Hot Water Cylinder Replacement London
Vented, unvented, or immersion — we replace hot water cylinders across London. G3-qualified engineers for unvented systems. Fixed prices, same-day emergency response, no call-out fee.
🚨 Cylinder leaking right now?
- Close the gate valve on the cold feed pipe to the cylinder (or tie up the loft ball valve)
- Switch off the immersion heater isolator switch
- Turn off the boiler if it heats the cylinder
- Place towels under the leak — call us: 020 7870 3200
Vented vs. Unvented vs. Immersion — Which Do You Have?
London homes span every era of plumbing. Victorian terraces in Hackney may have copper vented cylinders from the 1980s; new-build flats in Nine Elms have unvented megaflow cylinders. We replace them all.
Vented (Indirect) Cylinder
Gravity-fed from a cold water tank in the loft. The most common type in pre-2000 London homes. Water is heated by the boiler via a coil inside the cylinder. Lower pressure but reliable.
✓ Simpler installation ✓ Lower cost ✓ No G3 cert required ✓ Tolerates low mains pressure
✗ Low shower pressure on upper floors ✗ Loft tank takes up space ✗ Gravity limits flow rate
Typical size: 120–210 litres typical
£650–£950 supply & fit
Unvented (Mains Pressure) CylinderUpgrade Choice
Connected directly to the mains — no loft tank needed. Delivers hot water at full mains pressure (3–4 bar). The upgrade choice for London homes with poor shower pressure. Requires G3 qualified engineer.
✓ Mains-pressure hot water ✓ No loft tank needed ✓ Excellent shower flow ✓ Faster recovery
✗ Higher installation cost ✗ Requires G3 certification ✗ Expansion vessel needs annual check
Typical size: 120–300 litres
£1,200–£2,000 supply & fit
Electric Immersion Cylinder
Heated by an electric immersion heater element — no boiler required. Common in flats without gas supply and as a backup in vented systems. Off-peak Economy 7 tariff can reduce running costs.
✓ No gas needed ✓ Backup when boiler fails ✓ Economy 7 compatible ✓ Simple controls
✗ Higher running cost than gas ✗ Slower to heat ✗ Limescale on element in London
Typical size: 120–180 litres typical
£145–£180 element only; £650+ full cylinder
Signs Your Cylinder Needs Replacing
| Symptom | Likely cause | Repair or replace? |
|---|---|---|
| Visible leak from cylinder body | Pitted copper or corroded seam | Replace — pitted copper cannot be repaired |
| Rusty / discoloured hot water | Internal corrosion, sacrificial anode exhausted | Replace if severe; anode replacement if early stage |
| Hot water runs out in 10–15 mins | Undersized, faulty thermostat, or failing element | Diagnose first — may be thermostat or element (£85–£180) |
| Cylinder over 20 years old + leaking | Age-related failure | Replace — unlikely to be economical to repair |
| PRV (pressure relief valve) constantly dripping | Expansion vessel failed (unvented) | Replace expansion vessel (£120–£160) before cylinder |
| Banging / kettling noise when heating | Heavy limescale inside (London hard water) | Power flush or descale — or replace if severe |
Cylinder Replacement Prices — London 2026
| Job | Time | Price (supply & fit) |
|---|---|---|
| Vented copper cylinder replacement (like-for-like, 120–150L) | Half day | £650–£850 |
| Vented copper cylinder replacement (180–210L) | Half day | £800–£950 |
| Unvented cylinder replacement (120–150L) | Full day | £1,200–£1,600 |
| Unvented cylinder replacement (200–300L) | Full day | £1,500–£2,000 |
| Vented to unvented conversion (remove loft tank) | 1–2 days | £1,400–£2,200 |
| Immersion heater element replacement | 45–60 min | £145–£180 |
| Immersion heater thermostat replacement | 30–45 min | £85–£110 |
| Cylinder thermostat / programmer replacement | 30–45 min | £85–£120 |
| Pressure relief valve replacement (unvented) | 30–45 min | £95–£130 |
| Expansion vessel replacement (unvented) | 45–60 min | £120–£160 |
All prices include removal of old cylinder, installation, pipework connections, and commissioning. G3 Building Regulations notification included for unvented work. No call-out fee.
Cylinder Replacement Across All London Boroughs
G3-qualified engineers covering every London borough. Survey visits within 24 hours. Most cylinder replacements completed in a single day.
Hot Water Cylinder FAQs
How much does hot water cylinder replacement cost in London?
Hot water cylinder replacement in London costs £650–£2,000 fully fitted, depending on the cylinder type. A vented copper cylinder (indirect, gravity-fed) is £650–£950 supply and fit. An unvented cylinder (mains-pressure) is £1,200–£2,000 supply and fit, plus G3 Building Regulations notification. Immersion heater element replacement is £145–£180.
What's the difference between a vented and unvented cylinder?
A vented (indirect) cylinder relies on a cold water tank in the loft for pressure — gravity-fed, lower pressure at taps. An unvented cylinder connects directly to the mains and delivers water at full mains pressure (3–4 bar) — much better shower performance. Unvented installation requires a qualified G3-certificated engineer and Building Regulations notification. We are G3 qualified.
How long does a hot water cylinder last?
A well-maintained copper cylinder lasts 20–25 years. Unvented stainless steel cylinders can last 25–30 years. London's hard water (280–320 mg/l) accelerates limescale buildup inside the cylinder and on the immersion element — reducing efficiency and lifespan. Annual servicing of the pressure relief valve and expansion vessel (unvented) extends life significantly.
My cylinder is leaking — what should I do?
Turn off the cold water supply to the cylinder at the gate valve or ball valve on the cold feed pipe. For vented cylinders, also tie up the ball valve in the cold water tank. Switch off the immersion heater at the isolator switch. Place towels or a bucket under the leak and call us — a leaking cylinder usually needs replacement.
Can I switch from a vented to an unvented cylinder?
Yes — this is one of the most popular upgrades we do in London homes. You remove the cold water tank from the loft (freeing up loft space), connect the cylinder directly to the mains, and gain full-pressure hot water throughout the property. The work takes one day and costs £1,400–£2,200 including G3 certification. Particularly effective for top-floor flats where gravity pressure is especially poor.
Why is my hot water running cold after 10–15 minutes?
Running out of hot water quickly usually means the cylinder is undersized for your household, the thermostat is set too low (should be 60°C), or the immersion element is failing. Heavy limescale buildup on the element — very common in London — can also reduce heating efficiency significantly. We'll diagnose on arrival.
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Need a New Hot Water Cylinder?
G3 Qualified · Vented & Unvented · Supply & Fit · All London
📞 Call 020 7870 3200