Water companies have been experiencing “unprecedented peak demand” amid the extreme heat.
People are being encouraged to “carefully consider” their water usage, and urged not to waste it in the high temperatures.
Water UK said that the “most intense demand” is across the south of England but that “pretty much all companies are seeing elevated demand at the moment”.
The industry body has members across England, Scotland, Wales and Northern Ireland.
A Water UK spokesperson said: “Water companies are seeing unprecedented peak demand for water during this extreme hot weather event.
“We are urging everyone to carefully consider the amount of water they are using at this time.
“All water companies have been contacting their customers directly with information and advice to help them reduce their water usage.”
Our call is basically ‘stay hydrated, look after your health, but please use water very very carefully and don’t waste it’— Andrew Tucker, Thames Water
Southern Water said that on an average day it supplies around 540 million litres to its 2.6 million water customers – but that the peak level so far this summer has been 657 million litres.
It added that it is possible the heatwave 2018 record of 671 million litres might be broken this year.
United Utilities, a water provider in the north-west of England, said it is “working flat out to feed (water) into the pipe network as fast as it is being used” and that it expects to supply around 230 million extra litres of water on Monday – which is normally enough to supply both Liverpool and Manchester combined.
Water demand reduction manager for Thames Water, Andrew Tucker, said the heatwave has led to demand being “at near record level”.
He said while Thames Water is not currently considering any water restrictions, that could change if there is little rainfall in the coming months.
Speaking to BBC Radio 4’s Today Programme, he said: “We’re doing pretty well.
“We know exactly how much water we’ve got in the system, and that’s both in our rivers, the aquifers underground or groundwater aquifers, but also how much we have in our reservoirs.
“We balance that with how much demand we’re seeing from homes and businesses but at the moment that demand is at near record level, as we were expecting.”
He added: “We’re not expecting to need to introduce restrictions on water at the moment.
“But we know how much water we’ve got, and with people using more at the moment, we are getting through it faster than we would like.
“If we don’t receive rainfall in the coming months that situation may change but we’re staying on top of it every single day.”
Mr Tucker said nine of the past 11 months have seen “significantly below average rainfall” and described the peak demand for water at the moment as “extraordinary, there’s no doubt about that”.
He urged people to be careful with their water usage, especially in their gardens.
He said: “Once we fall back into a normal routine and we understand what customers are doing in homes and businesses just as a normal weather situation, we’ll be in a better position to say how we’re going to stand for the rest of the rest of the year.
“But we would certainly like rainfall but it’s those little things that people do in the backyards at the moment, those back gardens that really make a difference.
“So our call is basically ‘stay hydrated, look after your health, but please use water very very carefully and don’t waste it’.”
Water-saving tips include not letting the taps run when brushing your teeth or washing dishes, only using the dishwasher when full, swapping the garden hose for watering cans instead, letting the lawn go brown, reusing paddling pool water and not washing your car.
