🔧 What Are Unvented Cylinders? Guide for London Homes
Looking to upgrade your home’s hot water system or better understand your existing setup? Unvented cylinders are a popular, high-performance solution for properties across London — especially those with high hot water demand or multiple bathrooms.
In this blog, we’ll explain how unvented cylinders work, their pros and cons, how to maintain them, and why homeowners often choose premium brands like Megaflo, OSO, Heatrae Sadia, and Santon. Whether you live in a townhouse in Camden or a family home in Hampstead, this guide will help you make a more informed decision.
💧 What is an Unvented Cylinder?
Unvented cylinders store hot water at mains pressure, delivering strong flow to taps and showers without the need for a cold water tank in the loft. They are ideal for modern homes and flats across London where space is limited and strong water pressure is preferred.
Unlike vented systems, unvented cylinders don’t rely on gravity — instead, they take water directly from the mains and heat it using a boiler or an electric immersion heater.
🛠️ How Do Unvented Cylinders Work?
Cold water from the mains enters the cylinder and is heated either:
- Indirectly via a boiler (gas, oil, or renewable energy),
- Or directly using electric immersion elements.
Once heated, the water is stored under pressure and ready for immediate use. The system includes safety features like pressure relief valves, expansion vessels, and thermostatic controls to keep it operating efficiently and safely.
🔍 Popular Brands of Unvented Cylinders
At RARE Plumbing London, we install and maintain all leading brands, including:
- Megaflo (Heatrae Sadia) – One of the most recognised premium brands in the UK for unvented cylinders. Known for robust build quality and consistent water pressure.
- OSO – Scandinavian engineering with excellent energy efficiency ratings and long warranties.
- Santon – A trusted British manufacturer known for compact and high-performance electric cylinders.
- Heatrae Sadia – The parent brand behind Megaflo, also offers a range of direct and indirect unvented solutions for various property types.
These systems are ideal for homes with multiple bathrooms, high water usage, or where space-saving installations are a must.
✅ Benefits of Unvented Cylinders
- Mains Pressure Hot Water – Strong flow at all outlets, perfect for power showers or filling a bath quickly.
- No Cold Water Tank Needed – More loft space and easier installation in modern homes.
- Fast Hot Water Recovery – Especially when paired with a high-efficiency boiler or electric immersion.
- Safe and Reliable – Built-in safety controls and pressure regulation.
- Compatible with Renewable Heating – Works well with solar thermal and heat pump systems when correctly configured.
⚠️ Potential Drawbacks
- Requires High Mains Pressure – May need a booster if your home suffers from low water pressure.
- Professional Installation Only – Due to pressure and safety requirements, must be installed and serviced by qualified engineers.
- Regular Maintenance Needed – Annual service is recommended to check safety valves, expansion vessel pressure, and heating elements.
🧰 Tips for Maintaining Your Unvented Cylinder
Regular maintenance helps avoid emergency breakdowns and extends the life of your system. Our top tips:
- Schedule annual servicing to test safety controls and system pressure.
- Bleed the system if you notice inconsistent temperatures or noisy operation.
- Monitor for signs of pressure loss or temperature fluctuations.
- Ensure your engineer checks the pressure relief valve, expansion vessel, and immersion heater if fitted.
- Stick with genuine parts from brands like Megaflo, OSO, or Santon for repairs.
We offer tailored Planned Preventative Maintenance (PPM) for landlords, developers, and homeowners looking to keep their heating and plumbing systems in top shape year-round.
🔁 Related Services
- Megaflo Services & Repairs in London
- Gledhill Pulsacoil Repairs
- Plumbing Repairs London
- Hot Water Cylinder Repairs & Installation
- Boiler Repairs London
🔐 Why Choose RARE Plumbing London?
- Fully qualified and Gas Safe registered engineers
- Decades of experience working across London postcodes
- Trusted with high-end domestic and commercial systems
- Honest advice on when to repair, upgrade, or replace
- Available for 24/7 emergency callouts
📞 Book Your Unvented Cylinder Service Today
Whether you need help with your existing unvented system or are considering a new installation, RARE Plumbing London is here to help. We install, repair, and maintain Megaflo, OSO, Santon, Heatrae Sadia, and other top brands.
📍 Serving homes across Central and North London
