Megaflo Installation London — Eco 70L to 300L, From £1,495 Fitted
G3 qualified Heatrae Sadia specialists across all 32 London boroughs. Megaflo Eco supply, fit, replacement and vented-to-unvented conversion. 25-year tank warranty preserved. Building Regulations Part G3 notification and Benchmark commissioning included on every install.
Free on-site survey within 48 hours. Fixed written price the same day. Most like-for-like swaps booked and completed within 5 working days.
The Megaflo Eco is the UK's bestselling unvented hot water cylinder, made by Heatrae Sadia in sizes 70L to 300L. London installs run from £1,495 fitted for the 125L through to £2,595 fitted for the 300L, including the G3 inlet group, expansion vessel, T&P discharge, Benchmark logbook and Building Regulations notification. The bestseller for 2–3 bed London properties is the 170L Indirect Plus at £1,745 fitted.
What is the Megaflo Eco?
The Megaflo Eco is Heatrae Sadia's flagship duplex stainless steel unvented hot water cylinder, sold across the UK in sizes from 70L to 300L. It has been the bestselling unvented cylinder in Britain for over a decade — for good reasons. Heatrae Sadia operates the deepest UK service network of any cylinder manufacturer: almost every G3 engineer in London carries Megaflo expansion vessels, PRVs and immersion elements as standard van stock, and parts ship next-day from the Heatrae Sadia distribution centre to every London merchant.
The Eco variant — current since 2014 — adds a thicker factory-foamed insulation jacket, dropping standing heat loss to roughly half of pre-2010 cylinders. Most sizes are ErP Class B labelled, with the 70L slimline coming in at 0.62 kWh per 24 hours. The duplex stainless steel tank is rated to 12 bar (regulated down to 3.0–3.5 bar at the inlet group) and carries Heatrae Sadia's 25-year manufacturer warranty when commissioned and serviced annually by a G3-qualified engineer.
Two heating configurations matter at quote stage. The Indirect Plus is heated by a primary coil fed from a system or heat-only boiler — this is the right model for the 90% of London properties on gas central heating. The Direct is heated by electric immersion elements only, used in all-electric flats with no gas connection. Both have a SystemFit option with a factory-fitted pre-plumbing jig that saves 60–90 minutes on the install where the airing cupboard layout suits it. Beyond that, the Megaflo Eco range also includes SolarPlus (twin-coil solar-thermal) and HeatPump (large coil for ASHP) variants.
Megaflo Eco range — sizing guide for London properties
The right size depends on bedrooms, bathrooms, occupants and how the property uses hot water. The Hot Water Association rule of thumb — 35–45 litres per person, plus 50 litres for a regularly used bath — gets you within one size of the right answer. The remaining variables are simultaneous-use loadings (two showers running at once), the boiler output driving the indirect coil, and dynamic mains pressure at the inlet group.
| Model | Use case | Spec notes | Reheat |
|---|---|---|---|
| Megaflo Eco 70L | Studio / 1-bed flat, single occupant, single bathroom | Slimline indirect or direct. 0.62 kWh/24h standing loss. ErP Class B. | 20 min reheat (3 kW immersion) |
| Megaflo Eco 125L | 1–2 bed flat, 1–2 occupants, single shower bathroom | Indirect Plus or direct Plus. Floor-standing 1140 mm tall. ErP Class B. | 22 min via boiler (24 kW) |
| Megaflo Eco 145L | 2-bed flat, 2 occupants, shower + basin loadings | Indirect Plus. 0.96 kWh/24h. 1340 mm tall x 545 mm dia. | 25 min via boiler (24 kW) |
| Megaflo Eco 170L | 2–3 bed flat or terrace, 2–3 occupants, single bath | UK bestseller. Indirect Plus. Heatrae Sadia 25-year tank warranty. | 30 min via boiler (28 kW) |
| Megaflo Eco 210L | 3–4 bed terrace, 3–4 occupants, 1–2 bathrooms | Indirect Plus SystemFit option. Duplex stainless steel. | 35 min via boiler (28 kW) |
| Megaflo Eco 250L | 4–5 bed family home, 2 bathrooms, occasional bath fill | Indirect Plus / SolarPlus variants. ErP Class C. | 42 min via boiler (32 kW) |
| Megaflo Eco 300L | 5+ bed home, 3 bathrooms, simultaneous shower demand | Indirect Plus. Requires 1.5 bar minimum dynamic mains pressure. | 50 min via boiler (35 kW) |
Reheat times are full cold-to-60°C with the stated heat source on indirect models. Direct models with twin 3 kW immersions reheat 170L from cold in roughly 2 hours 40 minutes.
