Jon Cockburn, head of marketing at Heatrae Sadia, warns that buying a low-cost unvented hot-water system could see you get your fingers burned once those frequent maintenance bills start rolling in
When commercial premises need powerful, high-performance hot water for washrooms and stand-alone sinks and basins, small unvented water-heating products offer an ideal solution.
Fed directly from the cold water mains, unvented systems provide powerful hot water without a loss of performance if more than one tap is used at the same time.

This kind of system is usually installed in homes where large unvented cylinders are used to serve multiple bathrooms.
Lower-capacity versions can
satisfy the hot-water requirements of washrooms in commercial and public-sector premises.
As well as delivering powerful hot water, small unvented water heating units can be more cost effective to install than a single sink open-outlet heater.


This works well where there is a need to supply a number of sinks. And, in larger buildings, the
provision of a number of small unvented water heaters can
provide a more flexible design
solution. Unvented hot water storage units can also include thermostatic blending valves, which allow water to be stored at a high enough temperature to eliminate bacteria, yet dispense it at a safe, pre-set, hand-wash temperature.
This is ideal for applications where temperature control is a vital requirement, for example in schools, nurseries, care homes,
hospitals and hotels.


Alongside these benefits, small unvented hot-water systems are becoming more popular because of changing attitudes. Our
knowledge about hygiene and bacteria has increased significantly in recent years. This has led to a much higher demand for effective
hand-washing facilities.


We all now appreciate that there should be adequate hand-washing
facilities in commercial and public-sector premises, especially where hygiene is a priority.


The growth of hospital
superbugs such as MRSA - and the suggestion that frequent, thorough hand washing could prevent them from spreading - has
highlighted how important the provision of effective hot water is.


Secondly, people's expectations about hot-water provision within public-sector and commercial premises have changed.
For example, some years ago it would have been commonplace, and acceptable, to find restaurant washrooms with just a cold-water tap for hand washing.
People going to expensive restaurants and bars now have higher expectations.


As a result, we have seen many more manufacturers entering the small unvented market - mirroring what has happened in the large unvented sector. I admit that when a specifier or installer is
costing for a low-cost small unvented unit - with promises of powerful hot-water delivery - it could seem attractive.
But these lower-cost options are usually made from inferior
materials. This could, in turn, lead to service and maintenance issues.


Because unvented systems store water under pressure, the material that the inner container is made of is very important.
Using high-grade materials in the manufacture of small unvented water heaters significantly reduces maintenance requirements.
These units will undoubtedly be at the top end of the price range - but, as with all things in life, you get what you pay for.
There are many low-cost small unvented units available, but these are usually manufactured from mild steel or low-grade copper.
Small unvented units manufactured from mild steel require a coating or glass lining and an anode to make them corrosion resistant. Some low-grade copper units also require an anode.
The anode will need to be inspected for signs of erosion every six to 12 months.


Installers should also be aware that mild-steel glass-lined products are also around 50% heavier than an equivalent stainless-steel unit.


These are therefore more difficult to manoeuvre and install.
Heatrae Sadia manufactures a range of small unvented systems suitable for commercial applications - all with high-grade copper inner containers.


Unvented water-heating storage is becoming the norm in the domestic market, but the benefits are now filtering through to the commercial sector.
However, specifiers and installers should be wary about low-cost products.
Lifecycle costs can be a more important consideration than the initial purchase price.