Are Flexi Hoses a Hidden Legionella Risk?
- Joe Pettigrew
- 22 hours ago
- 4 min read
The Overlooked Risk Inside Flexi Hoses
Flexible braided hoses, or flexi hoses, are a familiar sight in commercial plumbing. Whether they’re used to connect sinks, taps or appliances, their flexibility and ease of installation make them a popular choice. However, what many facilities managers don’t realise is that the very materials inside these hoses can create the perfect environment for Legionella bacteria to grow.
Legionella pneumophila, the bacterium responsible for Legionnaires’ disease, thrives in warm, stagnant water. But what significantly increases its ability to multiply is the presence of organic compounds that break down in water systems - and this is where many flexi hoses pose a hidden danger.
Why Materials Matter
Many flexible hoses are lined with low-grade rubber or synthetic materials that are not WRAS approved. Over time, these materials degrade, leaching organic compounds into the water. This degradation doesn’t just affect water quality - it feeds the bacteria.
In particular, degraded rubber:
Releases nutrients that act as food for biofilm and Legionella colonies.
Forms microscopic cracks and rough surfaces inside the hose where water can stagnate undisturbed.
Accelerates the breakdown of water quality in sections of pipework that are already prone to low flow or irregular use.
In essence, it’s not just about water temperature or stagnation anymore - it’s about what the water is coming into contact with.
Recognising the Signs of Material Degradation
What to Look for in Flexi Hoses
Facilities teams should regularly inspect flexible hoses for visible signs of wear. Common warning signs include:
Bulging, kinks, or soft spots in the hose.
Discolouration or cracking near fittings.
An unpleasant odour or visible slime around the connection.
But crucially, not all issues are visible externally. Even when a hose appears intact from the outside, internal degradation may already be taking place.
Non-WRAS Hoses: A Major Red Flag
The Water Regulations Advisory Scheme (WRAS) sets strict standards for materials in contact with potable water. Any flexi hose that is not WRAS approved should be considered high risk. Cheaper imported products often fail to meet UK safety requirements, using rubber compounds that break down quickly and unpredictably in varying temperatures.
If your asset register includes hoses without documentation of WRAS approval, they should be prioritised for replacement.
Biofilm and Bacteria: The Chain Reaction
From Rubber Breakdown to Legionella Growth
As rubber deteriorates, it encourages biofilm formation - a sticky layer of microorganisms that coats the internal surface of pipes and hoses. This biofilm acts as a protective shield, making it difficult to eradicate bacteria once present.
In fact, Legionella bacteria flourish within biofilm, especially in hoses exposed to temperatures between 20°C and 45°C. Even well-designed systems can’t mitigate the risk if the materials used are feeding the bacteria from within.
Microscopic Stagnation: The Unseen Problem
Degraded rubber also creates tiny ridges and hollows inside the hose, increasing surface area and allowing water to pool in pockets too small to detect visually. These microenvironments are:
Insulated from temperature fluctuations.
Protected from disinfectants or flushing.
Ideal for bacterial persistence.
This means that even regular flushing may not fully eliminate the risk unless the material source is addressed.
Alternatives to Flexi Hoses
Where practical, replace flexi hoses with rigid pipework, particularly in systems supplying drinking water or vulnerable user areas. Although more complex to install, copper and plastic rigid piping offers better long-term hygiene control.
If flexi hoses are unavoidable, use insulated, anti-microbial versions that are WRAS compliant and properly supported to avoid sagging or kinking.
When Should Flexi Hoses Be Replaced?
While there’s no fixed expiry date, best practice suggests hoses should be replaced every five years, or sooner if signs of deterioration appear. Including them in your scheduled maintenance plan reduces long-term risks, particularly in settings such as care homes or schools where water hygiene is critical. In environments like healthcare, flexi hoses should be seen as a last resort, and their replacement with hard piping considered a priority.
Inspection and Replacement Protocols
Create a log of all flexible hoses on-site, including manufacturer data, installation date and WRAS status. Then, implement a fixed schedule for:
Visual inspections (every 6 months).
Internal reviews or sampling (annually or as part of risk assessments).
Replacement every 5 years or sooner if wear is detected.
Include Hose Materials in Risk Assessments
Legionella risk assessments should go beyond usage and temperature profiles. Inspectors must now consider the material composition of components in the water system, particularly in areas with known stagnation or reduced flow.
Summary: Take Flex Hose Risks Seriously
It’s easy to focus on water temperature and stagnation when assessing Legionella risk - but the materials used inside your plumbing system are just as critical. Flexi hoses made from degrading rubber or unapproved compounds:
Fuel bacterial growth through nutrient release.
Provide shelter for biofilm to thrive.
Pose long-term risks even when flushed regularly.
By ensuring all hoses are WRAS compliant, routinely checked, and replaced on schedule, facilities managers can significantly reduce this often overlooked hazard.
👉 Want to go deeper? Visit our Flexi Hose Services page or our Legionella Remedial Work pages for more information on keeping your system safe from the ground up.
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