Frequently Asked Questions
What does a commercial water treatment company actually do?
We deliver commercial water treatment and Legionella compliance services across Kent, South East London, and Essex. This includes Legionella risk assessments, demineralised water treatment, water treatment and hygiene, tank refurbishment, pre-commission cleaning, RPZ valve services, chemical cleaning, and consultancy support.
How often is a Legionella risk assessment legally required?
There's no fixed legal interval, but ACoP L8 and HSG274 both require assessments to be reviewed regularly, and in practice this means at least every two years for most commercial systems. A review is also required sooner if there's a change to the water system, a change of use in the building, or if a case of Legionella is identified. Duty holders who fail to review assessments regularly are at risk of enforcement action from the HSE.
We've noticed rising energy bills and reduced heat output.
Could our water be the cause?
Yes, and it's a more common cause than people expect. Scale and mineral fouling on plate heat exchangers and HIUs reduces heat transfer efficiency, meaning the system has to run longer or hotter to deliver the same heating or cooling. Left unaddressed, this shows up as higher energy consumption, more frequent maintenance callouts, and a shorter working life for pumps and heat exchangers.
Legionella Questions
Legionella Compliance FAQs
Who is responsible for Legionella control in our building, us or our landlord?
Under ACoP L8, responsibility sits with whoever has control of the premises and its water systems, referred to as the duty holder. In a leased commercial building this can be the landlord, the tenant, or split between them depending on what the lease and management arrangements say. Exactly how that responsibility falls in your specific case can be a legal question as much as a practical one, so if your lease doesn't make it clear, that's worth resolving with your solicitor or managing agent alongside getting an assessment done.
We've never had a Legionella risk assessment. Are we already in breach?
If your building has a water system capable of creating and dispersing water droplets, such as cooling towers, showers, or hot and cold water systems with areas of low use or stagnation, then a risk assessment should already be in place under the Health and Safety at Work Act and ACoP L8. There's no grace period tied to how long the building has operated without one. Getting an assessment done now closes that gap and gives you a documented record of taking the risk seriously going forward.
What actually triggers a Legionella outbreak, and could it really happen in our building?
Legionella bacteria grow in water between roughly 20 and 45 degrees Celsius, particularly in stagnant water, sediment, or biofilm inside tanks, pipework, and outlets that aren't used regularly. It spreads when contaminated water is aerosolised, most commonly through showers, taps, or cooling towers, and inhaled. Any building with hot and cold water systems has the underlying conditions for this to occur, which is why regular risk assessment and monitoring exists rather than being treated as optional paperwork.
Our building is small with just a few toilets and a kitchenette. Do we really need a legionella assessment?
Scale reduces risk but doesn't remove the requirement. Even small, low risk systems need an assessment to confirm that classification and document why the risk is considered low. This is often a quick, low cost process for smaller sites, and it gives you a defensible position if you're ever asked to demonstrate compliance, rather than an assumption that was never actually checked or recorded.
What happens if we're found non-compliant during an HSE inspection or after an incident?
The HSE can issue improvement notices, prohibition notices, or in serious cases pursue prosecution against the duty holder. Outcomes vary significantly by case and can include financial penalties and, in the most severe instances, custodial sentences. Beyond the legal exposure, an outbreak traced back to your building carries reputational damage that's difficult to recover from. A current, properly documented risk assessment is your primary evidence that reasonable steps were taken.
How often does our Legionella risk assessment need to be reviewed?
ACoP L8 and HSG274 don't set a fixed calendar interval, they require assessments to be reviewed on an ongoing, risk based basis. In practice this means a review whenever something changes: an alteration to the water system, a change in how the building is used, a change in occupancy, a confirmed Legionella case, or monitoring results suggesting your control measures aren't working. Many organisations still use a two year check as a practical benchmark for otherwise unchanged systems, but it's a sensible habit rather than a legal deadline, and it doesn't replace reviewing sooner if a trigger event happens.
We've had building work done recently. Does that affect our existing assessment?
Yes, and this is one of the most commonly missed triggers. Any change to the water system itself, or to how the building is used, can invalidate the assumptions behind a previous risk assessment. New pipework, altered water systems, or a change in use such as office to residential all warrant a fresh review rather than waiting for a routine check.
Our building has been partially empty for months. Is that a Legionella risk on its own?
It can be a significant one. Water sitting unused in pipework and outlets is exactly the stagnation Legionella bacteria need to establish and grow, so extended vacancy or reduced occupancy is a recognised trigger for reviewing your risk assessment and control measures, even if nothing else about the building has physically changed.
Demineralised Flushing FAQs
Water Treatment FAQs
Why do our pump seals keep failing even though the system has corrosion protection?
Corrosion inhibitors protect metal surfaces from oxidation, but they cannot remove calcium or magnesium hardness from the water. Mains water across London and the South East typically carries 250 to 350 ppm of hardness, and that hardness keeps circulating even in a system dosed with inhibitor. Over time it deposits as scale on pump seals and moving parts, which is why premature seal failure is one of the issues we're most commonly asked about on systems that appear, on paper, to be properly treated.
Our HIUs are fouling and losing efficiency. Is that a design fault or a water quality issue?
Heat Interface Units run tight tolerances and small internal passages, so they're more sensitive to hardness than the boilers and pumps of older systems. When mains make up water enters a closed system without demineralisation, dissolved minerals gradually foul the HIU's internal surfaces, reducing heat transfer and forcing the unit to work harder for the same output. This is generally a symptom of untreated make up water rather than a fault with the HIU itself.
We've noticed rising energy bills and reduced heat output. Could our water be the cause?
Yes, this is a recognised link. Scale and mineral fouling on plate heat exchangers and HIUs reduces heat transfer efficiency, meaning the system has to run longer or hotter to deliver the same heating or cooling. Left unaddressed, this contributes to higher energy consumption, more frequent maintenance callouts, and a shorter working life for pumps and heat exchangers.
What actually happens during a demineralised balanced flush?
It's a controlled process, not a simple drain and refill. Demineralised water is introduced into the system continuously while the existing system water is simultaneously displaced and discharged, so the system stays operational throughout rather than being emptied. This progressively reduces conductivity, hardness, and total dissolved solids, typically down to under 100 µS/cm conductivity and under 20 ppm hardness, while using significantly less water than a full drain and refill.
We already have a treatment contractor. How do we know if our system's water quality has drifted since it was last treated?
This is exactly what ongoing monitoring is for. As systems age, make up water gradually reintroduces hardness and dissolved minerals even after a successful initial treatment. Regular on-site analysis, checking conductivity, hardness, TDS, iron, copper, and inhibitor residual, catches that drift early through trend reporting, before it turns into a fouling or corrosion problem you can see or feel.
Is this treatment only relevant for new installations, or can it help an existing system that's already showing problems?
New or altered pipework goes through pre-commission cleaning and demineralised flushing as standard before commissioning, in line with BG29 guidance. For an existing system already showing scale related symptoms such as fouling, reduced output, or seal failures, the same chemical cleaning and demineralised flushing process can generally be applied to correct water quality without replacing major components, though the right approach depends on the condition of your specific system, so this is worth discussing with us directly rather than assuming a one size fits all fix.
If demineralised water has no minerals in it, how is the system protected from corrosion?
Once the demineralised flush reaches the required water quality, the system moves into a separate final protection stage. It's dosed with a high performance molybdate corrosion inhibitor and, where needed, a closed system biocide, then circulated and tested to confirm it sits within target parameters for conductivity, pH, and inhibitor concentration. Low mineral water combined with correctly dosed inhibitor is what gives you both outcomes, minimal scale forming potential and strong corrosion protection.