Water isn't working

Regarding Carl King's observations on the

's water shortage (

), it does seem ironic that as an island nation we should be facing serious drought, and I guess desalination plants seem a logical step.

However, as is often the way, it is not nearly as straightforward as we would like. Water supply authorities admit to losing staggering amounts of clean and purified drinking water through leaks in an antiquated network of poorly-maintained pipes.

Recently the leakage for Thames Water alone was said to be an incredible 915 million litres — over 200 million gallons — a day.

In fact, a recently proposed scheme for a desalination plant in East London was refused planning permission because London's mayor Ken Livingstone said Thames Water was 'leaking the equivalent of three quarters of Windermere every year'.

Now add to that all of the other UK water supply companies who are also leaking varying but significant volumes of water and it becomes blindingly obvious that this country has a huge problem.

As engineers, we already have and will continue to come up with innovative solutions to extracting clean water from the oceans. It does however raise the question; why spend a fortune on pumping to produce desalinated water if it is going into the same leaky supply network?

There are also pressing environmental issues. Desalination plants need plenty of power, regardless of the mode. No doubt as water costs rise, desalination will become a more attractive economic option and the arguments as to which method is the most efficient or cost effective will run for years to come.

What will become a serious issue, though, is what to do with the salt and other minerals that will be extracted.

A percentage may well find uses elsewhere, but the rest can't just be thrown back in the sea as it will become another form of pollution threatening marine organisms, fish and other invertebrates that have evolved over many millions of years in conditions that change at imperceptibly slow rates.

The oceans may have differing compositions worldwide, but locally they remain remarkably stable.

We have a moral obligation as individuals and as a nation to reduce our consumption of this precious commodity. As a matter of some urgency, we need to get our house in order to eliminate costly leaks in the supply network.

Our inability to store a natural resource that falls in the form of rain should also be questioned.

Engineers will invariably find solutions to all of these problems, but in order to make it happen we need the foresight and investment — now.

Paul Zimmermann

Bournemouth

Recent correspondents suggest desalination as a possible answer to our water shortage. I think this is mistaken, not because of the (significant) running costs, but because of the approach, which is equivalent to 'the roads are full — build more roads' way of thinking.

We must use what we already have more sensibly and efficiently. Why do we purify all our water, when only around 10 per cent of it is drunk or used in food preparation? Then we use the other 90 per cent of our 'potable' water to bathe, flush the toilet and wash the car. If this could be used twice, we could cut our water bill by 45 per cent, and hence reduce sewage charges.

'grey' waste water (already paid for) should be used to flush toilets, and 'green' rainwater to irrigate the garden and wash the car.The reason we don't is cost, because it does not make much economic sense for the householder to pay for the necessary hardware to do this. It will need legislation and/or more expensive water to make it happen.

It might be a start (and would be simple to implement) if we allowed all metered households to have some sort of free quota, then charged them extra for any further consumption.

For starters, here's a simple idea. a downstairs toilet cistern could be fed from a tank (in a false ceiling, perhaps) filled by gravity with grey water from the upstairs bathroom. One bath would thus flush eight to 10 toilets (depending on their design), a shower a bit less.

A level sensor and solenoid valve would ensure the holding tank never ran completely empty, topping it up from the main as necessary. That could save a significant amount, with almost zero running/maintenance cost. Would anybody care to take up this challenge?

Chris Finn,
Ideal Boilers,
Hull