How often do cold water storage tanks need to be cleaned and disinfected?

Clean cold water storage tank

Cold water storage tanks should be kept clean and free from nutrients, including corrosion, scale and biofilm (HSG274 part 2). 

However there is in fact no definitive recommended timeframe for cleaning tanks, so they must be cleaned as necessary or if any of the following occur: 

  •  Installation of new water system or refurbishment of hot and cold-water system
  • Installation of new components to the water system 
  • When the hot and cold-water system has not been used for long periods and has not been flushed 
  • When routine inspection of the tanks deems it necessary because there is visible evidence of contamination or stagnation 
  • If the system has been significantly altered or entered for maintenance purposes 
  • If water samples taken from the system show there is evidence of microbial contamination 
  • During or following an outbreak of legionnaires’ disease associated with the system 
  • When a risk assessment has indicated a tank clean is necessary 


A chemical disinfection will typically be chlorine or hydrogen peroxide dosed to achieve the required ppm and maintained for at least an hour throughout the water system. The chemical is pulled through to all outlets and tested to ensure the entire system is treated effectively. 

After the disinfection and before the system is put back in use the disinfectant must be flushed from the system if using chlorine, or if using hydrogen peroxide be below the maximum level for potable water. 

Dantek have a team of highly trained technicians who carryout this type of work regularly. We are experienced in cleaning all sizes of tanks from small 50-gallon tanks in nursing homes to very large industrial size and everything in between. 

To get a quote for tank cleaning please contact our sales team who will be able to advise what to do at your site. 01454 417920