The Complete UK Hot Water Cylinder Guide 2025
Expert advice from Hampshire's G3-certified installers | 25 years experience | Free quotes
Choosing the right hot water cylinder can save you thousands in energy bills and prevent years of frustration. Whether you're replacing a failed cylinder, upgrading to mains pressure, or installing a heat pump system, this comprehensive guide covers everything you need to know.
Find Your Perfect Cylinder in 3 Questions
Quick decision guide to help you choose the right hot water cylinder
What's your situation?
What heating system?
What's your priority?
Hot Water Cylinder Basics: What You Need to Know
Understanding the four main types of hot water cylinders
Vented Direct
Electric immersion heater only. Fed from header tank in loft. Low pressure (0.5-1.5 bar). Cheapest option but poorest performance.
£700-1,100 installed
Best for: Budget installations
Vented Indirect
Heated by boiler via coil. Fed from header tank. Low pressure. Traditional system still common in older homes.
£1,200-1,800 installed
Best for: Older properties
Unvented Direct
Electric immersion heater. Mains pressure (2-4 bar). No header tank. Powerful showers. Requires G3 certified installer.
£1,600-2,400 installed
Best for: Off-gas properties
Unvented Indirect
Heated by boiler or heat pump. Mains pressure. Most common modern installation. Best performance.
£1,800-3,500 installed
Best for: Modern homes
Building Regulations G3 Requirement
CRITICAL: Unvented cylinders must comply with Building Regulations Part G3 (England & Wales), Technical Standard P3 (Scotland), or Building Regulation P5 (Northern Ireland).
Rosebourne Plumbing is fully G3 certified with 25+ years experience installing unvented cylinders across Hampshire and Wiltshire. We handle all Building Regulations paperwork and provide comprehensive commissioning documentation.
How to Choose the Right Size Hot Water Cylinder
Get the sizing right first time with our expert guide
| Property Type | Bedrooms | Bathrooms | Occupants | Recommended Size | Rationale |
|---|---|---|---|---|---|
| Flat/Apartment | 1-2 | 1 | 1-2 | 120-150L | One shower or bath per day |
| Terrace/Small Semi | 2-3 | 1 | 2-3 | 150-180L | Morning showers for 2-3 people |
| Semi-Detached | 3 | 2 | 3-4 | 180-250L | Multiple morning showers, evening bath |
| Detached House | 4 | 2-3 | 4-5 | 250-300L | High demand, possible simultaneous use |
| Large Detached | 5+ | 3+ | 5+ | 300L+ | Multiple bathrooms, high simultaneous demand |
Heat Pump Systems
Add 50L to recommendations above. Heat pumps heat water more slowly, so larger capacity needed for same household size.
Large Baths
Add 30-50L if you have bath >180L capacity. Standard bath = 80L. Freestanding baths = 150-250L.
Power Showers
Electric showers don't use cylinder water. Mixer showers do (8-15L/min).
Calculate Your Perfect Cylinder Size
Answer a few quick questions about your household and usage patterns to get a personalized cylinder size recommendation with product suggestions
UK Hot Water Cylinder Manufacturers Compared
With over 25 years installing hot water cylinders across Hampshire, we've worked with every major manufacturer. Here's our honest, independent assessment.
HEATRAE SADIA (MEGAFLO)
The original and still the market leader. "Megaflo" is synonymous with unvented cylinders in the UK. Premium pricing but exceptional build quality and unrivalled reliability.
GLEDHILL
Our most recommended brand for value-conscious customers. StainlessLite Plus offers 90% of Megaflo quality at 60% of the price. The "sweet spot" choice.
TELFORD
The only UK manufacturer offering a genuine LIFETIME warranty. 10% more expensive than Gledhill but you'll never buy another cylinder. ErP A+ rated.
GRANT UK
Perfect match for Grant Vortex oil boilers and Aerona heat pumps. MonoWave Slimline at 510mm diameter fits tightest spaces.
VAILLANT
Perfect integration with Vaillant ecoTEC boilers via eBUS control. uniSTOR range offers excellent heat pump compatibility (5.2m² coil).
HEAT GEEK
Designed specifically for maximum heat pump efficiency. 6.0m² coil area (LARGEST in UK) optimized for 35-40°C flow temperatures.
