Why water composition matters when selecting commercial water heaters

When specifying a commercial water heater, there are several performance factors to consider such as efficiency, capacity, and compliance. But one often overlooked consideration is the composition of the water itself. Local water quality can have a significant impact on the performance, maintenance needs, and lifespan of a hot water system.

The difference between hard water and soft water

Water composition refers to the presence of minerals, pH balance, and any particles or impurities within the water supply. These factors vary from region to region and can affect how a water heater performs over time. Ignoring these differences can lead to unexpected inefficiencies, system damage, or increased operating costs.

• Hard water

Hard water is one of the most common water quality challenges across the UK. It contains elevated levels of calcium and magnesium, which precipitate out under heat as insoluble calcium carbonate (CACO3) deposits, which then attaches inside the tank and around heating components, and form scale inside the tank and around heating components. As this layer of scale builds, it creates an insulating barrier between the water and the heat source, reducing efficiency and forcing the system to work harder. This not only leads to longer recovery times and higher energy use but also increases wear on components, ultimately shortening the lifespan of the water heater. For commercial buildings where hot water demand is constant, hard water can quickly lead to reduced system performance and rising operational costs if not properly addressed. In these cases, either a water treatment strategy or selecting a unit designed to withstand mineral build-up is essential to ensure longevity and reliability.

• Soft water

Soft water contains fewer dissolved minerals than hard water, making it more acidic and lowering its pH, as these minerals typically act as natural buffers. This acidity can accelerate corrosion of internal components of water heaters. Corrosive water can degrade metal surfaces, particularly in systems made from materials with less resistance to acidic conditions. This kind of degradation can often leads to leaks, joint failure, and a general decline in system integrity.

While the issue of corrosion is most closely associated with soft water supplies, scale usually forms in the hottest areas of a water heater. The material underneath a scale deposit is an acidic and aggressive environment which means that corrosion and eventual breakdown is inevitable. Using water heaters with corrosion-resistant materials, such as stainless steel can offer added durability in such conditions - once corrosion is allowed to begin to occur then there is no stopping or reversing it.

• Sediment and particulates

Even where water isn’t particularly hard, sediment can still present challenges. Sediment typically consists of small particles that enter the system through the water supply or form as a result of pipe corrosion. These particles settle at the bottom of the tank over time, particularly in storage systems. This buildup can reduce heating efficiency, increase the risk of overheating, and potentially cause damage to the tank. The effects of sediment are often gradual, and because they aren’t always visible, the problem may go unnoticed until performance drops or the tank begins to fail. Regular maintenance, including flushing the tank and appropriate filtration, is important to maintain system efficiency and increase the lifespan of water heaters.

Why water composition matters for commercial installations

Understanding the characteristics of the local water supply is critical when selecting a commercial water heater, especially where there is a high demand for constant hot water. If the material isn’t suited to local water conditions it can lead to premature failures, costly maintenance, and energy inefficiencies. By selecting a heater designed to handle specific water characteristics, commercial properties can ensure reliable performance, reduce the risk of unplanned downtime, and extend system lifespan.

Enhanced durability with the DR-SG water heater

Built to handle tough water conditions, the Dorchester DR-SG comes with a stainless steel tank, coil, and heat exchanger, plus a protected anode for added durability and corrosion resistance so you can rely on it to maintain performance, especially in areas with soft water corrosion. Its compact, lightweight design makes transport and installation easy, while still delivering the high flow rates needed for high demand large commercial buildings. With ErP Class A efficiency and full NOx compliance, it delivers reliable performance with reduced environmental impact.

Whether you're working on a new build or replacing an existing system, the Dorchester DR-SG is well suited to the demands of schools, hospitals, hotels, and other high-use environments where hot water supply must be consistent and resilient, even under challenging water conditions.

For more information on the Dorchester DR-SG and its impact, see how it provided a reliable and efficient hot water solution for The Knaresborough Inn by reading the case study here.

Navigate the selection process with Hamworthy Heating

Understanding the composition of your water is essential when selecting the right commercial water heater. With varying levels of hardness, acidity, and sediment across the UK, choosing a system that can withstand these conditions helps ensure long-term performance, energy efficiency, and reliability, especially in demanding commercial environments.

Hamworthy Heating works with commercial consultants and specifiers to help them find the right solution for their energy-efficient and low carbon water heating solutions for their commercial projects. Whether that’s support with technical information, or choosing the best water heater for your project, the Hamworthy Heating specification team can help at every stage of the specification process.

For more information on how water composition could affect your system design, get in touch with your Area Sales Manager.