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G3 qualified engineer installing a Joule Cyclone unvented hot water cylinder in a London property
Joule Approved Installer — G3 Qualified

Joule Cyclone Installation London

Slim and Standard duplex stainless steel cylinders, 125L–300L, fitted across all 32 London boroughs from £1,495. G3 qualified engineers, Building Regulations Part G3 notification, 25-year Joule tank warranty registered on your behalf.

Free on-site survey within 48 hours. Fixed-price quote in writing. Most installs completed in a single day. Annual G3 services from £155.

0207 046 1363WhatsApp 07456 975436Book online
25yr Tank warranty
G3 Qualified engineers
£1,495 From fitted
475mm Slim option
1 day Typical install
Quick Answer

Joule Cyclone is a duplex stainless steel unvented cylinder fitted across London from £1,495 (125L Slim) to £2,595 (300L Standard). Slim 475 mm variant fits pre-2000 narrow airing cupboards where a standard cylinder will not. Every install is carried out by a G3 qualified engineer, notified under Building Regulations Part G3, and ships with a 25-year tank warranty and an annual service plan from £155.

What is a Joule Cyclone unvented cylinder?

The Joule Cyclone is a duplex 2304 stainless steel unvented hot water cylinder manufactured in Ireland. It is the principal direct competitor to the Heatrae Sadia Megaflo Eco in the UK market — same construction, same 25-year tank warranty, same layered safety design, around 5–10% cheaper fitted. Joule sells through Wolseley, Plumb Center and City Plumbing in London, which keeps parts and replacements available across every borough.

The Cyclone comes in two diameters: Slim at 475 mm for narrow airing cupboards and flat-conversion alcoves, and Standard at 550 mm for normal cupboard widths. Capacities run from 125L (1-bed flat) to 300L (5-bed family home or HMO). Variants include indirect (coil heated by a system boiler), direct (twin electric immersions for off-gas properties), solar twin-coil, and heat-pump compatible models.

Like every unvented cylinder over 15 litres, the Joule Cyclone is a controlled service under Approved Document G3 of the Building Regulations. The install must be carried out by a G3 qualified engineer, notified to building control directly or via a competent person scheme, and commissioned with a benchmark logbook. Skipping any of those steps voids the Joule 25-year warranty and the home insurance.

Joule Cyclone sizing guide — Slim vs Standard

The two big questions are how much hot water do you need and will it fit the cupboard. The table below maps every Cyclone model to its typical London property.

ModelDiameterHeightSuits
Cyclone Slim 125L475 mm1,205 mm1-bed flat, narrow airing cupboard, single bath.
Cyclone Slim 150L475 mm1,395 mm2-bed flat, single shower, tight cupboard footprint.
Cyclone Slim 170L475 mm1,535 mm2–3 bed flat, en-suite + main bath, slim airing cupboard.
Cyclone Standard 150L550 mm1,100 mm2-bed terrace, single bath, standard cupboard.
Cyclone Standard 170L550 mm1,220 mm3-bed terrace, 1–2 occupants per bedroom, one bath.
Cyclone Standard 200L550 mm1,395 mm3-bed family home, single bath + en-suite shower.
Cyclone Standard 250L550 mm1,675 mm4-bed family home, 2 baths, simultaneous use.
Cyclone Standard 300L580 mm1,920 mm5-bed / 3-bath / freestanding bath / HMO.

Heights quoted are nominal — full schematic dimensions confirmed against the cupboard on the free survey.

Joule Cyclone installation cost London — 2026 prices

Every quote is a fixed figure given on site after the 30-minute survey. No call-out fee on quoted work, no parking add-ons, no day-rate creep, no out-of-hours premium on scheduled installs. Vented-to-unvented conversion adds £350–£500 depending on access and discharge route.

