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ILTDU gives Eureka Moment

Horne ILTDU Thermal Disinfection Unit

During 2013, contamination by Pseudomonas Aeruginosa of a shower outlet at St Richard's Hospital in Chichester was identified.

The complete shower and inlet hoses were replaced and the problem appeared to be resolved.

However, two years later, during a routine 6-monthly test it was discovered that the colonisation had re-established.


The ILTDU gave us the opportunity to resolve our water hygiene problem, allowing us to provide our patients with safe, clean water at a time when our patients are most vulnerable Ralph Woolgar, Workshop Manager


To ensure continued patient safety, the Estates team then began to employ 30-day point-of-use filter handsets, which trap bacteria such as Legionella and Pseudomonas to deliver clean, safe water. At a conservative cost of £40 per filter, this can represent a significant ongoing cost per outlet.

Electronically controlled, the colonised shower had also, since its installation, been programmed to perform a daily duty flush for an extended duration. It could also perform a supervised thermal disinfection within the unit.

Repeated thermal disinfection operations over a series of months, as well as multiple hardware replacements (supply and outlet pipework, valve inlets and filters, shower hoses and a number of 'service units') however, failed to rid the outlet of the colonisation. Indeed, the P. Aeruginosa results actually worsened following every replacement.

The Estates team were almost at their wits' end, but had come to the conclusion that the colonisation originated in the upstream pipework and provided a constant reservoir that would repeatedly recontaminate the shower. Unfortunately, this pipework was, for some distance, embedded deep in a solid wall...finding and replacing the pipework was not a viable option; it was considered too disruptive for patients and healthcare staff. 

Just at this point, Ralph received a phone call from Trevor de Silva, our man in the SE. Trevor had something new and highly innovative to show to Ralph.

A new approach

Ralph's story is exceptionally common. Various methods are tried, and fail to manage the issue - explored in detail in our Pathogen Control in Hospital DWS paper.  More often than not, hardware replacement is deemed the ultimate solution ... yet, in time, and usually within 1-2 years, that also proves to be another, very expensive, failure.

It is now well-recognised that Pseudomonas Aeruginosa favours the last 2 metres of the supply pipework feeding tap and shower outlets. As such, thermal disinfection of the fitting alone will be insufficient to remove the colonisation. The colonisation extends up the cold supply pipework, therefore it needs to be challenged from a point further upstream to prevent rapid recolonisation.

The Horne ILTDU, In-line Thermal Disinfection Unit, permanently installed across the supply pipework, facilitates the regular and periodic thermal disinfection of the pipework and fittings - right down to the point of discharge.  This therefore includes the supply pipes, isolating valves, strainers, check valves, TMV and the outlet fitting.

The ILTDU works by opening a temporary path for system temperature (not less than 60°C) hot water to flow down the cold pipe drop, through the TMV and associated fittings, tap or shower outlet and to drain. Bathed fully in hot water, the TMV element responds as it should: expanding it moves the slide valve to shut tight on its hot water port and fully open its cold port to the temporary passage of 60+C water.

The water quality through the fitting can further be improved by additionally challenging the colonisation and its host biofilm through high velocity flushing. This process effects a change in the fluid dynamics and upsets the flow equilibrium; mechanically shearing excess biofilm from the pipe walls and removing it to drain - thus curbing the potential for downstream reseeding.


Due to the constraints of the solid ceiling, the ILTDU was installed some distance upstream of the problem shower, and well beyond those vulnerable 2 metres from the outlet.

Ralph had what he described as a 'Eureka moment' when, for the first time since the problem re-emerged, and after a single disinfection episode as per our recommendations: at 60°C for a minimum duration of 10 minutes, the results of the water samples came back clear.  CFU = 0

Initially Ralph operating the ILTDU on a monthly basis but, after consistent clear results has been able to relax this preventative regime to a quarterly thermal disinfection, paired with water sampling and analysis every 6 months.  There is no longer a requirement for point-of-use filters.

With such a significant reduction in testing, consumables, replacement hardware and associated man-power, Ralph is delighted with how quickly the ILTDU paid for itself, and continues to contribute savings for his maintenance budget.


Replacement Programme

St Richards Hospital, now part of University Hospitals Sussex, has settled into an on-going replacement programme for showers. As budgets and priorities dictate, problem shower outlets are being replaced with Horne T4 or T9 shower models, which include the ILTDU as a key feature for regular thermal treatment and ensuring continuing patient safety.

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