all safety valves, verifying correct operation under normal and fault conditions, and setting thermostat temperatures.
- 4Building Control notification - Formal notification to your local authority that the installation complies with Part G3 of the Building Regulations.
- 5Documentation - Benchmark commissioning checklist, manufacturer warranty registration, and compliance certificate for your records.
Heat Pump Cylinders: Costs & Considerations
With the Boiler Upgrade Scheme offering £7,500 towards heat pump installations, more homeowners across Andover, Marlborough, and Hungerford are making the switch. A heat pump cylinder is an essential part of this system.
Why Heat Pump Cylinders Cost More
Heat pumps operate at lower temperatures than traditional boilers (typically 45-55 degrees C versus 65-80 degrees C for a gas boiler). To compensate, heat pump cylinders need a larger internal coil surface area to extract sufficient heat from the lower-temperature water. They’re also typically larger in capacity (200-300 litres vs 120-180 litres for conventional systems) and have superior insulation to retain heat longer.
Planning ahead? If you’re replacing a cylinder now but considering a heat pump in the next few years, it may be worth investing in a heat pump-compatible cylinder from the start. This avoids paying for two cylinder replacements. Read our detailed guide on heat pump cylinder installation or learn more about our heating services.
7 Signs Your Hot Water Cylinder Needs Replacing
Not sure whether you need a replacement or just a repair? Here are the warning signs that indicate your cylinder is reaching the end of its life.
Visible Leaking
Water pooling around the base of your cylinder is the clearest sign of failure. Small weeps can become major leaks quickly. If the cylinder body itself is leaking (not just a valve), replacement is the only option.
Rusty or Discoloured Water
Brown or orange-tinged hot water indicates internal corrosion. This is common in cylinders over 15 years old, particularly in hard water areas like parts of Andover and Hungerford where limescale accelerates deterioration.
Inconsistent Temperatures
If your hot water temperature fluctuates or the water doesn’t get as hot as it used to, the thermostat or immersion element may be failing. While these can sometimes be replaced individually, in an old cylinder it often signals wider problems.
Excessive Heating Time
A cylinder that takes significantly longer to heat up than it used to has likely built up internal limescale, reducing heat transfer efficiency. This also increases your energy bills. In severe cases, the coil becomes so scaled that replacement is the only practical solution.
Strange Noises
Banging, popping, or rumbling sounds during heating cycles often indicate limescale build-up on the immersion heater or internal coil. While descaling is possible on some cylinders, the noise usually means the problem is advanced.
External Corrosion
Rust patches on the outer casing suggest moisture has been present for some time. While surface rust on fittings is normal, corrosion on the cylinder body itself means the structural integrity is compromised and replacement should be planned promptly.
Age: Over 15-20 Years Old
Even if your cylinder isn’t showing obvious signs of failure, cylinders over 15-20 years old are operating on borrowed time. Modern cylinders are significantly more energy-efficient, better insulated, and designed to work with contemporary heating systems. Proactive replacement before a failure occurs avoids the emergency premium and lets you plan the work at a convenient time. Many properties across Andover still have original cylinders from the 1990s or earlier that are well overdue for replacement.
What Size Cylinder Do You Need?
Choosing the right size cylinder affects both the upfront cost and your daily hot water experience. Too small and you’ll run out of hot water; too large and you’re heating water you don’t use.
| Household Size | Bathrooms | Recommended Size | Cylinder, fittings and sundries (+ VAT) |
|---|---|---|---|
| 1-2 people | 1 | 90-120 litres | £940 (150 L is the smallest we price) |
| 2-3 people | 1-2 | 120-170 litres | £940 to £1,020 |
| 3-4 people | 2 | 170-210 litres | £1,020 to £1,150 |
| 4-5 people | 2-3 | 210-300 litres | £1,150 to £1,450 |
| 5+ people | 3+ | 300+ litres | £1,450; larger quoted after survey |
These are general guidelines. Actual sizing depends on usage patterns, number of showers vs baths, and whether you have a dishwasher and washing machine using hot water. We always assess your specific needs before recommending a size.
What to Expect from a Professional Cylinder Replacement
Whether you’re in Andover, Marlborough, Hungerford, or the surrounding villages, here’s exactly what happens when Rosebourne Plumbing replaces your hot water cylinder.
Survey & Quote
I visit your property to assess the existing cylinder, check access, measure mains pressure (for unvented systems), and discuss your hot water needs. You receive a written fixed-price quote with no hidden extras. This survey is free of charge.