JobWhat's includedTypical cost
Joule Cyclone Slim 150L indirect — fittedSupply & fit slim-line indirect cylinder (475 mm dia.), full G3 inlet group, expansion vessel, tundish, discharge to outside, commissioning certificate, Building Regs notification.£1,595
Joule Cyclone Standard 170L indirect — fittedSupply & fit 170L indirect (550 mm dia.), all safety devices, primary connections to system boiler, benchmark logbook, 25-year tank warranty registered.£1,695
Joule Cyclone Standard 200L indirect — fittedSupply & fit 200L indirect for 3-bed family home, full G3 kit, like-for-like swap, commissioning + Compliance Certificate.£1,845
Joule Cyclone Standard 250L indirect — fittedSupply & fit 250L indirect for 4–5 bed / 2-bath home, mains-pressure check, full safety group, secondary circulation tee left if specified.£2,195
Joule Cyclone Standard 300L indirect — fittedSupply & fit 300L indirect for large family home or HMO, full G3 group, dynamic flow test, written sizing report.£2,595
Joule Cyclone Direct (electric) 150L — fittedSupply & fit twin-immersion direct cylinder for off-gas properties, dedicated immersion circuits, dual-thermostat commissioning.£1,545
Joule Cyclone Solar 250L (pre-plumbed) — fittedSupply & fit solar-ready twin-coil cylinder, lower coil for solar thermal / heat pump, upper coil for boiler, immersion backup.£2,495
Vented to Joule Cyclone unvented conversion (180L)Remove old vented cylinder + loft tank, run new mains to cylinder location, fit Cyclone with full G3 group, new discharge route to outside, certificate.From £2,795
Joule Cyclone annual G3 serviceExpansion vessel pre-charge reset, T&P witnessed lift, PRV outlet test, immersion resistance, anode inspection, benchmark logbook refresh.£155
Labour-only Cyclone install (customer-supplied)Fit a customer-supplied Joule Cyclone with G3 cert, benchmark logbook, building control notification. Inlet group + discharge fittings extra at cost.From £695

Prices include VAT, materials, removal and disposal of the old cylinder, full G3 inlet group, commissioning, benchmark logbook, Building Regulations notification and 12-month workmanship guarantee. See the full pricing page.

Free survey within 48 hours.

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Joule Cyclone vs Megaflo, Telford and Gledhill

All four brands are duplex stainless steel cylinders with 25-year tank warranties. Differences are practical — price, parts coverage on London vans and slim-line availability.

Joule Cyclone unvented hot water cylinder fitted in a London airing cupboard

Joule Cyclone

£1,495–£2,595 fitted

Construction: Duplex 2304 stainless steel (Irish-made), 50 mm rigid PU foam jacket.

Warranty: 25 years tank, 2 years parts.

Strength: Slim 475 mm option that beats Megaflo Slimline on price. Strong availability through Wolseley / Plumb Center London branches.

Megaflo Eco

£1,595–£2,845 fitted

Construction: Duplex stainless steel, factory-foamed.

Warranty: 25 years tank, 2 years parts.

Strength: UK market leader. Best parts coverage on London vans. Premium price.

Telford Tempest

£1,545–£2,695 fitted

Construction: Duplex stainless steel.

Warranty: 25 years tank, 5 years parts.

Strength: Best parts warranty in the range. Strong on heat-pump and Mixergy-compatible options.

Gledhill StainlessLite Plus

£1,565–£2,745 fitted

Construction: Duplex stainless steel.

Warranty: 25 years tank, 2 years parts.

Strength: Fast recovery time. Welsh-made. Strong on direct-electric and solar-ready models.

For comparison alternatives see our Megaflo replacement and Telford Tempest installation pages, or read the 2026 cylinder cost guide.

Installation process — survey to certificate

1

Survey & sizing

30–45 min

Free on-site survey. Static and dynamic mains pressure measured, cylinder location agreed, discharge route to outside walked, G3 paperwork pre-filled. Written fixed-price quote sent within 24 hours.

2

Isolation & strip-out

45–60 min

Mains isolated, cylinder drained from immersion boss, old unit decommissioned. On vented-to-unvented jobs the loft tank and feed/expansion pipework come down on the same visit.

3

Cyclone fit & pipework

2–3 hours

Joule Cyclone positioned, secured, all primary and secondary pipework in copper to BS EN 1057. Inlet group (isolator, strainer, PRV, single check valve, expansion connection) fitted on the cold mains. 22 mm discharge from tundish in copper, continuous fall to outside.

4

Commissioning & test

45–60 min

System filled, vented, pressurised. Expansion vessel pre-charged to 3.0 bar with system depressurised. T&P relief valve witnessed-lifted. PRV outlet set to 3.0–3.5 bar. Stored temperature run up to 60°C. Energy cut-out function tested.

