Legionella Bacteria in water butts

Water Butt

Recent investigations suggest 95% of UK water butts may be contaminated with Legionella bacteria, the bug responsible for the potentially deadly Legionnaires’ disease.

However, it would seem that the main danger comes when the water is used via a hosepipe and that using a watering can poses little risk.

Scientists working on behalf of Public Health England at the Porton Down facility have discovered most of the water butts in British gardens are likely contaminated with the potentially deadly Legionella bacteria. As part of a recent survey, they obtained samples from 113 water butts to determine whether the bacteria were present.

Just six water butts were discovered to be free from the potentially deadly bacteria.

How dangerous is legionella bacteria?
Most natural water sources contain the legionella bacteria; however, the bacterium will multiply in warm water conditions, above 20oC. The long hot summer we are experiencing means many water butts will provide the perfect conditions for legionella to grow.

The water butt will warm up in the sun, allowing the water inside to reach a higher temperature than would normally be the case, creating an ideal environment for bacterial growth.

Is water from a garden water butt safe to use?
Following the discovery that legionella was present in most of the water butts, the scientists working for Public Health England set up some water butts at their facility at Porton Down. They installed pumps beneath the water level, so they could see whether attaching a hosepipe would allow the bacteria to get out into the air.

The main danger when using contaminated water is that it may be released in the form of spray or aerosol which could then easily be inhaled. Worryingly, the experiment proved that using a hosepipe to get the water out of the butt produced thousands of bacteria in each cubic metre of air. In contrast, using a watering can to take water out of the water butt to use in the garden produced only a small number of airborne bacteria.

Should you continue to use a water butt?
Many water butts across the UK will have long since run dry, owing to several weeks without rain in many areas. However, those who do have water stored up and ready to use should consider using it in conjunction with a watering can to minimise the risks from creating spray.

The experiment at Porton Down has shown that putting a pump in the water butt and connecting it to a hose could be very dangerous indeed. This would be particularly true for those who have underlying health conditions or who are of an advanced age.

One man in Cromer, Norfolk died last year after using a hose to clean his patio. The hose had been left full of water out in the heat, where the Legionella bacteria could multiply.

Source: Legionella Control/



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Stephanie Hafferty

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