VIESSMANN
Bosch Group company (synergy with Worcester Bosch). Vitocell range excellent for heat pump applications. Now the "official" replacement for Worcester Bosch Greenstore cylinders.
ARISTON NUOS PLUS
Unique all-in-one solution with integrated air source heat pump INSIDE the cylinder. COP 3.14 (highest in UK). WiFi app control. 80% cheaper to run than electric immersion.
OSO HOTWATER
SHORTEST cylinders on UK market (30% less height than competitors). Perfect for low ceiling lofts or retrofit where standard cylinders won't fit. Norwegian engineering quality.
JOULE
Solid mid-range choice with 25-year warranty. Popular with regional installers. Good quality stainless steel construction. Heat pump ready models available.
LATHMORE BOILERS
Lathmore oil boilers are excellent quality. For hot water cylinders, we recommend pairing with Grant (perfect for oil), Gledhill (best value), or Telford (lifetime warranty). Any standard cylinder will work.
Recommended: Grant QR range (oil heating specialist pairing)
Need help choosing the right manufacturer? We'll recommend the best option for your specific situation.
Get Expert RecommendationVented vs Unvented: The Complete Comparison
Understanding the fundamental difference is critical. This choice affects performance, cost, and what's even possible in your property.
Side-by-Side Feature Comparison
| Feature | Vented Cylinder | Unvented Cylinder |
|---|---|---|
| Water Pressure | Gravity-fed (0.1-0.5 bar) - Low pressure | Mains pressure (1.5-3 bar) - Powerful showers |
| Loft Tank Required | Yes - Cold water tank + expansion tank needed | No - Direct from mains, no tanks |
| Installation Cost | £750-1,400 (cylinder + basic labor) | £1,600-3,500 (requires G3 certified installer) |
| Building Regulations | Standard plumbing - Any qualified plumber | G3 Unvented certification mandatory (legal requirement) |
| Multiple Outlets | Poor - Pressure drops with each tap/shower | Excellent - Run multiple showers simultaneously |
| Annual Servicing | None required | Recommended (£80-125/year) - Safety valve checks |
| Space Requirements | Large - Cylinder + loft tanks + pipework | Compact - Cylinder only (no loft tanks) |
| Freeze Risk | Moderate - Loft tanks can freeze | Low - No exposed loft pipework |
| Water Usage | No water meter concerns | High-pressure showers use more water (meter impact) |
| Property Value Impact | Neutral - Expected in older properties | Positive - Modern convenience, selling point |
| Ideal Property Type | Pre-1990s homes, low budget, gravity systems | Modern homes, renovations, multiple bathrooms |
When to Choose VENTED
Vented cylinders still make perfect sense in many situations. Here's when we actively recommend them:
Budget-Constrained Projects
If you need a cylinder replacement urgently but budget is tight, a vented copper cylinder (£750-1,400 installed) is a reliable, economical choice. You can always upgrade to unvented later.
Low Mains Pressure (<1 bar)
If your mains pressure is below 1.5 bar, an unvented cylinder won't deliver the promised performance. In rural Hampshire/Wiltshire, some properties have 0.8-1.2 bar - vented with a pump is often better.
Existing Gravity System
If you already have loft tanks and a gravity-fed system that works fine, replacing like-for-like is the most cost-effective option. No point converting the entire system if you're happy with the performance.
Single Bathroom, Low Demand
One or two occupants, single bathroom, no plans to extend - a vented cylinder will serve you perfectly well for decades. Keep it simple.
Listed Buildings / Conservation Areas
Some listed buildings or conservation properties restrict external discharge points. Vented systems have simpler overflow requirements.
💡 Will's Tip: "Don't be swayed by unvented hype if you're on a tight budget and happy with your current shower pressure. A £900 vented cylinder can outlast a £2,500 unvented if maintained properly."
When to Choose UNVENTED
Unvented cylinders transform your hot water experience. Here's when the upgrade is absolutely worth it:
Full Property Renovation
If you're gutting and renovating, this is THE time to upgrade. You'll have walls open for pipework, budget allocated, and you'll want modern performance to match your new bathroom/kitchen.
Multiple Bathrooms / En-Suites
2+ bathrooms, especially with showers - unvented is essential. Vented systems can't deliver adequate pressure to multiple outlets. Your morning routine shouldn't be a queuing system.
