The shower head, known as Safepurge and now on the market, is designed to eradicate the bacterium legionella, which is present in many hot water systems and can breed at an exponential rate in temperatures between 19 and 50 degrees Celsius. Hotels, hospitals and businesses - where showers may not be flushed out on a daily - basis - are most at risk but will circulate water above 50 degrees to minimise the risk of the bacteria multiplying to a dangerous concentration. Even so, a recent survey showed that legionella is present in more than half the UK's hotels and 70 per cent of hospitals.
The problem arises in "dead legs", the parts of the pipe where lukewarm water becomes stagnant, which provides a perfect site for a build-up of legionella. "A lot depends on the maintenance of the system, but it's just impractical to knock on people's doors and say `Have you used your shower today?' " says Mr Jones.
A green slimy bio-film, like algae, builds up behind the shower head, and all the stagnant water comes out into the shower head and into the cubicle. "It generates a fine mist in which the bacteria is suspended. Then it's down to a person's susceptibility," adds Mr Jones, 39, an engineer who designed air-conditioning systems before turning his attention to showers after a friend's death from Legionnaires' Disease.
The flu-like disease, which affects more men than women, got its name from an outbreak at a conference of legionnaires in the US in 1976. Another illness caused by a different strain of the bacteria, called Pontiac Fever after the site of its first known outbreak, is more virulent. Its most recent victim was a young World Cup fan who died after being infected. A conservative estimate puts the number of cases at 200 a year, of which around 15 per cent are fatal.
Mr Jones' solution was to devise a system that pops out the shower head and flushes away harmful bacteria before the bather is doused in water. The pop-out plate also extends away from the water supply in order to dry thoroughly, which in turn cuts down on legionella developing. The device has been tested by a leading UK teaching hospital, and shown to produce a spray of low concern, even when installed in a shower system heavily contaminated with legionella.
The beauty of the invention lies in its low-tech qualities, says Mr Jones, who has now added a business spin to Safepurge by teaming up with a long- time sailing partner - Steve Bennett, founder of Software Warehouse, this year's first-placed business in the Independent on Sunday league of the fastest-growing private companies - to market the product under the name Aqua Hygiene Products.
"The second part of the invention, where the spray plate protrudes by about five or six millimetres, took the longest. I had the pop-out going the wrong way for about three years. It seems obvious, but it wasn't. You just have to keep meandering and not get fed-up. I eventually got the idea for the control mechanism from a shampoo bottle. It was amusingly simple. I'm a bit of a Blue Peter graduate. I think you just have to be critical in not accepting what you see around you. Detail fudges the issue; hi-tech sometimes becomes an exercise in showing off. Low-tech is ultimately the long-lasting, reliable way, although everyone is hi-tech mad."
Mr Jones has already made headway in marketing his shower, which has cost around pounds 100,000 to develop: he presented it to a world conference on Legionnaires' Disease in June, and following the withdrawal of a product with similar claims in the early Nineties, Safepurge has no competitors. It will retail for around pounds 175, almost double the price of a normal shower.
Mr Jones is now designing a device to eradicate household dust mites, but has yet to reveal how it works.
"I'm not an inventor," he claims, "I just sit down and think. A lot of people have to learn to sit down and think."