Megaflo installation cost London — 2026 prices
Every quote is a fixed figure given after a free on-site survey. No call-out fee on quoted work. No parking add-ons. No out-of-hours premium on scheduled installs. Prices include VAT, the cylinder, full G3 inlet group, expansion vessel, T&P discharge pipework, Benchmark commissioning, Building Regulations notification through the Competent Persons Scheme, removal and disposal of the old cylinder and a 12-month workmanship guarantee.
| Job | What's included | Price |
|---|---|---|
| Megaflo Eco 125L — direct / indirect fitted | Supply & fit cylinder, full G3 inlet group, expansion vessel, T&P discharge to outside, Benchmark logbook, Building Regs notification. | £1,495 from |
| Megaflo Eco 145L — indirect fitted | Like-for-like swap, primary connections to existing boiler, commissioning, demonstration, 12-month workmanship guarantee. | £1,595 from |
| Megaflo Eco 170L — indirect fitted (bestseller) | UK bestseller install. Full inlet group, discharge route, electrical isolator check, Benchmark logbook, Building Control notification. | £1,745 from |
| Megaflo Eco 210L — indirect SystemFit | Pre-plumbed SystemFit variant where space allows. Saves 60–90 minutes on the install. G3 certificate posted within 30 days. | £1,895 from |
| Megaflo Eco 250L — indirect Plus | Larger family install. Inlet group, expansion vessel, discharge to drain or external wall, mains pressure verification. | £2,195 from |
| Megaflo Eco 300L — indirect Plus | Whole-house large install. Includes mains pressure check, secondary circulation tie-in if specified, full G3 paperwork. | £2,595 from |
| Vented → Megaflo conversion (150L) | Loft tank removal, new mains feed, full G3 group, expansion vessel, discharge pipework, electrical isolation, Building Control notification. | £2,495 from |
| Annual Megaflo G3 service | 12-point checklist: vessel pre-charge, T&P lift, PRV outlet, thermostat cut-out, immersion resistance, Benchmark refresh. | £155 fixed |
| Labour-only Megaflo install (customer supplies cylinder) | Engineer-only install where homeowner has sourced cylinder. G3 cert + Benchmark logbook completed and signed. | £695 from |
| Out-of-hours emergency Megaflo callout | Same-day evening / weekend / bank holiday response for leaks, T&P discharge, no hot water, scalding water. | £165 first hour |
* Prices include VAT. Heat-pump-paired Megaflo HeatPump and SolarPlus variants priced separately on survey. Full price list on the pricing page.
Need a fixed price on your Megaflo install?
Call 0207 046 1363Our 5-step Megaflo install process
Every Megaflo install runs through the same five steps in the same order. The reason every step exists is to remove uncertainty on price, timing and compliance before the cylinder leaves the merchant.
Phone consultation & indicative quote
10 minutesCall 0207 046 1363 or WhatsApp 07456 975436 with property type, current cylinder size (if known) and the symptom or reason for replacement. We give an indicative price band on the call and book the free on-site survey, usually within 48 hours.
Free on-site survey
30 minutesG3 engineer attends, measures the cupboard, tests cold mains pressure and flow rate, inspects existing pipework, checks the discharge route options to outside, and confirms whether the airing cupboard, immersion isolator and electrical isolator are usable. You get a fixed written price the same day — usually within 2 hours of the survey.
