When it comes to reducing water shortages in the UK, one idea scarcely gets mentioned: rainwater harvesting.

Rainwater can be drained off roofs and collected in storage tanks, which can be as simple as using a water butt fitted to a drainage pipe, and then used for watering gardens.

The rainwater can also be used for flushing toilets and washing clothes, which could save up to 40% of domestic water use – toilet flushing, for example, accounts for up to 35% of the average household’s water use.

The downside, though, is that without enough rain, the water harvesting system needs to switch to a mains water supply.