Legionella Control

Heat and biocides. Water held above 60°C stops Legionella multiplying, and thermal disinfection raises the temperature further for a set time. Chlorine, chlorine dioxide, and copper-silver ionisation are the common chemical and ion-based controls, and HSE lists ionisation and chlorine dioxide as options. HydroFLOW® is not one of them: it does not kill Legionella. What it does is reduce the scale and biofilm that shelter bacteria from those controls, so the heat or biocide already in your system can reach them.

HSE guidance for hot and cold water systems is to store hot water at 60°C or higher, distribute it at 50°C or higher, and keep cold water below 20°C, because Legionella multiplies in the range between. Scale makes those figures harder to hold: around 1 mm on a calorifier coil can cut heat transfer by about 7%, so the plant works harder to reach temperature and stored water has less margin. Keeping heat-transfer surfaces clean is one of the simplest ways to protect the temperature regime. At MGEN Trois-Épis, a French hospital, the plate exchanger was still free of limescale after five years of treatment.

Biofilm is a layer of microbes and the slime they produce, bonded to pipe walls and other wet surfaces. Legionella lives inside it and inside the amoebae that graze on it, where it is shielded from heat and biocide. That is why a system can test clear after disinfection and then test positive again weeks later: the biofilm reseeds the water. HydroFLOW® disrupts the conditions biofilm needs to bond to surfaces, so existing biofilm loosens and is carried away. At a US hospital, biofilm that routine cleaning had missed was released from its ice machines within three weeks.

In two ways. Rough scale gives biofilm a large, sheltered surface to anchor to, in calorifiers, shower heads, TMVs and tower fill. And scale insulates heat-transfer surfaces, so hot water is harder to hold at temperature. HSE asks for shower heads and hoses to be cleaned and descaled at least quarterly for this reason. Treating scale at source reduces both effects: at the Palace of Parliament in Bucharest, visual inspection found about 50% less biofouling in hot-water pipework after six months.

Cooling towers are warm, aerated and full of surface area, so they need a biocide programme, monitoring and regular cleaning under the site's risk assessment. Those stay. HydroFLOW® reduces the scale and biofilm on fill, basins and condensers that biocide has to fight through. At a California hospital, biocide use fell by 75% with counts below 1,000 CFU, and blowdown fell by over 65%. At a large US office complex, bio-counts fell from approximately 100,000 CFU to below 1,000 within days. These are total bio-counts, measured alongside each site's own programme.

There is no single figure for every system. Action levels are set by national guidance and by your own risk assessment, and they differ between hot and cold water, cooling towers and healthcare settings. Any positive result should be reviewed with whoever manages your scheme. For reference, the sites on this page worked to their own targets: an Indiana hospital aimed for below 1 CFU/mL and reached it within 16 days, Grand Hotel Terme di Comano recorded every sample below 10 CFU/L, and a US office complex's cooling tower targeted a total bio-count below 10,000 CFU.

Yes, in most markets. In the UK, the Health and Safety at Work Act and COSHH apply, and the HSE's ACOP L8 and HSG274 set out how: a risk assessment, a written control scheme, a responsible person, and records. In the US, ASHRAE Standard 188 and the CDC's water management programme guidance set the expectation, and many states and cities regulate cooling towers directly. HydroFLOW® fits inside that scheme as a supporting measure. It does not replace any part of it, and it does not reduce your duty to test.

No, and we would be wary of anyone who claims it does. HydroFLOW® is not a disinfectant, and scepticism about electronic water treatment is often earned: the market has plenty of low-cost wrap-around devices with little evidence behind them. What we can show is narrower. The unit induces a patented ~150 kHz signal into the water, sized to the pipe and the application, and it reduces the scale and biofilm that shelter bacteria. Sites that kept their control scheme in place recorded the results on this page, including an Indiana hospital where Legionella fell from an average of 7 CFU/mL to below 1 CFU/mL. At a US apple packer, counts rose again when the signal was switched off. Judge it on a trial against your own sampling.

No. If your risk assessment specifies a biocide, ionisation or a thermal regime, it stays. What sites have found is that they needed less of it: a California hospital cut cooling-tower biocide by 75%, and a US apple packer held non-detect results at 10 ppm chlorine instead of 40 to 50 ppm. At Comano, HydroFLOW® was installed as part of a programme that also included thermal shock and purging. One site on this page does run without chemicals, and it had a reason: at Hotel Des Etrangers in Milan, the ageing pipework could not take chlorine, so the hotel chose HydroFLOW® with no chemical dosing in December 2017, and no Legionella recurrence has been reported since. That was the site's decision for its own system. Any change to your scheme is a decision for your responsible person, based on your own results.

Yes. The unit installs around the outside of the existing pipe, with no cutting, no drain-down and no interruption to supply. At MGEN Trois-Épis, twelve units went in on one day without interrupting the hospital's water service. Plan for the clearing phase: as scale and biofilm release, expect more material at strainers, filters and shower heads in the first weeks, and possibly a short rise in counts. Comano recorded exactly that before every sample fell below 10 CFU/L, and in Milan the detached deposits appeared at the taps, so schedule extra sampling and outlet flushing after installation. That also makes a trial straightforward: one unit on one system, measured against your own results.