5

Handover & paperwork

20–30 min

Benchmark logbook completed. G3 Compliance Certificate notified via WaterSafe / BESCA, posted within 30 days. 25-year tank warranty registered with Joule on the customer's behalf. Photos of every commissioning step emailed for the records.

G3 compliance & Benchmark commissioning

Every Joule Cyclone install is treated as a controlled service under Approved Document G3 of the Building Regulations. The paperwork trail is as important as the pipework — the 25-year tank warranty, your home insurance and the property's building control history all depend on it.

Tundish, temperature and pressure relief valve and G3 inlet group on a Joule Cyclone unvented cylinder

G3 ticket on file

Every engineer holds a current BPEC HWSS / G3 certificate, renewed every five years. Ticket numbers on the Compliance Certificate.

Building Control notification

Self-certified via WaterSafe Competent Persons Scheme. No need for the homeowner to deal with local authority Building Control directly.

Benchmark logbook

Manufacturer's commissioning logbook completed in full on the day — required to validate the 25-year Joule tank warranty.

Water Regulations notification

Where the install changes the system arrangement, the local water undertaker is notified in line with the Water Supply (Water Fittings) Regulations 1999.

Discharge pipe to AD-G

Tundish and D2 discharge piped to a visible, safe outside termination — sized one pipe larger than the T&P inlet, continuous fall, maximum equivalent length per the manufacturer's table.

Compliance Certificate

Building Regulations Part G3 Compliance Certificate posted within 30 days. Held on file for the property — required at sale and on EICR-style inspections.

Need the regulatory detail? Read the G3 engineer explainer or call 0207 046 1363 to speak to a qualified engineer directly.

Recent London Cyclone installs — worked examples

Every London property is different. Five anonymised installs from the last twelve months, with the diagnostic call, the work done and the final figure inc. VAT.

2-bed flat, Clapham — Cyclone Slim replacing a leaking Tribune HE

1990s flat with a tight airing cupboard (480 mm wide). Existing 150L Range Tribune HE leaking from the lower seam. Joule Cyclone Slim 150L (475 mm dia.) dropped into the same footprint with 22 mm copper repipe on the primary. Vented-to-unvented work already done in 2008, so the discharge route was reused. Half-day install. Final invoice: £1,595 inc. VAT.

3-bed Victorian terrace, Hackney — Cyclone Standard 200L like-for-like swap

12-year-old Megaflo CL Indirect 180L with a waterlogged vessel and pinhole leak around the immersion boss. Customer wanted to keep Joule (the original install brand on the street). Cyclone Standard 200L fitted in 5.5 hours, mains pressure tested at 3.4 bar dynamic, full G3 group renewed. Final invoice: £1,845 inc. VAT.

4-bed family home, Wandsworth — vented to Cyclone 250L conversion

1970s house with a copper vented cylinder + loft tank + immersion. Customer added a power shower in a loft conversion and pressure was unusable. Full vented-to-unvented conversion: loft tank removed, new 22 mm mains run to cylinder, Cyclone Standard 250L fitted, new discharge through external wall, building control notified. Two-day install. Final invoice: £3,395 inc. VAT.

Top-floor flat, Camden — Cyclone Slim 170L in a freeze-prone airing cupboard

Existing 1990s Megaflo failing — anode spent, vessel waterlogged for the third time. Slim 170L Cyclone fitted with a Hotun dry-trap on the discharge to avoid freeze-back through the loft soffit. Lagging upgraded on the cold inlet within 600 mm of the vessel. Final invoice: £1,795 inc. VAT.

HMO licensed property, Tower Hamlets — Cyclone 300L for 6-bed share

Landlord upgrading an old 210L to handle six tenants with three showers. Cyclone Standard 300L fitted with secondary return tee for future ring-main, twin TMV2 cartridges on the shower outlets capped to 43°C. HMO licence file updated with the new G3 certificate and benchmark logbook. Final invoice: £2,895 inc. VAT.

Free Joule Cyclone survey this week

G3 qualified engineer to your door within 48 hours. Cupboard measured, mains pressure tested, discharge route walked, fixed-price quote in writing within 24 hours. Free, no obligation.

