The region's severe and prolonged drought could finally be felt across millions of domestic back yards, flower beds and allotments after Anglian Water confirmed its first hosepipe ban for 20 years.

The ban will be implemented from April 5 as a result of desperately low water reserves following the driest 18-month period in more than a century.

Anglian Water (AW) is one of seven water companies preparing to bring in restrictions in the wake of two unusually dry winters which have left reservoirs, aquifers and rivers well below normal levels.

The terms of the temporary ban, which begins on the Thursday before the Easter Bank Holiday weekend, will prevent hosepipes being used for household activities including gardening, washing cars, cleaning windows and filling paddling pools.

Domestic customers will still be allowed to water their gardens if they use a watering can rather than a hose, and to clean their cars, provided they use a bucket.

Businesses and other commercial operations will not affected, and there will be a small number of domestic exemptions to protect jobs, livelihoods and the infirm.

But AW managing director Peter Simpson appealed to all the company's 4.2 million customers to help save water, both at work and at home.

'This is the first time Anglian Water has imposed a hosepipe ban in more than 20 years, but we believe this is the most sensible and responsible action to take to help safeguard customer supplies for this year, next year and beyond,' he said.

'This is one of those times when everyone needs to pull together and help save water, as well as look out for relations, neighbours and friends who might struggle in some way – perhaps lifting a heavy watering can or bucket for example.

'We are not telling people to stop doing what they have to, but to adapt their behaviour to reflect the severity of the situation. The message is – do what you can.'

Mr Simpson said �14m had been spent during the winter to tackle leaks, with 24,000 leaks fixed since April 2011.

James Debbage, a former manager of Notcutts Garden Centre in Norwich who now runs Green Pastures Plant Centre and Farm Shop in Bergh Apton, near Poringland, said there were plenty of measures which gardeners could take during the ban.

'If we are not allowed to use hosepipes, people are going to have to adapt,' he said. 'They might have to forego things they would normally grow, and plant things which like the hot and dry conditions, such as geraniums, gazanias or portulaca. It may mean growing more things in pots around the house, where you can reach them with a watering can.

'The vast majority of people will abide by the restrictions, but there will always be one or two who will flout it.'

Beyond the restrictions in domestic gardens and driveways, the restrictions could also affect the watering of public flower beds and charity car washes, like the ones regularly organised by Norfolk Fire and Rescue Service.

Mike McCarthy, deputy chief fire officer for Norfolk, said: 'It would be a genuine shame if we had to stop our charity car washes as they are in support of the Fire Fighters Charity which is a very worthy cause. Having said that we understand as well as anyone what a valuable asset water is and why it must be conserved and will comply with any guidance or regulations as and when they are brought in.'

Janet Holdom organises the Fakenham in Bloom festival, which usually sees more than 100 planters and hanging baskets placed around the market town from June to September.

She said: 'We don't over-water the flowers – it is very controlled but it is done from a bowser. I have yet to find out exactly what the ban means, and whether our weekly limits would exceed the limits that AW are imposing. We would have to scrupulously adhere to those guidelines and until we know the specifics we don't know whether we might not be able to go ahead this year.'

A spokesman for Broadland District Council said the authority would not be affected by the ban, as its staff do not water any gardens, parks or lawn areas.

'We have no areas with bedding plants,' she said. 'The grounds maintenance only cuts grass and prunes shrubs and bushes.'

Across the country, it is estimated that up to 20 million homes face hosepipe bans in the coming weeks. Southern Water, South East Water, Thames Water, Sutton and East Surrey, Veolia Central and Veolia South East are also taking measures to preserve supplies in the parched South East and East Anglia regions.

Meanwhile Essex and Suffolk Water, which provides services to thousands of homes in South Norfolk and Suffolk, confirmed it has no immediate plans to issue a ban. But the company has not ruled out restrictions later in the year if the dry weather continues into the spring and summer.