Loft Conversion Planned
Converting your loft? You'll lose the space for header tanks. Unvented gives you back that valuable loft space while providing better performance.
Good Mains Pressure (>1.5 bar)
If you've got strong mains pressure (most Hampshire/Wiltshire towns: Andover, Marlborough, Winchester), you're perfectly positioned for unvented. You'll get powerful, balanced flow.
Selling Within 3-5 Years
Planning to sell? "Unvented hot water system" is a genuine selling point. Buyers expect modern conveniences. The £1,500-2,000 upgrade investment adds £3,000-5,000 to perceived value.
Heat Pump Installation
If you're installing a heat pump (increasingly common with UK net zero targets), you NEED a heat pump-optimized unvented cylinder with large coil area (4.5-6.0m²). No alternative works properly.
💡 Will's Tip: "If you have the budget and good mains pressure, go unvented. In 25 years, I've never had a customer regret upgrading. Many regret NOT upgrading when they had the chance."
Building Regulations G3: What You MUST Know
Unvented cylinders operate at mains pressure (up to 3 bar). If something goes wrong, the consequences can be severe. This is why Building Regulations Part G3 exists - it's not bureaucracy, it's safety.
Legal Requirements:
G3 Certified Installer (Mandatory)
Only plumbers with G3 Unvented Hot Water certification can legally install, commission, or significantly modify unvented cylinders. This involves a 5-day training course covering safety devices, pressure calculations, and commissioning procedures.
Building Control Notification
Installation must be notified to Building Control (via installer's scheme membership or direct notification). You'll receive a compliance certificate proving the installation meets regulations.
Mandatory Safety Devices
- • Temperature Relief Valve (95°C activation)
- • Pressure Relief Valve (typically 6 bar)
- • Expansion Vessel or Internal Bubble
- • Tundish (visible discharge point)
- • Discharge Pipe (D1/D2 to safe location)
What Happens If You Ignore G3:
Insurance Invalidation
If an unvented cylinder installed without G3 certification causes damage (burst, explosion, flood), your home insurance will NOT pay out. This is explicit in most policies.
Property Sale Issues
When selling, your solicitor will ask for Building Control certification. Without it, you'll need to arrange retrospective certification (expensive) or the buyer will demand a substantial price reduction.
Safety Risk
Unvented cylinders without proper safety devices have caused serious injuries and property damage. The regulations exist because of real-world incidents.
Rosebourne Plumbing G3 Certification
Will Gaze holds G3 Unvented Hot Water certification and is registered with a competent person scheme. Every unvented installation includes:
- ✓ Compliant installation to Building Regulations Part G3
- ✓ All mandatory safety devices installed and tested
- ✓ Building Control notification and compliance certificate
- ✓ Full commissioning with performance testing
- ✓ Customer handover with safety guidance
Still not sure which is right for your property? We'll assess your mains pressure, system type, and requirements - then recommend the best option.
Get Free System AssessmentHot Water Cylinder Costs: What to Expect in 2025
Transparent pricing. No hidden costs. Based on 25+ years installing cylinders across Hampshire and Wiltshire.
Vented Copper Cylinders
| Size | Direct | Indirect | Installed Price |
|---|---|---|---|
| 90L | £180-280 | £230-380 | £650-950 |
| 120L | £220-320 | £280-420 | £750-1,100 |
| 144L | £260-360 | £320-480 | £850-1,250 |
| 210L | - | £380-510 | £1,050-1,550 |
Unvented Mid-Range (Gledhill, Telford, Grant)
| Size | Budget Option | Lifetime Warranty | Installed Price |
|---|---|---|---|
| 150L | £650-850 | £750-950 | £1,750-2,250 |
| 210L | £850-1,100 | £950-1,200 | £2,150-2,800 |
| 250L | £950-1,250 | £1,100-1,400 | £2,450-3,200 |
| 300L | £1,100-1,450 | £1,300-1,650 | £2,850-3,750 |
Heat Pump Cylinders
| Size | Cylinder Price | Installed Price | Annual Saving |
|---|---|---|---|
| 200L | £1,200-1,500 | £2,700-3,400 | £150-250 |
| 250L | £1,400-1,750 | £3,200-4,000 | £200-300 |
| 300L | £1,600-2,000 | £3,600-4,600 | £250-350 |
What's Included in Our Installation Prices
Labour & Service
Materials Included
Calculate Your Installation Cost
Get an instant estimate for your hot water cylinder installation with our live pricing calculator. Select your options to see real-time pricing, finance options, and potential savings.