Booked install date & fixed price
Within 5 working daysMost Megaflo Eco sizes are on next-day order from Heatrae Sadia and stocked in Greater London merchants. Like-for-like swaps usually scheduled within 3–5 working days. Vented → unvented conversions need 5–10 working days for Building Control notification and parts kit assembly.
Install day
4–8 hoursTwo engineers on site for a like-for-like swap (4–6 hours). Isolation, drain-down, old cylinder removal, new Megaflo positioning, primary and secondary pipework, full G3 inlet group, discharge pipework in copper to BS EN 1057, immersion and stat wiring, refill, vent and leak test.
Commissioning & Benchmark handover
60 minutesSystem pressurised, balanced, run-up to 60°C, all four safety devices witness-tested (thermostat, energy cut-out, expansion vessel pre-charge, T&P relief valve). Benchmark logbook completed, signed and stuck inside the cupboard. Building Regulations Compliance Certificate posted to you within 30 days via WaterSafe / BESCA Competent Persons Scheme.
G3 compliance & Benchmark commissioning
A Megaflo install is not just a plumbing job — it is a controlled service under Approved Document G3 of the Building Regulations. Six things must be true for the install to be lawful and the manufacturer warranty to stand.
G3 ticket required by law
Approved Document G3 of the Building Regulations 2010 (as amended) makes installation, commissioning and modification of any unvented hot water vessel over 15 litres a controlled service. Our engineers hold a current G3 certificate (BPEC HWSS or LCL Awards 6189), renewed every 5 years and verifiable on demand.
Building Control notification
Every Megaflo install is notified to building control through our Competent Persons Scheme registration (WaterSafe / BESCA). You receive a Building Regulations Compliance Certificate by post within 30 days — this is what conveyancing solicitors will ask for if you sell.
Benchmark logbook completed on site
Heatrae Sadia's 25-year tank warranty on the Megaflo Eco is conditional on a completed Benchmark commissioning entry plus annual G3 service entries. We complete and sign Benchmark before we leave site and email a scanned copy within 24 hours.
WRAS-approved wetted components
Every part in the inlet group — PRV, check valve, strainer, expansion vessel, T&P valve, tundish — carries WRAS approval under the Water Supply (Water Fittings) Regulations 1999. Non-WRAS parts on a new install are a Water Regulations breach.
Discharge pipework to G3 / BS 6700
Tundish discharge pipework is sized one size larger than the T&P valve inlet (typically 22 mm from 15 mm), with continuous fall, no more than three bends and a maximum equivalent length per Heatrae Sadia's table. Termination is to a visible external location with a 300 mm air gap — never into a soil stack, hopper or internal void.
Electrical work to BS 7671
Immersion heater circuits and cylinder thermostat wiring carried out to the 18th Edition Wiring Regulations (BS 7671:2018+A2:2022). RCD protection confirmed, fused spurs rated to manufacturer spec, earthing and bonding tested. We issue a minor electrical works notification where required.
On commissioning day we run a witnessed test of every safety device, log the cold inlet pressure, the PRV outlet pressure, the expansion vessel pre-charge and the T&P lift, then sign the Benchmark entry inside the cupboard. A scanned copy lands in your inbox within 24 hours; the Building Regulations Compliance Certificate is posted by WaterSafe / BESCA within 30 days. Lose the Benchmark page and the 25-year tank warranty is at risk — keep it stuck to the inside of the cupboard door.
Recent Megaflo installs — London worked examples
Five anonymised London Megaflo jobs from the last twelve months, with the survey findings, the work done and the final figure. Every job was Building Regulations notified, Benchmark logbook completed and 25-year tank warranty preserved.
1990s Gledhill EnviroFoam swap — Megaflo Eco 210L Indirect, Camden
Edwardian conversion flat. Original 1990s Gledhill cylinder leaking from a corroded immersion boss. Survey confirmed dynamic mains 2.4 bar at the inlet, plenty of headroom for unvented. Like-for-like swap to a Megaflo Eco 210L Indirect Plus, full G3 inlet group, new 22 mm discharge through an external wall into a hopper drain, secondary return preserved. One day on site, two engineers. Final invoice: £1,895 inc. VAT — Benchmark and Building Control notification included.
