Mineral water is this summer's manna from heaven: for thirsty city workers and bottling firms intent on cashing in, writes Vicky Ward
There is one liquid in this long hot summer that is preferred to any other. People are consuming it with all the eagerness of the Old Testament Israelites devouring heaven-sent manna. Bottled water. No longer a luxury but a necessity. And the mineral water production companies know it.

In the unlikely setting of the backyard of a glorious country manor house in the middle of the Hertfordshire countryside the employees of Chiltern Hills Mineral Water are hard at it. Workers clad in white coats, hats, gloves and masks do not even lift their heads as they pile bottle after bottle on to the whirring machines that pipe the water into the bottles from the header tank. This is where the water, from a well 300ft below the ground is stored. The packagers, receiving the filled, sealed, labelled bottles at the other end of the system are the same. Judging by the state of the canteen, they barely stop for a lunch break.

It looks like a tornado just whistled through it. Newspapers left open at page two, half-smoked cigarette butts lying in ashtrays, and bits of paper posted up everywhere with the word "bonus" marked in big letters. Of a holiday rota for the summer months there is no sign.

For these 25-odd production workers a long hot summer means one thing: frantic work. "Orders have gone through the roof," explains Dee Ward, the 30-year-old MD of Chiltern Hills Water Coolers, whose family owns both the manor house and the site. (A bore-hole was drilled in their garden as long ago as 1870.) "Last week I had to hire four extra drivers and we are working through the night to get our deliveries out. Our clients tend to realise two days after one delivery that they have not ordered enough so they ring up requesting more."

Last month he delivered a total of 6,000 refill (22-litre) bottles to offices, shops, and gyms for his water-cooling systems. In the first two days of this month he delivered 2,500. Before that the average was 4,000 a month. He has also sold 60 coolers in 48 hours and the target for the whole month is only 120. Each refill costs pounds 6.75 a bottle, making this a very profitable summer.

"We haven't seen such demand for five summers," explains bottling production director Martin Dyer. "It's not just that the supermarkets want twice as much water as usual, they want it twice as urgentlyl. Normal production is a quarter of a million bottles a week; right now we're producing more than double that."

But the weather brings hazards too. Heat, explains chief microbiologist Peter Marrett, means that more bacteria breed in the water, which they are not allowed to add to or cleanse in any way. "The water in the header tanks has to be the same pure water as the stuff which flows 300ft under the ground, but we have to test continually that it is pure at every stage." A bewildering array of syringes and gauges testify to the technological expertise required to bring this "natural" water to your table. "We have to have screens over the water in the header tank in case an insect were to fly in or a window were to break. In the summer there are more risks of contamination. "

From human sweat, for example. Despite the air conditioning and the coolness of the bottling plants, the workers perspire heavily. That is why they all have to wear plastic gloves, and white hats and coats. Those with beards have to wear surgical-type masks too. The minimum bonus target, just for the team that bottles the 2-litre carbonated stuff, is to bottle and package 21,888 bottles a day. "Most days they achieve it," explains their supervisor.

For six weeks the daily shift of eight hours (8am till 4.30pm) has been extended to 8.30pm as well as two eight-hour shifts at weekends. Which, with the bonuses they bring, makes all this hard work worthwhile. "I'm very tired," sighs one man, perspiring heavily, "but happy. I certainly don't want this weather to end."