Best hot water cylinder UK

Best hot water cylinders – vented and unvented hot water cylinders

megaflo hot water cylinders

Hot water cylinders are used in conjunction with system boilers or regular boilers. They store hot water that has been heated by the boiler ready for use on your hot water tap when you need it.

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These are the types of boilers that when people say, don’t use all the hot water, that people have in their homes. If you have a combi boiler, you will not have a hot water cylinder or a cold water storage tank.

Let’s take a look at the different types of hot water cylinders and how they work.

Once we have had a look at each hot water tank, we will review the best ones available on the market right now to use with your heating system.

Unvented hot water cylinders

These hot water tanks are mains-fed hot water cylinders that have an inner coil, but no open vent pipe. An expansion vessel is used to allow heated water to expand.

In order to withstand increased pressure, unvented hot water cylinders are made of steel and not copper. The unvented hot water cylinders are equipped with many safety devices that must be installed and maintained by qualified engineers.

tempest hot water cylinders

An unvented hot water cylinder can be installed alongside a system boiler or regular boiler. This is great for homes with multiple bathrooms. The best unvented hot water cylinder along with a condensing boiler will lower your heating bills, provide strong water pressure, and meet your demand.

Professional installers recommend unvented cylinders over traditional vented systems. You can also use electric immersion heaters with a hot water cylinder too to heat water if required.


  • They can provide excellent hot water flow rates to multiple showers when the mains pressure is low
  • You can also have greater flexibility when placing the unit. They don’t have to be placed at a high point of the system.
  • There are ‘Rapid Recovery’ models that allow for quick re-heat times.
  • Can be used with solar panels


  • These are more costly to install along with new boiler costs
  • They must be installed by an engineer qualified to maintain them
  • Long-term maintenance costs are higher for other components

Hot water cylinders with open vents

Copper cylinders with open venting work well in combination with a cold storage tank. The open vent pipe extends from the top of the copper hot water cylinder and rises to the top of the cold water storage tank before hooking over to it.

In the event of an extreme heat fault, the open vent pipe lets out excess pressure and heat from hot water systems.

vented hot water cylinder

They do not depend on the mains pressure to provide hot water at a high flow rate. If mains pressure is low, they can be retained.

A central heating pump can further improve the performance of an unvented hot water cylinder. NB: It is possible to have an open-vented hot water system, even if your heating system is sealed.


  • They can provide high hot water flow rates even when the mains pressure is low.
  • A pump can improve flow rates
  • A Copper unvented hot water cylinder can be replaced at a very affordable price
  • Can be used with solar panels


  • Copper tanks that have been left uninsulated are inefficient.
  • Unvented hot water cylinder takes up a lot of space
  • They should be located at an elevated point of the central heating system

What are the best unvented hot water cylinders?

Your home’s hot water demand will determine the best unvented cylinder. There are many options available when searching for the best unvented hot water cylinders and all come with great long warranties

These are some of the top unvented cylinder leading manufacturers

  • Heatrae Sadia
  • Telford
  • Gledhill
  • Viessmann
  • Vaillant

Heatrae Sadia Megaflo hot water cylinders

Heatrae Sadia makes the Megaflo eco Plus, one of the most popular unvented hot water cylinders currently on the market. These unvented cylinders are covered by a lifetime warranty and have a high flow rate. They also offer excellent heat retention and energy efficiency.

Heatrae Sadia’s reputation has been impressive over the years. The Megaflo Eco Plus should be considered the best-unvented hot water cylinder you can buy in 2022. These cylinders are slightly more expensive than the others mentioned in this article but it is a fair price for a quality product that will not let you down.

Megaflo hot water cylinder

Megaflo Eco Plus features a floating baffle expansion vessel inside the unit, so that there are no additional sections to accommodate. These are the key features:

megaflo unvented hot water cylinder
  • Capacity ranges from 250 to 1000 litres
  • High flow rates up to 176 Liters per Minute
  • A heating coil or heating elements are electric to provide a rapid heat recovery time.
  • External expansion vessel is required on an unvented hot water cylinder
  • SystemReady and SystemFit pre-plumbed options for heat-only and system boilers
  • 60mm CFC/HCFC-free injected foam provides heat retention and energy efficiency.
  • The unique ‘L-shaped’ immersion heater maximizes hot water volume

Megaflo Eco Plus Cylinders come with a lifetime guarantee. This makes them one of the most reliable unvented cylinders.