Vented system retirement — 4-bed semi, Wandsworth
1970s open-vented cylinder with cold-water tank in the loft, header tank above. Power-shower upgrade was the trigger — tank-fed flow could not match a thermostatic 12 L/min head. Full conversion to Megaflo Eco 250L Indirect. Loft tank and pipework removed, new 22 mm mains feed pulled to the cylinder, full G3 group, discharge through external wall above a gully, motorised valves re-wired to the new cylinder stat. Two days on site. Final invoice: £3,295 inc. VAT.
Megaflo Eco 170L like-for-like — 2-bed flat, Islington
2008 Megaflo CL Indirect 170L past economic repair — expansion vessel replaced twice, PRV once, T&P once, and the tank was starting to weep at the immersion boss. Swapped for current Megaflo Eco 170L Indirect Plus. Existing primary and secondary pipework re-used, full new G3 inlet group, new discharge through the existing route. 5 hours on site. Final invoice: £1,745 inc. VAT.
300L for a 5-bed townhouse — Kensington & Chelsea
Architect specified a 300L Megaflo Eco Indirect for a 5-bed renovation, 3 bathrooms, freestanding bath in the master. Mains pressure on site 3.2 bar dynamic — well inside spec. Full new installation in a ground-floor utility, primary feed in 28 mm copper from the system boiler, secondary return on a small bronze pump, discharge run 4 m to an external wall above a gully. Two engineers, one day on site. Final invoice: £2,895 inc. VAT.
Mansion-block discharge re-route — Westminster
Inherited Megaflo 145L with the T&P discharge routed into a soil stack inside the cupboard — a clear G3 breach flagged on the buyer's homebuyer survey. New 22 mm copper discharge run from the tundish across the cupboard, through the external wall above the rear lightwell with a visible 300 mm air gap, and a sleeved penetration to BS 8000 standards. Building Control re-notified through the CPS. Half day. Final invoice: £445 inc. VAT.
Ready to book your Megaflo survey?
Free on-site survey within 48 hours. Fixed written price the same day. Like-for-like installs typically completed within 5 working days. Vented-to-unvented conversions within 10 working days. Building Regulations Part G3 notification and Benchmark commissioning included on every install.
Megaflo installation across London
G3 qualified Heatrae Sadia installs across every London borough. Heaviest call volumes from Camden, Westminster, Islington, Hackney, Tower Hamlets, Wandsworth, Kensington & Chelsea and Hammersmith & Fulham.
Megaflo installation — frequently asked questions
What is the Megaflo Eco and why is it the UK bestseller?
How much does Megaflo installation cost in London?
What size Megaflo do I need for my London home?
Is Megaflo better than Telford, Gledhill or Joule?
What is the difference between Megaflo Eco Direct and Indirect?
How long does a Megaflo install take?
Do you need a G3 engineer to install a Megaflo?
What is the Benchmark logbook and why does it matter?
What mains pressure does a Megaflo need?
Where does the T&P discharge pipe go?
Does Megaflo come with a warranty?
Do Megaflos lose pressure over time?
Can I have a Megaflo in a top-floor flat?
Will a new Megaflo save energy compared to my old cylinder?
Do I need an annual service on a Megaflo?
Question not answered? Call 0207 046 1363 and talk to a G3 engineer directly — no call centre, no triage.
Service area
Megaflo installs across all 32 London boroughs
G3 qualified Megaflo specialists based in central London with same-day survey cover across all 32 London boroughs and the City. Average survey turnaround inside Zone 1–3 is under 48 hours.
Megaflo Eco — installed, commissioned and warranted across London
G3 qualified Heatrae Sadia specialists. From £1,495 fitted on the 125L through to £2,595 fitted on the 300L. Free survey within 48 hours. Fixed written price the same day. Building Regulations Part G3 notification, Benchmark logbook and 25-year tank warranty on every install.
London 247 Home Services Ltd · Company No. 17120057 · £5M public liability · G3 qualified · 24/7 emergency line