Homeowners told to ration water supplies during a heatwave were forced to watch Britain's biggest solar farm siphon up to 500 gallons a day from the mains to wash its panels, The Mail on Sunday can reveal.

South East Water blamed soaring demand during May's hot weather for leaving homes in Whitstable, Kent, without running water for more than three days after its reservoirs reached critical levels.

But the company continued to allow Cleve Hill Solar Park, five miles away in Graveney, to draw from the network throughout the outage to clean dust and dirt from its half a million panels. 

Tensions boiled over when villagers spotted a mobile water tank filling up at a roadside standpipe and challenged the driver, who confirmed the water was bound for Cleve Hill.

The solar farm was drawing from the mains at least once a day until May 28, when 15,000 people across Kent still had no water supply.

Many residents were left queuing in 32C temperatures to collect emergency bottled supplies, while businesses missed out on thousands of pounds of seasonal trade after being forced to close on what were expected to be some of the busiest days of the year.

John Waller, the manager of Seasalter Holiday Park, questioned why the water supplies destined for the farm were not being delivered to elderly residents in need.

'Myself, my partner, our daughter and the dog live here and we couldn't wash, couldn't shower and couldn't flush the toilet for three-and-a-half days,' he said. 

'Then you find out they are filling up out of the water mains to wash their panels – it is just outrageous.'

Chris and Katrina Goater, who run The Four Horseshoes pub in Graveney, said the park's water use had become the main talking point among their customers.

'We saw the vans going up and down, filling up at the standpipe at the end of the road – it was happening about once a day,' Mr Goater said.

'When you have all these people who can't even brush their teeth, you just think, this isn't right. Why are they being given priority?'

Cleve Hill Solar Park had an agreement with South East Water allowing it to draw from the standpipe, but has since apologised and stopped after locals' complaints.

The Whitstable outage is the latest in a string of supply failures to hit South East Water, which left 24,000 homes in Tunbridge Wells without drinking water for two weeks last November and nearly 30,000 homes dry in January.

South East Water - whose departing boss David Hinton was awarded a £115,000 bonus last year on top of his £400,000 salary - said it was 'sincerely sorry' for the disruption.

However, homeowners and businesses have said not enough is being done to resolve the issue, which they claim is the result of faulty infrastructure, rather than the heatwave. 

Sarah Simmonds, operations manager at Crescent Turner hotel in Whitstable, says the water shortages have cost her business an estimated £20,000. 

She said she had back-to-back weddings booked during the outage and they had to bring in two tanks of water - at a cost of £8,000 - to ensure they could go ahead. 

Ms Simmonds told the Mail: 'We are an 18-bedroom boutique hotel and restaurant so to suddenly have no water going into a weekend, that was just horrendous. 

'What we had to do was react very quickly, we hired in a water pillow and events showers. 

'We couldn't flush our toilets, we couldn't clean our rooms and in order to facilitate the weddings it cost us an extra £8,000.

'We had to employ more kitchen staff to ensure that we could wash safely and buy extra hand sanitizer. 

'We also had to get our receptionist to write letters explaining to people that you can't flush the toilets. 

'Try explaining that to an elderly grandma who is here for her granddaughter's wedding - it didn't go well.' 

South East Water's head of business customer services, Rachel Baker, said: 'The solar farm has the relevant water use permissions and the amount of water being used is in line with what we would expect a site such as this to use.

'We are in discussion with the farm's contractors to understand how they may be able to reduce their water use.'

A Cleve Hill spokesman added: 'The panel cleaning will be completed by the end of June.

'We thank the local community for raising these matters and apologise for any concern caused.'