As of a week or so ago, my 20 year old townhouse now sports two new dual-flush toilets instead of the original single flush toilets.
This may need explanation in some quarters of the world (if my American friends are to be believed!). In Australia, most toilets are dual flush – one option for “Number Ones” and one for “Number Twos”! 
The advantage is that you can use a lot less water to flush liquids than solids.
(I should apologise at this point – this post is a little more “earthy” than my usual fare!).
The water savings I achieved are even more dramatic, though, due to improvements in the design of toilets in the last 20 years. Whereas my old toilets used 11 litres per flush, my new toilets use at most 4.5 litres (and only 3 litres for the “number ones” option).
The total cost was $1300. $700 for two new toilets, and $600 for installation.
So, I’ve done a few back-of-the-envelope type calculations and worked out how much water I’ll be saving. Care to guess? Go on, I dare you! 
16,000 litres a year.
Wow.
Kind of impressive. So I quickly moved on to figure the dramatic saving this would have on my water bill. Turns out this depends on whether I’m a big water user or not, but it works out to be between $8 to $16 a year.
Wow again. But this time, its the other sort of Wow…..
Now, I didn’t go into this to save money – I did it because it was the Right Thing ™. Glad I did it, and I’d urge everyone to do the same. 16,000 litres of water per household is a lot of water. But there’s a lot of people out there who are either unable to afford the cost of upgrading or (to be less generous) to self-focussed to do it unless theres something in it for them.
Full credit at this point to the ACT Government – they have a rebate program that gives you $100 rebate for doing the upgrade – there’s a few rules and conditions, and you can get all the details at http://www.thinkwater.act.gov.au. That amounted to a 15% discount, which is great.
Of course there are cheaper toilets out there (there are also way more expensive ones – do you know there are toilets that cost $1500 each?! How good can using the bathroom be?). And there may be cheaper plumbers. And many people may only want to upgrade a single toilet. Still, householders need to expect to pay at least a couple of hundred dollars.
Wouldn’t it be nice if water was charged at closer to its actual value? Imagine if, for instance, households were allocated some subsistence amount of water for free (or some small fixed sum), then a much higher cost for every kilolitre above that. I’m sure I’m grossly oversimplifying, but I imagine you could come up with some figures that match the average households current water bill. The difference would be that there is suddenly a big incentive to save water.
I’m sure this isn’t a new idea (although I haven’t seen any extensive discussion on it during my travels on the Net). What do you think?