Cleaning and Disinfecting Your Cold Water Tank

Cold water tank cleaning and disinfection is among a variety of services designed to eliminate the risk of legionella and a variety of other bacteria growth in water supplies in your house. Since legionella species are prone to grow in stagnant water, it makes the cold water storage tanks one of the places where bad bacteria can grow. 

Water can also quickly become contaminated by a range of bacteria if the tanks for cold water storage are improperly or irregularly cleaned.

According to the Legionnaires' Disease Technical Guidelines HSG274 issued by the Health & Safety Executive (HSE), cold water storage tanks are subject to regular reviews, which will indicate whether cleaning, decontamination, improvement, or even replacement is required


Why do I need to clean my water tank?

Over time, cold water tanks, usually located in condos, basements, and airing cabinets, become polluted with waste, algae, scale, sludge, biofilm, fouling, wall molding, stagnation, corrosion & rust, foreign bodies, and plant formation. 

If contaminants reach or build up in our water supplies over time, they offer an environment for bacteria such as Legionella bacteria and E.coli to develop.

When to clean your water tank?

When and how often you should clean it depends a lot on whether the cold water storage tanks are potable or non-potable. Potable water storage tanks need to be maintained more frequently when they are used to provide drinking water for people.


  • The temperature of the inlet and outlet tanks must be checked at least yearly.
  • Internal inspection for indicators of potential contamination and debris must be carried out every 6 months for drinking water and every 12 months for non-drinking water.
  • Microbiological samples for drinking water should be taken every 6 months 
  • Water tanks should be sanitized annually (or more frequently if the inspector deems it necessary) for drinking water 


At the end of the day, domestic water tank cleaning is all about keeping proper water hygiene, human health and safe water supply systems.


New vs Old Water Tank

Due to age, cracking, damage, or rust, a fresh water tank installation is needed, and trying to fix such a water tank is something that even the most skilled DIY specialist should not attempt because it can be a long and expensive process. 

You should only authorize the cleaning, servicing, and substitution of your cold water storage tank to experts.