A hosepipe ban has come into force for Thames Water customers, the latest operator to impose restrictions.
The company says the driest July on record has resulted in low reservoir levels.
The ban applies to around 10 million customers in London, the Thames Valley, north west Kent, and south Essex.
It means domestic customers are not allowed to use hosepipes for cleaning cars, watering plants or allotments, or filling paddling or swimming pools.
However customers are allowed to use mains water from a watering can or bucket instead of a hose.
Blue Badge holders, or those on the company's Priority Services Register can still use a hose for watering the garden, cleaning vehicles and maintaining ponds.
Sarah Bentley, Thames Water CEO said: "Implementing a Temporary Use Ban for our customers has been a very difficult decision to make and one which we have not taken lightly. After months of below average rainfall and the recent extreme temperatures in July and August, water resources in our region are depleted.
"Despite investing in the largest leakage reduction programme in the UK, customer demand is at unprecedented levels and we now have to move into the next phase of our drought plan to conserve water, mitigate further risk and future-proof supplies."
How will Thames Water enforce the ban?
The company says that if it becomes aware of customers ignoring the restrictions, it will contact them. People who repeatedly ignore the rules will face criminal action. They could be fined up to £1,000.
How long will the ban last?
A date has not been announced, but Thames Water says it will depend on the amount of 'prolonged and significant rainfall'.
Does it affect me?
You can enter any postcode here at Water UK to check
Thames Water has recently come under fire following a series of leaks and issues, including a fault at a treatment plant that left thousands without a water supply.
A Thames Water Spokesperson said: "We know it’s not acceptable to be losing so much precious water and we’re doing something about it. It’s not going to be quick, but we’re making progress and we’ve met our target for the last three years to reduce leaks by 10%. Our aim is to reduce our leakage by 20% between 2020 and 2025.”
“Since the extreme heatwave we have seen the number of leaks at least double compared to previously – partly due to ground movement and partly due to the higher pressures we pumped at to meet demand which hit a 27 year high in some places.
“We have 160 repair teams working tirelessly to fix leaks with activity taking place 7 days a week and over 280 people working round the clock and mainly overnight to detect leaks not yet appearing at ground level. We are repairing over 1,100 leaks per week – whether they are visible or hidden below ground.
“We prioritise repair work to ensure we focus on the bigger leaks first and importantly those affecting service to customers.
“We also have an extensive capital programme to help us fix more leaks in the future. In the next 3 years we will spend over £55m installing dynamic pressure management helping to modulate pressure across our network for varying demands, helping reduce leakage. And in the next 3 years we will spend close to £200m on replacing water mains.”