Viessmann hot water cylinders

vitocell hot water cylinder

The Viessmann Vitocell 200V is a series of unvented, indirectly heated cylinders that can be installed alongside a Viessmann Vitodens 100-w system boiler. It can also be used with traditional S or Y plan heating systems or non-Viessmann boilers or heating system if an additional safety kit is purchased.

  • Capacity up to 300 litres
  • 50mm polyurethane foam insulation surpasses CHESS Best Practice with energy losses as low as 1.4kW/24 hr
  • The heating coil can be recovered in under 19 minutes, providing a water reheat time of 30 minutes from cold.
  • Included is a backup immersion heater (3 kW).
  • Included with an external expansion vessel
  • Simpler installation thanks to lightweight design

Viessmann has added a 25-year warranty against corrosion to its Vitocell 200V hot water tank.

Vaillant hot water cylinders

Vaillant is another brand that is well-known in the boiler market. The UniSTOR unvented hot water cylinder comes with a 2-year warranty on parts and labor, and a 25-year warranty for cylinder shells.

vaillant hot water cylinders

These units are available in standard, slimline, and pre-plumbed styles. They also have improved insulation, which reduces heat loss and makes them more cost-effective and energy-efficient. For ease of boiler installation, they can be attached to existing heating systems.

Vaillant uniSTOR unvented hot water cylinders are available in Slimline, Pre-Plumbed, and Standard models. Each model comes with a variety of features such as:

  • Standard cylinders 120l and 150l have an ErP-A-rating
  • For installation on uneven surfaces, adjustable feet are possible
  • To reduce heat loss, the house is fitted with high insulation

You get a 2 year parts warranty and a 25-year guarantee on the cylinder shell.

Telford hot water cylinders

Telford produces some amazing unvented hot water cylinders. The most famous of these is the Telford Tempest. This unvented cylindrical is made of stainless steel, which makes it up to 40% thicker that other unvented ones on the market.

tempest hot water cyldiners

Domestic Telford cylinders can hold up to 500 litres of water for direct and indirect cylinders. You can choose from pre-plumbed, slimline, or horizontal models to meet your needs.

The Telford Tempest Indirect Unvented Cylinder has been created for use in heating systems that include a gas or oil boiler. The Telford Tempest Indirect Unvented Cylinders have the following key features:

  • Duplex stainless steel offers high resistance against corrosion
  • To retain heat, the entire house is fully insulated
  • A 3kW immersion heater
  • There are a variety of capacities available, from 90 liters to 500 litres

The 2 year warranty covers the components, while the lifetime warranty covers the inner container.

Gledhill hot water cylinders

Gledhill’s Platinum Range, a brand new line of unvented cylinders, offers many exciting features that are hard to beat. They are easy to install and come with a 25-year warranty.

They are extremely well insulated to reduce heat loss and make them an industry leader in energy efficiency. They have a lower capacity than their competition, with a maximum of 300 litres in indirect cylinders and 210 for direct hot water cylinders.

gledhill hot water cylinder

The Gledhill Platinum Range cylinders, like the Telford Tempest are made of tough and durable stainless.

Gledhill’s Stainless Lite Plus Indirect is a highly efficient, unvented cylinder available in a variety of capacities to fit different property types.

The Stainless Lite Plus cylinder has the lowest weight on the market. The high-efficiency corrugated tube coil delivers faster recovery times than ordinary tube coils. It is well insulated to reduce heat recovery time and has a variety of other features:

  • The corrugated coil heats the water efficiently and effectively.
  • Available in capacities ranging from 90 to 400 L
  • Installation time can be reduced due to a 90deg elbow and its low weight.
  • Solar thermal and solar PV are compatible to increase your energy efficiency.
  • To save space, there are also slimline models.

To ensure that you are fully covered, the warranty covers 25 years.

Best unvented cylinders in the UK and which to choose?

There are many new unvented cylinders on the market that offer long warranties and have new features. If you are looking for an unvented cylinder that will last a lifetime, we have listed five of the best models.

Viessmann is up there and they are renowned for their reliability and extra-long corrosion warranty. The Gledhill Platinum Range is the most impressive of the models, but Heatrae Sadia Megaflo has a reputation for quality that will ensure you are not disappointed.

If you don’t like the sound of a hot water tank, then check out some of the best combi boilers on the market right now that means that you do not require an unvented hot water cylinder or an external expansion unit at all.

40kw combi boilers have a much better energy efficiency than a system gas boiler in most cases as they do not constantly have to heat hot water up all day long but can still provide hot water to two taps at the same time.

Find the latest new boiler prices at right now and you can get a system boiler or conventional boiler installed in under 24 hours!

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