The Principles of Medical Device Decontamination

To ensure that there is a constant supply of cold water through the hospital the cold water is stored in cold water storage tanks. Typically, the volume of cold water stored should be minimised with a nominal 12 h on-site storage recommended. Storage can be complicated where multiple cold water storage tanks, known as cisterns, may be connected. This requires care in the jointing materials and connecting pipework to ensure that the water flows through each of the cisterns to avoid stagnation in any one cistern. Water movement, along with chemical and microbiological monitoring, should be routinely conducted to ensure compliance with current standards and prevent deterioration in water quality.

To maintain optimal water conditions, storage tanks should be:

• Fitted with close fitting lids and insect screens fitted to any pipework open to the atmosphere. • Sited in a cool place and protected from extremes of temperature by thermal insulation. Piping should be insulated and be easy to inspect. • Supplied with the water supply at one side of the tank with the water outlet at the other side and close to, or in the bottom of the tank. • Inspected on an annual basis to check the condition of the water and the tank, which should be clean with an absence of debris or contamination.

Issues to consider with the water system to prevent microbial growth

Water for the washer disinfectors should be taken from a mains supply that is continually flowing to provide water of a satisfactory quality.

Plastic materials used in tanks, pipework, valves, O-rings and pumps should be Water Regulations Approval Scheme (WRAS) approved to minimise microbial growth of Legionella pneumophilia , Pseudomonas aeruginosa or non-tuberculous Mycobacteria 2 and other environmental microorganisms. Water should be kept moving and dead legs, where water will be stagnant should be removed. Design should ensure that all tanks, pipework, fittings, pumps etc. are free draining where possible.

In most cases, biofilms will become established and, in some circumstances, will only be removed through the replacement of contaminated components.

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