Hot Water Cylinder Problems: Quick Solutions
Common issues and how to fix them
No Hot Water
No hot water at any tap/shower
Possible Causes:
- • Power off to immersion heater (direct cylinders)
- • Boiler not firing (indirect cylinders)
- • Thermostat failed
- • Timer set incorrectly
- • Isolation valves closed
Quick Fixes:
- 1. Check immersion heater power (fuse/breaker)
- 2. Check boiler is running
- 3. Check timer settings
- 4. Check isolation valves are open
- 5. Reset thermostat (button on immersion)
When to Call Us: If none of the above work (£125 call-out)
Tundish Dripping (Unvented)
Water dripping from tundish discharge point
Possible Causes:
- • Expansion vessel failed (most common)
- • Pressure relief valve faulty
- • System overpressure
- • Temperature too high
Quick Fixes:
- 1. Check boiler/immersion temperature (should be ≤65°C)
- 2. Check expansion vessel (should feel half-full when tapped)
- 3. Check mains pressure (should be <6 bar)
⚠️ NEVER cap off discharge pipe or remove tundish - serious safety hazard
Poor Shower Pressure
Weak shower performance
Possible Causes:
- • Vented system (inherently low pressure)
- • Shower head limescale
- • Cylinder too small
- • Pipework too narrow
- • Multiple outlets running
Solutions:
- 1. Clean shower head (descale)
- 2. Upgrade to unvented system (£1,600-3,000)
- 3. Install shower pump (£200-600 if vented)
- 4. Upgrade pipework to 22mm/28mm
- 5. Install larger cylinder
Free Assessment: Book pressure test - we'll diagnose exact issue
Running Out of Hot Water Quickly
Only 1-2 showers before water cold
Possible Causes:
- • Cylinder too small for household
- • Recovery time too slow (vented)
- • Immersion heater failed (one element out)
- • Boiler undersized
- • Excessive usage
Solutions:
- 1. Upgrade to larger cylinder
- 2. Upgrade to unvented (faster recovery)
- 3. Install dual immersion elements
- 4. Install heat pump cylinder (larger capacity)
- 5. Stagger shower times
Free Sizing Assessment: We'll calculate exact size needed for your household
Heat Pump Cylinders: The 2025 Specialist Guide
Planning a heat pump installation? Your cylinder choice is CRITICAL. Standard cylinders simply won't work efficiently.
Why Heat Pumps Need Special Cylinders
The Fundamental Problem:
Gas Boiler: 60-80°C Flow Temperature
Standard cylinders designed for high-temperature flow. Small coil area (1.5-2.0m²) heats water quickly at these temperatures.
Heat Pump: 35-45°C Flow Temperature
HALF the temperature of a gas boiler. A standard 1.5m² coil would take 4-6 hours to heat a cylinder - completely impractical for daily use.
⚡ Solution: Massive coil area (4.5-6.0m²) to compensate for lower flow temperatures
Real-World Impact:
❌ Standard Cylinder + Heat Pump
- • Coil area: 1.5-2.0m²
- • Reheat time: 4-6 hours
- • Recovery: 20-30L/hour
- • Result: Completely inadequate
✅ Heat Pump Optimized Cylinder
- • Coil area: 4.5-6.0m²
- • Reheat time: 45-90 minutes
- • Recovery: 80-120L/hour
- • Result: Perfect performance
Bottom line: Using a standard cylinder with a heat pump is like fitting bicycle wheels to a car - it might technically work, but it's fundamentally wrong for the application.
