Most of us remember the paddling pools of childhood as modest affairs – but Britain’s homebound families are now buying supersized garden pools to cool off, and water companies are asking them to reuse the water to save resources in the coming heatwave.

Paddling pools are getting "bigger and bigger", a spokesman for Thames Water said, urging customers to reuse the water in the garden or to bathe their children or pets.

After a dry, cold April and a wet May, June has seen the return of balmy summer days, with temperatures above 20C set to continue throughout the rest of the month.

Water demand was up to a fifth higher than normal during last year’s hot May and June, the company said, urging gardeners to make use of water butts to water their plants in anticipation of another summer of high usage as people spend more time at home because of the pandemic.

Andrew Tucker, the water efficiency manager at Thames Water, said: "Although we’ve had a lot of rain this month and winter was pretty wet too, it’s still important to think carefully about our water use.

"Water butt owners will have had no trouble filling them this month so, as the weather gets hotter and drier, they’ll have plenty of water for their plants and won’t need to turn on the tap and draw on the drinking water supply.

"Even when river and groundwater levels are OK, we can’t always get it through the system at the same pace customers are using it when demand suddenly goes up 20 per cent as it did during the hot spell last May and June."

Currently, 10ft pools big enough for adults to swim in are on sale for as little as £60, with 7ft pools available for less than £20. Water companies are also asking customers to use "scum balls", which soak up body oils and lotions, to keep water clean, meaning it can be used again.

Peter Jenkins, the Water UK director of campaigns, said: "We know that some large paddling pools need as much as 2,000 litres of water or the equivalent of 25 baths. This is why our Water’s Worth Saving campaign is encouraging everyone to think about the water they use this summer. 

"In the garden and in the home, why not consider using water twice? The water from your paddling pool could help keep your plants healthy and the water you use to wash your vegetables could be used to clean up after dinner."

Gardeners have been asked not to use sprinklers, which can use the same amount of water in half an hour as a family of four does over a single day.   

In January, the British Swimming Pool Federation said demand for hot tubs had increased by 400 to 500 per cent last summer as families unable to go on holiday splashed out on accessories for the summer.

A spokesman for Water UK, which represents all water companies, said resource levels were currently normal across the country and that there was no risk of hosepipe bans. But companies are keen to encourage householders to be economical to avoid any risk of a shortage later this summer.

It came as uncertainty over foreign travel led many to give up hope of going abroad this summer, with a rush on domestic holiday destinations pushing prices in domestic hotspots.

Last week Portugal was removed from the green list of countries, and earlier this week, George Eustice, the Environment Secretary, said people should expect to "holiday at home" and not travel abroad unless "absolutely necessary".