'Out of site and out of mind' it is easy for one of the most important parts of the water system to become neglected. Often located in loft spaces with difficult access conditions, cold water storage cisterns can become the ideal haven for Legionella.

The HSC ACOP L8 says that water systems should be cleaned and disinfectded;

•  if routine inspection shows it to be necessary

•  if the system or part of it has been substantially altered or entered for maintenance purposes in a manner which may lead to contamination

•  during or following an outbreak or suspected outbreak of Legionellosis

Common problems with storage systems are:

• Located in difficult to reach areas, they are rarely inspected at 6 monthly intervals as required.
• In warm roof spaces, the water within the cistern has the potential to exceed the recommended maximum of 20dgC
• Old cisterns often contain elements of unsuitable material, such as wooden lids, which encourage bacterial growth.
• Over-storage can occur as the tank may originally have been installed to service more people than work there currently, leading to poor turnover.
• Stagnation can occur where the cistern pipework has been configured so that the inlets and outlets are both located at the same end of the cistern.
• Incorrectly linked cisterns can lead to stagnation where water fails to flow evenly through both vessels.

Click Here to See an Example Tank Clean

• As debris and silt enter the cistern either via the mains or where cistern lids are not fitted, the organic matter provides a nutrient source for bacteria
• Without regular cleaning, Biofilm may develop to provide shelter for bacteria

Nemco Utilities employ trained and experienced technicians to carry out cleaning and chemical disinfection of storage cisterns and the water services they feed. Thermal disinfection can be conducted on hot water systems where appropriate. The process follows the methods recommended in L8 and BS6700 and involves draining and cleaning the tank to remove sludge and Biofilm before refilling and chlorinating the water to 20-50mg/litre. The treated water is distributed throughout the system and allowed to stand for a period of time before the chemical is neutralised. The entire system is then thoroughly flushed before being re-commissioned.

Difficult Access is NO problem! A number of our staff are highly trained to cope with difficult access conditions. Qualified in confined space working, rope access for working at height, together with the use of specialist access equipment means that most jobs are possible.