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020 4532 7773There is a rhythm to water hygiene work that follows the calendar closely. Certain risks are more pronounced at certain times of year, and for cold water storage tanks in London, the spring period is one of the most important windows to act. As ambient temperatures begin to rise and the colder winter months give way to April and May, the conditions inside uninsulated tanks and roof spaces start to change in ways that can significantly increase the risk of Legionella development.
Getting a professional water tank clean done in April, before the warmer weather takes hold, is one of the most straightforward and cost-effective steps a building owner or facilities manager can take to protect occupants and stay on the right side of their legal obligations.
This post explains why spring is the critical period for water tank maintenance, what a professional clean involves, and who should be prioritising it right now.
Cold water storage tanks are designed to store water at temperatures below 20 degrees Celsius. Below that threshold, Legionella bacteria are present in most water systems at very low, manageable levels and do not pose a significant risk. Once water temperatures begin to creep above 20 degrees, the risk profile changes.
In the winter months, tanks located in roof spaces or plant rooms are often kept cold by the surrounding environment. The ambient temperature does the work of keeping the stored water within the safe range. As spring arrives and ambient temperatures rise, that natural cooling effect diminishes. By the time summer is in full swing, tanks in poorly insulated or unventilated spaces can reach temperatures well into the Legionella danger zone of 20 to 45 degrees Celsius.
April sits at the beginning of this transition. Acting now, before temperatures have risen significantly, means any issues identified during the clean can be addressed while the system is still operating within the safer temperature range. Waiting until summer to discover a problem is a much less comfortable position to be in.
A professional water tank clean is more involved than simply draining and refilling the tank. The process follows a structured sequence designed to leave the system in a thoroughly disinfected and documented condition.
The tank is first isolated and drained completely. Once empty, the interior surfaces are physically cleaned to remove any sediment, scale, biofilm or debris that has accumulated on the walls, floor and fittings. This physical cleaning stage is important because no disinfectant, however strong, can reliably penetrate thick layers of sediment or biofilm.
Once the tank has been physically cleaned, a disinfectant solution is applied to all interior surfaces. The solution is left to dwell for the required contact time before the tank is rinsed thoroughly and refilled with fresh mains water. Water samples are taken from the tank and submitted to a UKAS accredited laboratory to confirm that the disinfection has been effective and that the water quality meets the required standards.
A full written report is produced covering the condition of the tank before and after the clean, the disinfection process and the laboratory results. This documentation forms part of the building's water safety records and demonstrates compliance with ACOP L8 requirements.
Our water tank cleaning service covers residential and commercial properties across London and follows this full process as standard.
Alongside the clean itself, a professional visit to the tank provides an opportunity to inspect its condition and identify any issues that need to be addressed. This is one of the practical advantages of scheduling the clean proactively in spring rather than reactively in response to a problem.
A tank inspection will check the condition of the lid and any covers, looking for gaps, damage or missing fittings that could allow debris or insects to enter the stored water. It will check the internal surfaces for signs of corrosion, cracking or deterioration that could affect water quality. It will look at the inlet and outlet arrangements, the overflow and any warning pipe connections. It will also consider the surrounding environment, including the condition of insulation, ventilation and any shared spaces that could affect the temperature of the stored water.
Where issues are identified, they can often be addressed at the same visit or scheduled for prompt follow-up. Catching a deteriorating tank lid or a failing ball valve in April is a very different situation from discovering the same problem during a heatwave in July.
The straightforward answer is that any building with a cold water storage tank that has not been professionally cleaned and inspected within the last twelve months should be booking one now.
Beyond that baseline, there are several situations where a spring clean is particularly important. Buildings that were unoccupied or had reduced occupancy over the winter, where water turnover in the tank may have been lower than normal. Properties where the most recent inspection identified any concerns that were noted but not yet resolved. Buildings that are about to enter a period of higher occupancy or increased water demand, such as offices welcoming staff back after a period of remote working or residential buildings ahead of new tenancies beginning.
Commercial properties where the duty holder has not reviewed the water safety plan recently should also consider whether the tank condition is reflected accurately in their current Legionella risk assessment. If the assessment is more than two years old or if the system has changed, a fresh assessment alongside the tank clean is a sensible approach.
Our Legionella risk assessment service is available alongside our water tank cleaning service, and many clients choose to combine the two visits to make the most efficient use of the access arrangements.
In some cases, a spring inspection reveals that a tank is beyond the point where cleaning alone is the right answer. Tanks that are significantly corroded, structurally compromised or no longer meeting current specifications may need to be replaced rather than cleaned.
If a tank replacement is identified as necessary, the spring period is again a practical time to carry out the work. Replacing a tank before the summer peak means the new installation is in place and properly commissioned before the highest-risk period of the year. Our water tank replacement service covers the full process, from removal of the existing tank through to installation, commissioning and certification of the replacement.
If you manage a commercial or residential property in London with a cold water storage tank, April is the right time to act. A professional clean now protects occupants through the warmer months, keeps you compliant with your ACOP L8 obligations, and gives you documented evidence that the system has been properly maintained.
To book a water tank clean, arrange an inspection or discuss whether a tank replacement might be needed, contact our team at London Water Treatment today. Call us on 020 4532 7773 or visit our water tank cleaning page for full details of what is included.