2025 Heat Pump Cylinder Rankings
Based on coil area, flow temperature compatibility, and real-world installer feedback. Ranked by performance with 35°C flow temperature.
| Rank | Manufacturer & Model | Coil Area | Flow Temp | Price Range | Best For |
|---|---|---|---|---|---|
🥇1 | Heat Geek Super (A-Series) | 6.0m² Industry leading | 35°C Optimal efficiency | £1,400-1,750 | Maximum efficiency, any heat pump brand |
🥈2 | Vaillant uniSTOR 250/300L | 5.2m² Excellent | 35°C Optimal efficiency | £1,300-1,600 | Vaillant aroTHERM heat pumps, smart home integration |
🥉3 | Viessmann Vitocell 200-W/V | 4.5m² Very good | 40°C Good performance | £1,200-1,500 | Viessmann/Worcester Bosch heat pumps, German quality |
| 4 | Grant UK Wave HP 250L | 4.2m² Good | 40°C Good performance | £1,200-1,500 | Grant Aerona heat pumps, rural installations |
| 5 | Heat Geek Super (B-Series) | 4.0m² Compact option | 35°C Optimal efficiency | £1,450-1,800 | Height-restricted installations, tight spaces |
| 6 | Ariston Nuos Plus 250L | Built-in HP Integrated system | N/A Self-contained | £1,800-2,400 | Retrofit, no external heat pump needed |
Understanding Coil Area Impact:
6.0m² Coil (Heat Geek)
250L reheat: 45-60 minutes @ 35°C
4.5m² Coil (Viessmann)
250L reheat: 70-90 minutes @ 40°C
1.5m² Coil (Standard)
250L reheat: 4-6 hours @ 35°C ❌
Critical Installation Considerations
Size Up by 50L Minimum
Heat pumps heat more slowly than gas boilers. If a 200L cylinder would work with gas, specify 250L minimum for heat pump. The extra capacity compensates for slower recovery.
Match Cylinder to Heat Pump Brand
While any heat pump cylinder will work, matching brands (Vaillant aroTHERM + uniSTOR, Grant Aerona + Wave HP) gives better integration, smart controls, and unified warranty.
Don't Skimp on Coil Area
The £200-300 difference between a 4.2m² and 6.0m² coil is nothing compared to the £8,000-12,000 heat pump investment. Get the best cylinder to maximize your heat pump efficiency.
Future-Proof Your Choice
Even if you're not installing a heat pump now, specifying a heat pump-ready cylinder (4.5m²+) means you're prepared for future conversion. It costs little extra and adds system value.
Will's Heat Pump Cylinder Recommendations
🏆 Best Overall: Heat Geek Super A-Series
6.0m² coil is unmatched. Works brilliantly with any heat pump brand at 35°C flow temps. This is what I install in my own home and recommend to family.
£1,400-1,750 | Worth every penny
💰 Best Value: Viessmann Vitocell 200
4.5m² coil is excellent, especially if you already have Worcester Bosch or Viessmann equipment. £1,200-1,500 represents great value for the quality.
🔗 Best Ecosystem: Vaillant uniSTOR
If you're committed to Vaillant aroTHERM heat pump, the uniSTOR 250/300L with 5.2m² coil integrates beautifully via eBUS controls. Seamless smart home setup.
🌾 Best for Rural: Grant Wave HP
Perfect pairing with Grant Aerona heat pumps, popular in off-gas rural Hampshire/Wiltshire. 4.2m² coil is adequate, and Grant's rural support network is excellent.
💡 Free Heat Pump Cylinder Consultation: We'll specify the perfect cylinder for your heat pump model and household needs.
Planning a heat pump installation in Hampshire or Wiltshire? Let's discuss the right cylinder specification for your project.
Book Heat Pump Cylinder ConsultationLocal Water Considerations for Hampshire & Wiltshire
Hard water impacts your cylinder choice - here's what you need to know
Hampshire Water Hardness: VERY HARD
300-400mg/L CaCO3
Areas Most Affected:
- • Andover: Very Hard
- • Basingstoke: Very Hard
- • Winchester: Very Hard
- • Test Valley: Very Hard
- • Salisbury: Hard
- • Marlborough: Hard
What This Means for Your Cylinder
Our Recommendations for Hard Water
1. STAINLESS STEEL CYLINDERS (not copper)
- • Better limescale resistance
- • Longer lifespan
- • Less maintenance
2. REGULAR DESCALING
- • Every 5 years recommended
- • Cost: £150-250
- • Restores efficiency
3. WATER SOFTENER CONSIDERATION
- • Whole house: £800-1,500 installed
- • Protects all appliances
- • Extends cylinder life 5-10 years
- • ROI: 3-7 years
Hard Water Savings:
- • Softened water: Cylinder lasts 20+ years
- • Hard water: Cylinder lasts 12-15 years
- • Annual saving: £150-300 (efficiency + lifespan)
Best Choices for Hampshire Hard Water
TELFORD HURRICANE
Stainless steel construction
Lifetime warranty
£950-1,650 (210-300L)
GLEDHILL STAINLESSLITE
Stainless steel
25-year warranty
£850-1,450 (210-300L)
MEGAFLO ECO
Duplex stainless steel (316L)
25-year warranty
£1,800-2,700 (210-300L)
Helpful Resources & Tools
Download guides, use our calculators, and watch installation videos
Quick Reference PDF
Download our comprehensive cylinder sizing and specification guide. Perfect for planning your installation with your builder or architect.
