Unvented hot water storage is becoming increasingly popular for domestic, commercial and public sector properties in the UK. This means a large number of unvented products have entered the market and there’s more choice than ever before. However, according to Heatrae Sadia the manufacturer of Megaflo HE, installers and specifiers should exercise caution when selecting cylinder brands. Here marketing manager David Webster explains why decisions should be based on factors other than cost – for example the material the cylinder is made from, the hot water performance, the length, terms and conditions of the guarantee and the quality of the support package offered by the manufacturer
THE unvented hot water cylinder market has been growing by around 15% per annum since the year 2000, according to figures issued by MODUS (The Association of Manufacturers of Domestic Unvented Systems). Unvented systems are fast becoming the preferred choice for new build homes and bathroom refurbishment projects but their popularity isn't just restricted to domestic dwellings.

Consider commercial and public sector premises with a significant number of showers, baths, basins and sinks in use: hotels; sports and leisure centres; hospitals; care and nursing homes; prisons and large offices, for example. They all have a requirement for powerful hot water and a large unvented cylinder - or several installed in parallel - is the ideal solution.

The growing demand for unvented hot water systems for domestic, commercial and public sector premises means we have seen many more water heating manufacturers entering the unvented market during the past few years - so there's a wide range of products on offer.

So, how do installers and specifiers choose between one cylinder and another? The concern is that this choice all too often comes down to cost. After all, when the price of an unvented system is being calculated, opting for a low- cost cylinder must seem attractive. However, in the long term it may prove to be a false economy.

It is important the installer or specifier, as well as the end user, understand what he is getting for his money. Unvented cylinders are not all the same. They differ in terms of the material they are made from, their hot water performance, the length, terms and conditions of the guarantee and the quality of the support package offered by the manufacturer.

One of the most important things to consider is the material the cylinder is made from. Since unvented cylinders store water under pressure, it is vital they are strong, durable and corrosion- resistant. In the UK cylinders are generally made from stainless steel, copper or glass-lined mild steel but, without a doubt, high-grade stainless steel is the preferred material, following a pioneering lead set by Heatrae Sadia more than a decade ago.

High-grade stainless steel has outstanding corrosion-resistant properties and, being lightweight yet strong. gives a strength-to-weight ratio advantage. Using high-grade stainless steel in the manufacture of unvented cylinders significantly reduces maintenance requirements and costs, and eliminates the need for a protective coating and sacrificial anode.

Cylinders manufactured from mild steel require a coating or glass lining and an anode to make them corrosion resistant. Some lower-grade stainless steels also require an anode. The anode will need to be inspected for signs of erosion each year and replaced if necessary.

Mild steel or low grade stainless steel cylinders might initially seem more attractive because they cost less than those manufactured from high grade stainless steel. However, installers and specifiers should be wary - these less expensive products will require ongoing service, regular maintenance and possible replacement after a relatively short life. Mild steel glass-lined cylinders are also around 50% heavier than an equivalent stainless steel unit, and are therefore more difficult to manoeuvre and install.

Cylinder performance is another area to consider carefully. When choosing an unvented cylinder, hot water flow rates, recovery rates, the amount of stored hot water available and standing heat losses should all be properly researched and assessed. The buyer should check manufacturers' literature and listen to recommendations. After all, an unvented cylinder should promise to deliver powerful hot water and provide fast recovery - and customers will only be disappointed if the system doesn't perform to these expectations.

Guarantees are another area to consider. Even if it is lengthy - for example 25 years - installers and specifiers should check the terms and conditions carefully. For example: does the guarantee cover on-site parts and labour? Can it be transferred if the dwelling or premises are sold?

Finally, the level of support on offer from the manufacturer should be assessed. Is nationwide technical and service support provided? Does the manufacturer offer advice, assistance and product guidance? Is unvented training available through the organisation?

Of course, cost plays an important part in the specification process but it is important for installers, heating engineers, designers and specifiers to remember that choosing a quality, fit-and-forget, high grade stainless steel unvented water cylinder, with a lengthy and comprehensive guarantee and good manufacturer support, makes sound economic sense. It will also ensure the customer is satisfied and expectations are met.