Scheduling & Preparation
Once you accept the quote, we schedule the work at a time that suits you. I order the cylinder and all required components. For unvented installations, I handle the Building Control notification. You’ll need to plan for being without hot water during the installation.
Installation Day
The old cylinder is drained down and safely removed. The new cylinder is positioned, connected to your heating and water systems, and all safety devices are fitted (for unvented). The system is filled, bled, and thoroughly tested. I clean up all work areas and take the old cylinder away for recycling.
Handover & Documentation
I walk you through the new system, show you the controls, and explain how to get the best from your new cylinder. You receive all documentation including the manufacturer’s warranty, benchmark commissioning record, and (for unvented systems) the Building Regulations compliance certificate. All work comes with our 12-month workmanship guarantee.
Worked Examples from the Cylinder Calculator
These are illustrations from the same model as the calculator on our unvented page, not records of particular jobs. Every job is different; the free survey turns the model into one fixed price.
150 L like-for-like unvented
One bathroom, one or two people. The existing unvented cylinder swapped in the same position, mains already in place, old unit taken away.
210 L like-for-like unvented
One to two bathrooms, three or four people. Same position and the same day of labour, a bigger cylinder.
210 L conversion from a vented system
Tank in the loft out, new mains-pressure supply, discharge pipework and expansion vessel in. Shown with the loft tank removed and the incoming mains upgraded.
The one real figure behind this page: a 150 L unvented cylinder supplied and fitted in Great Bedwyn in September 2025 came to £1,651 + VAT (£1,981 inc VAT). The model is anchored on it.
Frequently Asked Questions: Hot Water Cylinder Replacement Costs
Answers to the most common questions homeowners in Andover, Marlborough, and Hungerford ask about cylinder replacement pricing and installation.
How much does it cost to replace a hot water cylinder in 2026?
A like-for-like unvented replacement, supplied and fitted by Rosebourne, runs from £1,640 + VAT for a 150 L cylinder to £2,150 + VAT for 300 L; £700 + VAT of that is the day's labour. Converting from a vented, tank-in-the-loft system is £2,390 to £2,900 + VAT, because it is two days (£1,450 + VAT) plus the new mains supply, discharge pipework and expansion vessel. A vented like-for-like swap uses the same day of labour with a cheaper cylinder, and heat-pump cylinders are quoted after a survey. Every figure excludes VAT and comes from the same model as the calculator on our unvented page; the fixed price is confirmed in writing after a free survey.
Do I need a G3-qualified engineer to install an unvented cylinder?
Yes, by law in England and Wales, unvented hot water cylinders over 15 litres must be installed by a G3-qualified engineer. This is a Building Regulations requirement (Part G3). The installer must notify Building Control upon completion. Installing without G3 certification is illegal and invalidates your insurance. Will Gaze at Rosebourne Plumbing holds current G3 certification for unvented cylinder installations across Andover, Marlborough and Hungerford.
Is it worth upgrading from a vented to an unvented cylinder?
Upgrading from vented to unvented is worth it if you want mains-pressure hot water throughout your home, better shower performance without a pump, and to free up loft space by removing the cold water storage tank. The conversion is £2,390 to £2,900 + VAT depending on cylinder size, and what you get is mains-pressure hot water at every outlet at once. However, your mains water pressure must be at least 1.5 bar for an unvented system to work properly.
How long does a hot water cylinder replacement take?
A like-for-like vented cylinder replacement typically takes 3-5 hours. Replacing a vented cylinder with an unvented system takes 1-2 days because additional pipework, safety valves, and an expansion vessel need installing. Heat pump cylinder installations usually take 1-2 days. At Rosebourne Plumbing, we always provide a realistic timeframe before starting work.
What are the signs that my hot water cylinder needs replacing?
The main signs your cylinder needs replacing include: rusty or discoloured hot water, visible corrosion or rust on the cylinder body, water pooling around the base, inconsistent water temperatures, the cylinder taking much longer to heat up, unusual noises during heating, and the cylinder being over 15-20 years old. If you notice any leaking from the cylinder itself, replacement is usually necessary rather than repair.
Can I get a hot water cylinder replaced the same day in Andover or Marlborough?
Same-day like-for-like vented cylinder replacements are sometimes possible if we have the right cylinder in stock or can source it quickly. For planned replacements, we typically schedule within 3-5 working days across Andover (SP10/SP11), Marlborough (SN8), and Hungerford (RG17). Unvented installations always require advance planning due to the Building Control notification requirement. Call 01264 502027 to discuss your timescale.
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