JUST A COUPLE of weeks back, I went swimming in your drinking water. I was particularly sweaty and filthy, so it was great to plunge in and have a good thrash around.

The water in question was in the Wollondilly River, which snakes through some glorious, steep country about an hour west of Mittagong. From there it flows into Warragamba and becomes part of Sydney's water supply.

I want to assure you that I resisted the urge to urinate. I can make no such pledge, however, about the other swimmers - some of whom had that distant look in their eyes which speaks of either deep philosophical contentment or of under-the-surface weeing.

In order to avoid them, I swam lazily downstream. There I saw fresh horrors aplenty. A number of families were camped close by, no doubt intent on washing their cooking utensils in the river. Clothes, strung on tent ropes, indicated the recent washing of tracky daks and undies. Dogs gambolled in the shallows, wilfully shaking their fleas into the water.

As I write this, I take a slug of tea. Yes, I'm pretty sure I can taste a slight hint of labrador.

My point is not to besmirch Sydney's water, but to wonder why people are so horrified at the idea of a little recycled waste water being added to this mix. In reality, all water is recycled: it's been used before and will be used again.

The whole issue, you might remember, was covered pretty thoroughly back in fifth class in primary school. You probably copied out the little diagram, showing the rivers below, the clouds above, and a swarm of tiny arrows showing how the water circulates.

Good teachers made the intriguing point: there's no new water, so the water we drink today may have already passed through someone famous. Julius Caesar perhaps. A Tyrannosaurus rex. Or - my personal hope - Elvis.

This week Queensland Premier Peter Beattie announced a waste-water recycling scheme for his state. It took about two hours for the NSW Premier to rule out a similar move. Sydneysiders, it seems, are just too sensitive and fearful to even consider recycled water. We'd rather take seawater, strip it of its salt using bucketloads of energy, then pump the salty detritus back into the sea.

This, apparently, is because of the "yuk" factor - the idea that recycled water has had contact, at some point, with germy, pooey things.

So where, exactly, do people think we get our current water? Do they imagine it is freshly minted in heaven, whence it falls directly into the dam? Or that it's shipped in from the Evian plant in France?

I hate to break it to them, but Warragamba is already full of water that has had contact with germy, pooey things.

Take a hike in the hills around the Wollondilly and you can follow the story of a typical drop of Sydney water. The country here is deeply folded into a series of ridges and sharp valleys. Down at the bottom of each valley there's a tiny creek, which gurgles into life after rain.

A typical drop of water will fall on one of the steep hillsides, then roll downhill over wombat droppings, kangaroo poos and the odd cow pat.

Once in the creek it will sit for a while in a stagnant pond, along with some alarming-coloured algae, a few bonking frogs and a fair number of tadpoles.

After a bit more rain, the creek will finally shake itself into action and our drop of water will start to tumble over some slimy, moss-covered rocks and through mud-wallows constructed by black and bristly wild pigs, before finally dripping into the Wollondilly.

On the way to Sydney, it's cleaned by sunlight and by motion. Then it's filtered, lightly treated with chemicals and left to sit some more in the sunlight.

A glass of it, drunk straight from the tap on a hot Sydney day, is still my choice of the best drink in the world.

All the water we drink has had contact with dust and dirt and poo. It has fallen on a tin roof, splattered with dust and bird droppings; or been drawn up from the fetid earth using a bore; or it has tumbled onto a muddy field.

The only way to have a drop of water direct from the heavens is to stand in the rain, with your head thrown back and your mouth open. And even then, Elvis may have got to it before you.

The crucial thing - always - is that it's been treated properly before you drink it.

Which brings us to the question of the week: are we really going to burn all this power sucking the salt out of seawater, just because we weren't paying attention back in primary school when we learnt how water works?