Hot Water Cylinder Specification - How Things Have Changed

Hot Water Cylinder Specification

Times have moved on dramatically from the traditional approach to domestic hot water systems, with a vented cylinder fed by a tank in the attic, heated by solid fuel or an immersion heater.

The increase in hot water demand, developments in technology, combined with rising energy prices and a growing pressure to reduce the carbon footprint, has seen the range of hot water cylinders on the market explode.

The rapid growth of technology, together with European directives and government incentives has fuelled the renewable energy market with a plethora of sources now being used, such as solar thermal, heat pumps, wind technology, as well as reverting back to traditional solid fuels.

This has potentially had the most significant impact on hot water systems and cylinder design with the increase in multi-fuel cylinders rising dramatically.  Our THERMflow thermal store can take a wide range of heat inputs and provides excellent mains pressure at hot taps.  

There is also a focus on the energy efficiency of hot water cylinders with architects, specifiers and end clients paying closer attention to reheat times and heat loss.  This has led to products such as our copper POWERflow Unvented Cylinders with high efficiency copper coils for solar and heat pump input.  Coil material and surface area play a critical part of optimising the renewable heat source.  If there is not enough coil surface area and it is made from material other than copper then these units can be more expensive to run rather than saving householders money.

Insulation has also increased from the original un-lagged cylinders to now generally having 50mm Insulation.  We also regularly insulate cylinders with 100mm to reduce heat loss even further.  

Copper versus Stainless Steel

The vast majority of cylinders were manufactured from copper, but because of market price volatility, copper became very expensive, though it has fallen steadily since.  This led to the alternative of Stainless Steel as a cheaper material for manufacture. However demand for energy efficiency has also sparked a real debate over the performance attributes of copper and stainless steel, with the University of Ulster carrying out a research project to compare the materials when used for water storage.

Their findings showed that with similar coil surface area, copper hot water cylinders heated the water 28.8% faster than stainless steel.

When they took a standard off the shelf copper cylinder and compared it with the same in stainless steel, the copper cylinder showed a 62.6% increase in the power output and average effectiveness.

Our Vented cylinders still use 28mm copper coils and not only does this provide excellent re-heat times, but can also be used on Gravity circulation as well as pumped.

Copper’s unrivalled bacteria killing properties, which kills most bacteria including Legionella, MRSA and Ecoli, has also made it the preferred choice for many commercial installations.  Our copper Calorifiers help systems provide healthy and safe hot water, particularly important, as the issue of health and safety has never been greater

Changing Demographics

Changing demographics is also changing the hot water cylinder market. With people living longer, we have seen a rise in social housing to accommodate single person living in sheltered type housing. 

This has seen a growth in demand for smaller cylinders with 70-100 litres capacity as well as combined hot water packages, such as our CENTRALflow hot water storage system, which uses a combination of thermal stores and heat interface units working with a central boiler system.  The flexibility of manufacture that we have, means there is generally a product that will fit the space and customer requirements exactly.

The Impact of the Construction Industry

The last 20 years has witnessed the biggest ever boom and bust in the construction industry with house building reaching unprecedented highs before an equally sharp decline.

This changed the face of the entire industry with competition becoming increasingly fierce, lead times shortening and focus on value engineering.

And whilst there has always been a degree of specification busting, many contractors are focusing on value engineering and looking at how they can optimise the cylinder design, such as repositioning the connections, to reduce installation costs. 

One of the major changes has been the issue of space utilisation as designers look to minimise the floor space taken by services such as the hot water cylinder. This is resulting in a growth in demand for our Slimline cylinders and our CUBEflow rectangular tanks which can actually deliver the same capacity in 27% less space. 

There is generally a product to suit the installation and we have an excellent technical team to help and advise.  Call 01592 611123 or email