The Future of Domestic Hot Water - Unvented Cylinders Are Here

Unvented hot water systems are finally growing in popularity in the UK, which is still mostly reliant on gravity fed systems throughout the housing stock. This system which has its roots in the nineteenth century, suffers from low pressure of hot water (especially in the top floors), and limited availability of hot water to more than one user. It is common for one user to have a shower, only to be surprised by a splash of cold water as soon as another household member turns on the hot water tap elsewhere in the house. Compare this with a steady pressure (equal to the mains pressure of the cold water) all around the house even if more than one tap is used at any point in time.

Hectic lifestyles mean high demand from the basic systems in the home. These days we do not expect to wait for hot water, nor do we expect to get hit by a cold flush of water in the shower when someone else turns on the hot water tap in the house. Furthermore, many modern houses have two bathrooms, as well as a host of other appliances that put pressure on the hot water systems, such as a whirlpool bath or a jet shower. Only unvented systems can offer the reliable supply of hot water in the right quantity and pressure to allow for all this to work seamlessly.

Most unvented cylinders are manufactured from metals that fall into one of three categories: copper, stainless steel and glazed sheet metal. Each one of these technologies is highly effective and used throughout the world.

* Copper shell - the price of copper cylinders has risen recently along with the cost of copper in the world commodity markets. Copper shells are very popular in the UK, offering lightweight and relatively reasonable prices. They offer the lowest level of heat retention among the three metals.

* Stainless steel cylinders - provide middle ground in terms of heat retention and weight, compared to copper and sheet metal. They are the most expensive type, but offer the longest lifetime guarantee (normally around 20-25 years).

* Sheet metal shell - offers the best heat retention properties, and is cheapest of the three technologies. Although heaviest of the three, sheet metal shells are highly popular in the rest of Europe and normally come with an inner enamel glazing, thus reducing build up of scale.

When making your selection of the unvented hot water cylinder, there are several important points to pay attention to:

* Volume and external dimensions - a typical household (4-5 people) in the UK will require a 200 liter cylinder. However, the cylinders come in different shapes and dimensions. Make sure to check the width and height of the cylinder, so that it fits in the airing cupboard (or any other space you plan to position the tank in).

* Heat retention performance - since the main purpose of a hot water tank is to retain the water inside hot, it is important to check the heat loss score of the tank. A good tank loses less than 3 kW per 24 hours).

* Manufacturers service and warranty - although unvented tanks have good record of reliability (they have virtually no moving parts), it is important to note what warranty and service level is provided by the manufacturer.