One of the most common sources of nourishment for Legionella bacteria in a domestic water system is sediment, rust or other dirt. Therefore, an important control method is to ensure that cold water storage tanks are clean and free of corrosion. Here’s our simple four-step guide to keeping water tanks clean in your rental property.

Step 1: Inspection

Landlords or letting agents should inspect cold water storage tanks at least once a year as part of their Legionella risk assessment or monitoring procedures. If a tank contains significant dirt, sediment or rust, it’s time to give it a clean (guidance on how dirty a tank should be before triggering a clean can be found in HSE document HSG274).

Step 2 – Drain the tank

First make sure the mains water is turned off at the stopcock then turn on all the cold water taps and/or flush the toilet several times. This will empty the cold water storage tank and stop the flow of water. Alternatively, if you can’t locate the stopcock or don’t want to turn off the water supply completely, place a length of wood over the tank and tie the ball valve up to it in the closed position. The tank can now be emptied by running the cold water taps.

Step 3 – Scrub the tank

Wearing rubber gloves, use a scrubbing brush or similar abrasive tool to scrub the inside of the tank thoroughly. Make sure you get into the corners and pay attention to areas where there are joints or rivets. If there is scale on the internal surfaces you can use a household descaler to remove it at this stage. You can use household bleach (diluted to 1 tablespoon or 15ml per gallon of water) to disinfect the tank. Rinse really well with clean water.

Step 4 – Refill the tank

Once you are happy that the cold water tank is clean and free of sediment, make sure that the cold taps are turned off and then refill the tank by turning on the stopcock (or untying the ball valve). Make sure you replace the lid properly to prevent any debris falling into your lovely clean tank of water!

If you are concerned about the cleanliness of your hot water cylinder, we would advise calling out a plumber to drain and service it rather than tackling the job yourself.