Cold water storage tanks, commonly found in the lofts of residential homes across the UK, have long played a vital role in traditional gravity-fed plumbing systems.
While they serve an important purpose, storing and supplying cold water to feed hot water cylinders and, in most cases, bathroom cold water outlets, their presence in the home also introduces potential health risks, particularly when they are poorly maintained or improperly installed. For homeowners and landlords alike, understanding these risks is essential to ensuring a safe and hygienic water supply.
What are the main concerns with a loft-cased cold water storage tank?
One of the primary concerns with loft-based cold water storage tanks is contamination. Unlike mains fed unvented systems, where water is delivered directly from the mains supply under controlled conditions, water in a storage tank can sit stagnant for extended periods. If the tank is not properly covered or sealed, it becomes vulnerable to the ingress of dust, debris, insulation fibres, and even insects or small animals. Cases of birds or rodents entering uncovered tanks are relatively common, and the resulting contamination can pose serious health risks if that water is subsequently used for washing or brushing your teeth.
Another significant risk is the growth of harmful bacteria, most notably Legionella. This bacterium thrives in stagnant water at temperatures between 20°C and 45°C, conditions that can easily occur in a poorly insulated, incorrectly installed or poorly maintained loft tanks. Inhalation of contaminated water droplets, such as those produced by showers, can lead to Legionnaires’ disease, a potentially severe form of pneumonia. While the risk in a typical domestic setting is lower than in commercial systems, poorly maintained tanks can still create an environment conducive to bacterial growth.
The structural condition and cleanliness of the tank itself are also critical factors. Older tanks, especially those made from galvanised steel, can corrode over time, leading to rust particles entering the water supply. Even modern plastic tanks can degrade or develop biofilm if not periodically inspected and cleaned. Sediment build-up at the base of the tank comprising of limescale, dirt, and organic matter, this can further compromise water quality and provide a breeding ground for microorganisms.
In addition to internal contamination, external environmental factors in loft spaces can exacerbate risks. Loft areas are often subject to temperature extremes, which can affect water quality and system performance. In winter, insufficient insulation can lead to freezing of both unprotected pipework and even the tank itself, while in summer, elevated temperatures can accelerate bacterial growth. Proper lagging of both the tank and associated pipework is therefore essential, not only for system efficiency but also for maintaining safe water conditions.
Do I need to maintain my Cold Water Storage Tank?
Preventative maintenance is the most effective way to mitigate these risks. At a minimum, cold water storage tanks should be fitted with a tight-fitting lid that is intact and secure, preventing any ingress of contaminants. The tank should also include appropriate screening on both overflow and vent pipes to stop insects or vermin from entering. Regular inspections ideally annually along with your boiler and hot water cylinder should be carried out to check for signs of damage, contamination, or sediment build-up. Where issues are identified, professional cleaning and disinfection will be required.
In some cases should your central heating system become faulty it is possible for your cold water storage tank to be filled with very hot water from the heating system (pumping over) should your tank be made of plastic or be incorrectly supported then the outcome could indeed be very damaging to your property, there have also been cases where this has sadly proved fatal.
For many homeowners, upgrading or modifying the system is worth considering. It is possible to remove the need for a loft tank altogether by converting to a mains fed unvented system hot water system, thereby eliminating the above mentioned risks. Alternatively, ensuring that the existing system is brought up to current standards with proper insulation, covers, and periodic servicing can significantly reduce potential risks.
Should I install a cold water storage tank?
In summary, while cold water storage tanks remain functional in many domestic plumbing systems, they are not without their drawbacks. Poor maintenance can lead to contamination, bacterial growth, and compromised water quality, all of which carry potential health implications. By prioritising regular inspection and servicing, proper installation, and, where appropriate, system upgrades, homeowners can safeguard both their water supply, wellbeing and health.
Sandford’s Plumbing, Heating & Renewables are your local experts in cold water storage tank installation, service and repair.
Covering Warlingham, Woldingham, Caterham, Purley, South Croydon, Oxted, Lingfield, Old Coulsdon, Godstone, Felbridge, East Grinstead and the surrounding areas. Why not give us a call for more information!
