Thousands of benefit claimants are being allowed to dodge hosepipe bans as millions of other Brits are placed under restrictions during the third heatwave of the year.Two water firms have given an exemption to those on the WaterSure tariff, a scheme for people on benefits who use large amounts of water for 'essential' reasons.They must either have at least three children in full-time education living in the home, or someone with a medical condition that needs significant amounts of water.People however cannot apply for the scheme because they want to water a garden with a hose or sprinkler, or refill a pond or pool with a capacity above 10,000 litres.Southern Water activated a ban for one million people across Hampshire and the Isle of Wight last Friday; while Affinity Water, which has 3.9million customers, will introduce a ban for parts of London and six counties in the South-East from Friday.Both firms have confirmed an exemption for their WaterSure customers but insisted this was intended to avoid confusion and prevent disabled people being put at risk. Southern has 17,742 customers on the WaterSure scheme, while Affinity has 3,146.Cambridge Water, which also imposed a ban, has an exemption but only for WaterSure customers whose disability makes it very difficult to use a watering can.Four other water companies are only allowing exemptions to the ban for Blue Badge holders or customers on the Priority Services Register for vulnerable households.