Call 0207 046 1363WhatsApp 07456 975436Book online

Joule Cyclone — frequently asked questions

What is a Joule Cyclone cylinder and why choose it for a London install?
Joule Cyclone is a duplex 2304 stainless steel unvented cylinder manufactured in Ireland by Joule Group. It is the closest direct competitor to Megaflo Eco at a lower fitted price, with the same 25-year tank warranty and equivalent inlet group. For London the strongest argument is the Slim 475 mm range — most pre-2000 airing cupboards in flats are too narrow for a standard 550 mm cylinder, and the Slim Cyclone drops into the same footprint as an old Tribune HE or first-generation Megaflo Slimline. Parts availability through Wolseley and Plumb Center is reliable across all London branches.
How much does a Joule Cyclone installation cost in London?
Like-for-like fitted prices in 2026 run from £1,495 for a Cyclone Slim 125L up to £2,595 for the Standard 300L. The mid-range — 180L–210L Standard — is the most-installed size for 3–4 bed London homes at £1,745–£1,895 fitted. Prices include the cylinder, full G3 inlet group, expansion vessel, tundish and discharge pipework, commissioning, Building Regulations G3 notification, benchmark logbook, removal of the old cylinder and 12-month workmanship guarantee. Vented-to-unvented conversions add £350–£500.
What is the difference between the Cyclone Slim and Cyclone Standard?
The Slim range is 475 mm in diameter, designed to fit pre-2000 narrow airing cupboards and tight London flat-conversion alcoves. It runs taller per litre than the Standard to compensate. The Standard range is 550 mm in diameter and is the right choice when the cupboard has the width and you want lower height — useful when there is a sloping ceiling above or a built-in shelf. Performance and warranty are identical. Slim costs roughly 4–6% more for the same capacity to cover the more complex manufacturing.
Do I need a G3 ticket to install a Joule Cyclone?
Yes. Approved Document G3 of the Building Regulations makes the installation, commissioning and modification of any unvented hot water vessel over 15 litres a controlled service. The engineer must hold a current G3 qualification (BPEC HWSS, LCL Awards or City & Guilds 6189) and the work must be notified to building control directly or through a competent person scheme. A non-G3 install voids the Joule 25-year tank warranty, the home insurance and the building control trail. Every ERL engineer carries an in-date G3 ticket — number printed on every certificate.
How long does a Joule Cyclone install take?
A like-for-like swap of an existing unvented cylinder takes 4–6 hours in a single day — strip-out, fit, repipe, commission, paperwork. A vented-to-unvented conversion is a 1–2 day job because the loft tank, feed/expansion pipework, new mains run and discharge route to outside are all new work. The variables in London are access (top-floor flats, rooftop cylinder cupboards in mansion blocks) and the discharge route — the tundish discharge must reach outside with a continuous fall and a maximum equivalent length, which is sometimes the hardest engineering question.
How is a Joule Cyclone different from a Megaflo?
Both are duplex stainless steel unvented cylinders with 25-year tank warranties and a 2-year parts warranty. The differences are practical. Megaflo Eco has stronger parts coverage on London plumber vans — vessels, PRVs and elements are stocked everywhere. Joule Cyclone is around 5–10% cheaper fitted and the Slim 475 mm range is wider than Megaflo's Slimline equivalent. Inlet group connections are interchangeable, so a swap from one to the other rarely needs repipe work. For most London 2–4 bed homes the choice is price-led — Cyclone if budget matters, Megaflo if parts speed matters.
What size Joule Cyclone do I need?
Rule of thumb in London: 35–45 litres of storage per occupant, plus 50 litres for properties with a bath used daily. A 1–2 bed flat with a shower is fine on Cyclone Slim 150L. A 3-bed family home with one bath is Standard 200L. A 4–5 bed home or any property with two or more bathrooms wants Standard 250L–300L. HMOs and homes with secondary circulation are sized against simultaneous-use loadings using the Joule flow curve, not a rule of thumb. We confirm the sizing in writing on the quote.
Will my existing pipework work with a Joule Cyclone?
If the property already has an unvented system, almost always yes. The Cyclone uses 22 mm primary connections and standard G3 inlet group fittings on the cold side. The only common issue on like-for-like swaps is a tired expansion vessel and PRV — we replace both as part of the install rather than reuse. On vented-to-unvented conversions the entire cold supply, discharge and electrical work is new. We run a 22 mm dedicated mains feed to the cylinder location and a new discharge to outside.
