SCULPTURE II / And not a drop to drink: Dalya Alberge talks to the artist William Pye about his work with water

Conservators of William Pye's sculpture at Expo 92 in Seville immerse themselves in their work. Every few days, they don wetsuits and snorkels and dive into the pool at the base of his 70m-wide wall of cascading water and set to work with tools more readily associated with swimming baths than with works of art.

Like all water sculptures, this one needs constant attention: sand must be filtered, the bottom hoovered, water treated and levels monitored. In Seville, where temperatures regularly soar into the high thirties, algae and bacteria spread particularly fast and the Expo frogmen must ensure that every one of the 1,400 nozzles in Pye's sculpture is clear: three million litres of water in his most ambitious piece to date pass through them constantly.

It is a complex operation. And algae are the least of the problems. Despite the endless possibilities of sculpting with water, it is so fraught with difficulties that few of the world's artists are prepared to tackle them; among them, William Pye and Angela Connor in this country and James Wines in the United States.

But in some 10 years of working with water, Pye has never let the difficulties dampen his enthusiasm. With his 1988 award-winning sculptures for Gatwick Airport, he made his name with a wider public. Anyone who flies from the North Terminal has to pass his enormous asymmetrical stainless- steel cones: the mirror-polished structure is caressed by a thin film of rippling water pulled by surface tension into rhythmical waves.

Although the cones have been likened to the nose of a plane, and suggest jet propulsion and vapour trails, the glistening quality of water - as beautifully hypnotic as flickering fire - seems to exert a soothing effect on passengers. Similarly, Expo's water- wall has a cooling effect on visitors. Water has always been renowned for its therapeutic benefits. Fountains made by the Ancient Greeks were thought to be endowed with magical powers of healing: one at Navplion was said to restore lost virginity and make mortal women beautiful.

The only claim Pye makes for the power of water is as a sympathetic agent for contemporary sculpture. 'Sculpture in a public place can often be alien,' he says. 'Water is like an ambassador, a lubricant for people's feelings.'

The word that most people feel for when they see a water sculpture is 'fountain'. 'If you approach a water sculpture, your first assumption is that it's a fountain. You don't think, 'What's that abstract?' ' says Pye. A more sensitive artist might find the term pejorative; whether people label his works as fountains or water sculptures matters not to Pye. 'Just language,' he says.

And yet 'fountain' can conjure up the most flamboyant Italian Renaissance masterpieces as well as the most modest drinking-trough in some drab town centre. Britain boasts some superb fountains, among them Joseph Paxton's 19th-century landscaping achievements at Chatsworth in Derbyshire. But fountain design fell out of favour this century.

It was by chance, on a rainy day in Wales, that Pye first became aware of water's sculptural possibilities. His eye was caught by the rippling formations of rainwater on a gently sloping road. He was mesmerised. Over time, he has simulated the 'endlessly repeating, yet infinitely complex and ever-changing patterns' over both smooth and textured surfaces of stone, steel and bronze.

Commissions were initially slow in coming. He found that architects and developers had to be dissuaded from plonking a sculpture next to some 'water feature' within their buildings. With the Gatwick commission, he prepared a video outlining the possibilities of a water sculpture, but when the site contractors heard he was making a cone with water flowing over it, they thought it sounded boring, he recalls. 'They expected jets and theatricals . . . When it was finally revealed, though, there was unanimous enthusiasm. One person even wrote me a poem.'

As so often, however, the most simple designs are often the most beautiful. Yet the simplicity of Pye's work is deceptive: beneath each Gatwick cone is a wigwam support structure. And below it is a plant-room with a 'massively complicated' concoction of pumps, pipes, a control panel and two 5,000-gallon tanks suspended from floor joists. The pumps are capable of sending 500 gallons per minute to the tip of the cone, while the control panel is linked to the Gatwick computer system, monitoring everything - including chemical solutions to treat the water against Legionnaire's Disease. The engineering team that looks after aircraft also maintains Pye's sculpture.

Every aspect of a water sculpture needs to be worked out with an engineer's precision. If an artist does not got his design absolutely right, it can have disastrous consequences, particularly if there is a room sited underneath a work. When they first turned on the tap for the Gatwick cone it 'leaked like a sieve', threatening the baggage conveyancing systems below, and the whole thing had to be redone. Another of Pye's pieces dripped into the office below and soaked the company's archives. In both cases, the commissioning companies had not properly waterproofed the base: Pye now takes full responsibility himself.

Such are the liabilities involved in working with water that Pye has to pay heavy insurance premiums. With last year's commission for the Colonnades shopping/office complex in Victoria, London, where water is played over a massive steel bowl seemingly suspended from 120 steel cables, more than 60 different contractors were working together on the site. Pye was warned that if, for any reason, he did not meet his deadline - delaying the other work - he could be liable for pounds 25,000 a week. He can also be sued if a sculpture is faulty.

To cope with the pressures - and keep his head above water - Pye had to become a limited company, teaming up with a professional architect. 'As an artist, it sounds crazy,' he says. But it is absolutely necessary. The most detailed contracts must be drafted to cover every eventuality to pinpoint where the responsibilities of artist and architect begin and end.

There is also the problem of designing a sculpture's plumbing. Each one has Heath Robinson- type designs - initially worked out on paper, then using clay models. With Chalice, the commission in Victoria, several engineering skills were required: Pye could not instal a plant-room (to which water returns) beneath the sculpture because that's where Victoria Station resides. A drainage system was devised to pump it up to the next floor and out of the building.

Although Pye inherited a basic understanding of engineering principles from his father, an academic engineer, he works with a professional team of water and structural engineers and swimming-pool and water-treatment consultants. The team will soon meet to start work on his latest sculpture, verticle cascades of water over both bronze and glass panels, commissioned by Mercury Communications. He is confident that his plans are watertight. They'll have to be. The site is over the entire telephone exchange.

Details of Pye's sculptures from The Studio, 16 Brodrick Rd London SW17 (081-682 2727)

(Photographs omitted)