- • Sizing chart by property type
- • Manufacturer comparison table
- • Building Regulations checklist
- • Installation timeline
Size Calculator
Not sure what size you need? Our interactive calculator asks about your household and recommends the perfect cylinder size.
Example: 4-bed detached, 2 bathrooms, family of 4 = 250L unvented
Installation Videos
Watch Will explain cylinder choices, installation processes, and what to expect during your upgrade project.
- • Unvented vs vented explained
- • Heat pump cylinder guide
- • Installation day walkthrough
- • Maintenance tips
Still Have Questions?
📞 Free Phone Consultation
Call Will directly for expert advice. No sales pressure - just honest guidance on the best cylinder for your situation.
01264 502027📧 Email Your Specs
Send us your property details and we'll email back with specific recommendations and accurate pricing within 24 hours.
Get Email QuoteWhy Choose Rosebourne Plumbing for Your Cylinder Installation?
25+ years installing hot water cylinders across Hampshire & Wiltshire
Will Gaze
Owner & Lead Installer
G3 Certified • 25+ Years Experience
I've been installing hot water cylinders across Hampshire and Wiltshire since 1998. In that time, I've fitted hundreds of cylinders - from budget vented coppers to premium Megaflos and cutting-edge heat pump systems.
G3 Unvented Certified
Fully qualified for Building Regulations Part G3 compliance
Manufacturer Trained
Certified installer for Megaflo, Gledhill, Vaillant, Grant UK
Heat Pump Specialist
Extensive experience with heat pump cylinder installations
Local Knowledge
Understanding Hampshire's hard water challenges
"I don't just install cylinders - I help you choose the right one. Too many customers end up with oversized (wasting money) or undersized (daily frustration) systems. Let's get it right first time."
- Will Gaze, Rosebourne Plumbing
What Our Customers Say
"Will replaced our ancient vented cylinder with a Gledhill unvented system. The difference is incredible - powerful showers, no more running out of hot water. He explained everything clearly and the installation was spotless."
Sarah M.
Andover - 250L Gledhill Unvented Installation
"We're installing a heat pump and Will specified the perfect cylinder - Heat Geek Super with 6.0m² coil. His knowledge of heat pump systems saved us from a costly mistake. Highly recommended."
James & Emma T.
Winchester - Heat Pump Cylinder Specification
"Honest advice - Will actually recommended we stick with our vented system rather than spending £2,500 on unvented. He saved us money when he could have sold us an expensive upgrade. That's integrity."
David R.
Marlborough - Cylinder Consultation
5.0 Average Rating
Based on 150+ cylinder installations
Read more reviews on Google, Checkatrade, and Trust Pilot
Hampshire & Wiltshire Coverage
We install hot water cylinders throughout Hampshire, Wiltshire, and parts of Berkshire
Hampshire
- Andover
- Winchester
- Basingstoke
- Whitchurch
- Test Valley
Wiltshire
- Marlborough
- Salisbury
- Pewsey
- Tidworth
- Amesbury
Berkshire
- Newbury
- Hungerford
- Thatcham
- Kintbury
Rural Areas
- All villages
- Off-gas properties
- Oil heating systems
- Heat pump installs
Not sure if we cover your area? Contact us - we're often happy to travel for larger projects.
The Rosebourne Difference
Full Compliance
G3 certified, Building Control notification, all safety devices installed and tested
Quality Guaranteed
We only fit cylinders we'd install in our own homes. No cutting corners, no cheap alternatives
Local & Trusted
25 years serving Hampshire & Wiltshire. Your neighbors have probably used us
Ready to Upgrade Your Hot Water System?
Get a free, no-obligation quote from Hampshire's hot water cylinder specialists