Double check valve
The common garden hose could pose a hidden danger to drinking water this summer, as Londoners reach for paddling pools and sprinklers during what forecasters say is set to become the hottest June on record.

The Met Office has issued a red extreme heat warning, its highest level, reserved for the most severe weather events, as temperatures are expected to reach 38°C in the capital this week.

With families looking to cool off, WaterSafe Register, the free directory of approved plumbers, is warning households about a little-known risk lurking in the garden: the humble hosepipe.

If the end of a hosepipe is left underwater in a paddling pool, pond or watering can, dirty water can be drawn back into the home’s internal plumbing – a process known as backflow.

Warm water left sitting in a hose over a hot week can also allow Legionella bacteria to build up, which can cause Legionnaire’s Disease if contaminated water droplets or mist are inhaled. The risk increases significantly during prolonged heatwaves, when garden hoses can reach high temperatures in direct sunlight.

The Met Office has issued a red extreme heat warning, its highest level, reserved for the most severe weather events, as temperatures are expected to reach 38°C in the capital this week.

WaterSafe Register is urging households to fit a simple safety device called a double-check valve to every outside tap and to follow a few easy habits when using water outdoors during the heatwave.

Top tips for safe water use this summer:

Don’t submerge the end of the hose in water, such as a pond, paddling pool, bucket or watering can
Keep a visible gap between the end of the hose and the water surface
Disconnect the hose from the tap and store it in a cool, dry place when not in use
Run it briefly without an attachment before each use, until the water feels cool – this is especially important after a hot day
Fit a trigger nozzle so it isn’t accidentally left running unattended
Fit a double-check valve to the tap and replace it every 10 years
Better still, use a bucket or watering can instead, where possible – and help save water during what is also set to be a very dry spell
Jonathan Samuel, Director of WaterSafe Register, said: “We are fortunate in the UK to have extremely high-quality drinking water, but it’s easy to introduce bacteria if our plumbing is in poor condition or we’re not mindful of the potential dangers.

“During a heatwave like this one, with temperatures set to break June records and hoses sitting in direct sun for days on end, the risk from legionella bacteria is real. We always suggest using a bucket or watering can where possible.

“If you do use a hosepipe, make sure your outside tap has a double-check valve and follow important safety precautions to help avoid the risk of contamination and potential illness.

“If you’re not sure your tap has the right protection, ask a WaterSafe-registered plumber to check it for you.”

To find a WaterSafe-registered plumber, visit watersafe.org.uk.