Does Joule Cyclone come with a 25-year warranty?
The duplex stainless steel tank carries a 25-year warranty from Joule on condition the cylinder is installed by a G3 qualified engineer, commissioned with the benchmark logbook completed, and serviced annually. Components (immersion, thermostat, PRV, expansion vessel, T&P valve) carry a 2-year warranty. Missing an annual service is the most common reason warranty claims are rejected, so we automatically send a reminder 11 months after install.
Can I have a Joule Cyclone in a top-floor flat?
Yes — they are common in London top-floor flats because they avoid loft tanks and freeze risk. The two checks are mains inlet pressure (must be at least 1.5 bar dynamic at the inlet group) and a viable discharge route to outside. The Slim 475 mm range is particularly suited to top-floor airing cupboards. In some mansion blocks the discharge route is the hardest engineering question — the cylinder may need to live closer to an external wall than the previous cupboard, or the discharge piped through a fire-rated metallic duct to a soffit.
Do I need to notify Building Control for a Cyclone install?
Yes — every unvented cylinder install is notifiable under Part G3 of the Building Regulations. We self-certify via the WaterSafe Competent Persons Scheme, which means the homeowner does not need to deal with the local authority directly. The Compliance Certificate is posted to the property address within 30 days and held on the National Building Register. This is the document estate agents and conveyancers ask for at sale.
What is the difference between direct and indirect Joule Cyclone?
Indirect Cyclone has a primary coil inside the cylinder heated by an external boiler (or heat pump). Used on any property with a working system or combi-replacement-to-system upgrade. Direct Cyclone has no coil — the water is heated by twin electric immersion heaters. Used on off-gas or all-electric properties. Direct is around £100–£150 cheaper to install but more expensive to run on electric tariffs. Most London installs are indirect because most homes have a gas system boiler feeding the cylinder.
What annual service does a Joule Cyclone need?
An annual G3 service. Twelve-point check: expansion vessel pre-charge tested and reset to manufacturer spec; T&P relief valve witnessed-lifted; PRV outlet pressure measured and adjusted; inlet strainer cleaned; tundish gap and discharge route visually checked; immersion element resistance measured; thermostat cut-out tested; anode inspected; cold inlet pressure logged; stored water temperature logged; benchmark logbook refreshed; certificate emailed within 24 hours. £155 fixed for a single cylinder in London.
Can I switch from a Megaflo or Telford to a Joule Cyclone?
Yes — and on a like-for-like swap it is one day's work. The Megaflo and Telford inlet groups, primary connections and discharge route are all transferable to a Cyclone with minimal pipework changes. The main reason to switch is cost (Cyclone is 5–10% cheaper fitted) or to fit a Slim 475 mm where the original cylinder was overspec for the cupboard. We always renew the inlet group and expansion vessel on a brand swap rather than reuse — it is a clean compliance line and the parts are budgeted in.
Where do you cover for Joule Cyclone installs?
All 32 London boroughs and the City. Heaviest install volumes in Camden, Islington, Hackney, Wandsworth, Lambeth, Southwark, Kensington & Chelsea and Hammersmith & Fulham. Two G3 vans on standby for same-week installs across Zone 1–3. Free survey within 48 hours of the first call. Quote is fixed in writing before any work begins — no day-rate creep, no parking surcharges, no out-of-hours premium on scheduled installs.

Question not answered? Call 0207 046 1363 and talk to a G3 qualified engineer directly — no call centre, no triage.

Service area

Joule Cyclone installs across all London boroughs

G3 qualified Joule installers based in central London with same-week install slots across all 32 London boroughs and the City. Two dedicated cylinder vans on standby.

Ready to fit a Joule Cyclone?

G3 qualified engineers across London. Free survey within 48 hours. Fixed-price written quote inside 24 hours. From £1,495 fitted with Building Regulations G3 notification and 25-year Joule tank warranty. £5M public liability, fully insured.

0207 046 1363WhatsApp 07456 975436Book online

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