Megaflo Installation
London
Specialist Megaflo unvented cylinder installation by G3-qualified engineers. Correct cylinder sizing, mains flow assessment and full Building Regulations Part G commissioning.
Upgrading from a vented cylinder?
A Megaflo delivers mains-pressure hot water to every outlet simultaneously — no loft tank, no weak showers.
Book a Megaflo Survey
G3-qualified engineers. Fixed-price quote — no obligation.
Site survey — fixed quote within 24 hours
Megaflo installation in London typically costs £1,500–£3,500 for a like-for-like Megaflo cylinder replacement, and £2,500–£5,000 for a full vented-to-unvented system conversion. RARE's G3-qualified engineers assess incoming mains flow and pressure, size the Megaflo cylinder correctly for your household demand, and commission to Building Regulations Part G. A standard Megaflo replacement takes 3–4 hours; a full system conversion takes a day. Book a site survey for a fixed-price quote.
Megaflo Unvented Cylinder Installation Specialists
RARE Plumbing London specialises in the installation and replacement of Megaflo unvented hot water cylinders across London. Our G3-qualified engineers assess cylinder sizing, incoming mains flow and pressure, boiler output and simultaneous hot-water demand before specifying an installation. Every Megaflo is commissioned and signed off with full Building Regulations Part G documentation.
Megaflo Cylinder Installation
Brand-specialist installation of Megaflo and Heatrae Sadia unvented cylinders, commissioned to full G3 standard.
G3 Qualified Engineers
Every Megaflo installed and signed off by a G3-qualified engineer under Building Regulations Part G.
Megaflo Replacement & Upgrades
Like-for-like replacement of failed or ageing Megaflo cylinders, or full upgrades from vented to unvented systems.
Mains Flow & Pressure Testing
Incoming mains flow and pressure assessed before installation to ensure the Megaflo will perform correctly.
Megaflo for Multiple Bathrooms
Correctly sized Megaflo cylinders for homes with two or more bathrooms and simultaneous hot-water demand.
Cylinder Sizing & Demand
Demand-based sizing to ensure every outlet delivers full mains pressure at once — not a guess.
Megaflo Installation Costs
Clear, upfront pricing — no hidden extras. Fixed quote after survey.
£1,500–£3,500
Like-for-like Megaflo replacement
- Like-for-like Megaflo cylinder replacement
- Removal & disposal of old cylinder
- New expansion vessel, PRV & T&P relief valve
- Full G3 commissioning & Part G documentation
- System flush & pressure testing
- Warranty registration
£2,500–£5,000
Full vented-to-unvented conversion
- Full vented-to-unvented system conversion
- Removal of loft cold water storage tank
- New Megaflo cylinder, expansion vessel & PRV
- All pipework modifications & connections
- G3 commissioning & Building Regs Part G certificate
- Reclaimed loft space
Heating & Hot Water System Design
A hot water cylinder is part of a system — not a standalone appliance. Before recommending a cylinder, RARE engineers assess the whole property to ensure the cylinder, boiler and pipework work together correctly. We size for your actual demand, not a guess. Most installers replace the equipment and leave. RARE designs the installation around your property.
Property & Demand
- Property size and layout
- Heat requirement (kW)
- Number of bedrooms
- Number of bathrooms
- Number of occupants
- Expected simultaneous hot-water usage
Water System
- Incoming mains pressure
- Incoming mains flow rate
- Existing pipe sizes
- Existing cylinder type & condition
- Direct vs indirect configuration
- Recovery times and boiler output
Heating System
- Existing boiler make, model & output
- Heating zones
- Underfloor heating integration
- Radiator sizing and layout
- Smart controls & weather compensation
- System balancing requirements
Practical Considerations
- Plant-room / cupboard space
- Flue route and condensate arrangements
- Future maintenance accessibility
- Water quality and hardness
- Building regulations compliance
- Warranty registration
System Boiler + Unvented Cylinder — designed together
Many premium London properties — townhouses, mansion flats and homes with multiple bathrooms — need a properly designed combination of a system boiler and an unvented hot water cylinder. The boiler heats the home and re-heats the cylinder; the cylinder stores hot water at mains pressure for simultaneous showers and baths. Getting this combination right means sizing both components together based on actual demand, not installing them in isolation.
Combi Boiler Alone
Heats water on demand without a cylinder. Compact and efficient — ideal for flats and homes with 1–2 bathrooms where simultaneous hot water use is limited.
- No cylinder needed
- Compact footprint
- Best for 1–2 bathrooms
- Limited simultaneous hot water
System Boiler + Cylinder
The boiler heats radiators and re-heats the cylinder. The cylinder stores hot water at mains pressure — delivering simultaneous hot water to every bathroom. The right solution for homes with 2+ bathrooms.
- Full mains pressure at every outlet
- Simultaneous showers and baths
- Ideal for 2+ bathrooms
- Boiler and cylinder sized together
Cylinder Upgrade
Replacing a vented cylinder with an unvented Megaflo or OSO delivers mains-pressure hot water without changing the boiler. Effective when the existing boiler is still serviceable.
- Mains pressure without new boiler
- Removes loft cold water tank
- Faster hot water recovery
- Boiler must have adequate output
Need a new boiler too? See our Boiler Installation & Replacement page
RARE sizes the boiler and cylinder together to ensure reliable heating and hot water for the whole property.
Megaflo Installation Questions
Common questions about Megaflo installation in London.
Still have questions?Serving London's most iconic neighbourhoods.
Our engineers are established across prime London — near landmarks including Berkeley Square, Harrods, Eaton Square, Regent's Park and Hampstead Heath.
Megaflo installation — related guides
Hot Water Cylinder Installation
Full unvented cylinder installation service
Megaflo Servicing
G3-qualified annual service
Megaflo Repairs
Megaflo fault diagnosis & repair
System Boiler Installation
For larger homes with cylinders
Plant Room Installation
Bespoke plant room design
Boiler Installation Costs
Full London pricing guide
Boiler Replacement Guide
Repair vs replace explained
What is a Megaflo?
Unvented cylinders explained
Megaflo vs OSO
Cylinder comparison
PPM Membership
Annual servicing & priority response
Water Softener Installation
Protect your Megaflo from limescale
Hard Water & London Heating
Scale, inhibitors & softener integration
Reviewed by RARE Plumbing London Engineering Team
Gas Safe Registered Heating Engineers · Reviewed 3 September 2026