What is the infection risk in water systems when using flexi hoses?
In 2010, the Department of Health issued an alert regarding the use of flexible hoses in healthcare environments. This followed a report that was received by Health Facilities Scotland (HFS), which stated that high levels of Pseudomonas aeruginosa and Legionella bacteria had been found in water samples taken from water outlets fed by flexible hoses, which were confirmed by testing of the hoses which revealed that the lining of the hoses was colonised.
The recommended actions within the published alert were to identify and risk assess any installed flexible hoses and, depending on the Legionella risk assessment outcome, replace them with a rigid piped system.
Legionella – What does the guidance say?
HTM04-01 Part A states that any materials that come into contact with the water in a hot and cold-water installation must comply with the requirements of the Water Supply (Water Fittings) Regulations 1999. To demonstrate compliance with these regulations, all non-metallic materials in contact with water should comply with the requirements of BS 6920.
Similarly, HSG 274 advises against using ethylene propylene diene monomer (EPDM) lined flexible hoses (tails) as these are a risk of microbial colonisation.
Flexible hoses should only be used for the following applications:
- To allow for the vibration of equipment
- To allow vertical movement for high low baths and sinks
- To facilitate maintenance of essential or bespoke equipment where no alternative is available.
If they are to be used, they must be kept as short as possible.
Why do we use flexi hoses?
Potable water systems frequently use flexible hoses to provide a quick and convenient link between fixed copper pipework and the asset or outlet it supplies. Research has shown a significantly increased Legionella risk within built environment water systems containing flexible hoses.
The use of non-approved materials often compounds this problem. Further research revealed that during the extrusion process, hard water had been used, and this led to microscopic pitting of the surface of the rubber, which provided an ideal environment for biofilms to form. It is also possible that the washers in the connectors are similarly affected.
Flexi hose considerations
New lining materials such as PE (polyethylene), PEX (cross-linked polyethylene), LLDPE (linear low-density polyethylene) and PVCC (post-chlorinated PVC) are now available as an alternative to EPDM lined hoses. Their long-term performance concerning the formation of Biofilm is yet to be established. Still, it is likely that they will only slow the growth of Biofilm and associated water-borne pathogens.
Where flexible hoses are installed, they should be risk assessed. Pseudomonas aeruginosa and Legionella risk assessments will often offer recommendations for any flexible hoses found during the survey stage. These should be prioritised relative to the risk rating (particularly in healthcare).
Determining which materials are present within the hoses is not always possible or practicable. The risk also depends on more factors than just the materials, including water temperature, water turnover, aerosol generation at the outlet, degree of exposure, and susceptibility of users.
There may be hundreds of flexible hoses installed in a building's water system, and recommended remedial actions may well be disproportionate to the reduction of risk achieved but may well be the only safe option depending on the degree of exposure and susceptibility of the end user.
Conclusion
If flexible hoses are installed.
- Carry out a risk assessment for the risk of Legionella proliferation, risk of dissemination, and risk of exposure to susceptible end users.
- If fitting them increases the risk, seek alternative means, i.e. rigid piping.
- Keep them as short as possible.
- Use only approved products.
- Flexible tails should not be used in healthcare premises other than in particular applications where fittings need to be moveable.
- If in doubt about performance, seek advice from the manufacturer. A reputable supplier will be more than happy to advise.
Feel free to reach out if you have any questions about the issues mentioned above or if you would like to consult with one of our experts on water hygiene.
Editors Note: The information provided in this blog is correct at the date of original publication – March 2025
© Water Hygiene Centre 2025
