The cost would be another pounds 2bn a year, on top of the pounds 2.8bn a year the industry is now spending in England and Wales. The industry is losing 24 per cent of its water through leakage, and estimates a cost of pounds 400m to lop off each percentage point.
The job would entail speeding up the refurbishment and replacement of mains and improving leakage detection and repair. Local mains and service reservoirs would need re-engineering to cope with hot weather surges in demand; large storage reservoirs would be needed as well as transfer schemes to shift water from wet Wales and Scotland to dry eastern and southern England.
Under present rules, this is not going to happen this century. After five years in which water bills rose by an average of 5 per cent above inflation, industry regulator Ian Byatt last year bowed to public exasperation and restricted increases to 1.5 per cent above inflation for the next five.
So is England (almost all recent British droughts have been English ones) doomed to repeated hose pipe bans?
It depends on the weather. Since early June rainfall has been only 40 per cent of the average and unless we have very heavy rain soon, this summer will go down as the driest since records began in 1727.
Yet today's shortages began not because of record dryness - in spring, reservoirs, rivers and aquifers were brim-full - but because of record demand. As sprinklers and hoses were turned on all over the country, water companies reported demand rising by 50 per cent above normal.
It has gone on and on, and now hose pipe bans affect more than three million people in Cornwall, southern England and West Yorkshire. If, as expected, North West Water declares its own on Tuesday that will add another seven million.
It was Labour that put leakages into the debate, producing official figures showing that two of the four water companies with shortages, Yorkshire and North West, have the largest losses from their mains - 32 per cent and 30 per cent respectively. If they plugged the leaks they could cope with drought and rising demand for years to come.
``We just laugh at the idea of cutting leakage to 15 per cent overnight,'' said a spokesman for Yorkshire Water. ``We'd be digging up all the roads and the place would look like the Somme.''
Experts say a zero-leakage system is impossible; any lower than 10 per cent and the costs outweigh the benefits.
One company, Southern, is working towards that, having cut leaks from 26 per cent at the time of privatisation to 14 per cent now. Yet Southern still had to bring in hose pipe bans this summer.
``It was a double disappointment,'' says Stuart Derwent, managing director at Southern Water Services. The experience will make Southern reconsider the case for using water meters for charging in order to control demand. "Clearly, we will now be looking at that again,'' said Mr Derwent. ``We have to take a new view of our customers.''
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