Some 27% of the 2,004 adults quizzed in the survey for environmental charity Hubbub said they would be getting the paddling pool out for their families over the weekend.
With the trend for cheap, super-sized paddling pools that children and adults alike can enjoy, filling up the pool takes 530 litres on average, Hubbub warns, three times the usual daily amount each person uses.
That could mean 3.9 billion litres being used to fill up pools in back gardens across the country.
This, along with people taking longer showers and using hosepipes more, could lead to some households face a drop in water pressure as companies struggle to keep up with demand, Hubbub warns.
And the pools are not just for children, the survey by Censuswide suggests.
While just over half of parents with youngsters under 16 will be using a paddling pool, so will 16% of parents with children over 16 and 23% of people who are not parents, the poll found.
Trewin Restorick, chief executive of Hubbub, said: “It’s astonishing how much water it takes to fill a super-sized pool just to use it for a day.
“As well as being a huge drain on water supplies they can add to water bills and take hours to fill.
“No-one wants to be a killjoy, it’s really hot and we’re all looking for ways to keep cool and have fun in the sun.”
But he said there were lots of ways to do so while using “a bit less of one our most precious resources”.
Hubbub is urging people to take steps to make their use of paddling pools in the heat as environmentally friendly as possible.
Tips include not filling the pool up too full, inviting family and friends over to share the fun, and not draining the pool every night if you can cover it and use a water-sterilising tablet and if youngsters can be kept safely away from it when unattended.
People are also being encouraged not to tip used water down the drain, or even water the lawn, instead using it on plants or even giving the dog or car a wash.
Alternatives to pools could include buckets and sponges to soak and throw around, a water fight with water pistols or even heading to the beach if it is near enough, the charity said.