Use it twice,
Bathtub: Buckets & Siphons
Did you know tha taking a bath uses 4 times as much water as a shower? many people think that because the shower is running it uses more water. But if you are committed to submerging like I am, you may want to use your bath water twice to ease your conscience. It's easy.
If your tub is above your yard you can siphon your bath or shower water with a garden hose. Just stick one end of the hose into the tub and weight it with a brick. To prime your siphon you will need a double-sided hose bib connector (I found one with a small ball valve which makes it easy to use). Connect it to your outdoor hose and turn the water on to fill the siphon hose until it comes through at the bathtub end. Disconnect the two hoses and water away!
If you don't have enough gravity for a siphon, you can use your bath/shower water to flush your toilet or water your indoor plants. Just keep your bucket or watering can handy by the tub. To flush the toilet, just fill your bucket and toss it down.
If you are watering plants, remember to use mild phosphate-free soaps and shampoos.
If you want to get into something a bit more complicated, you can re-plumb your house to flow through a small constructed wetland system. There is lots of information on how to do this on the web--I recommend the folks at Oasis and DamNation. Here are some simple tips I learned in constructing my system:
~ The easiest
water to recycle into your wetlands is shower, bath or wash water. The
water from your kitchen sink is full of food and oil which can get pretty
gunky and so requires extra filtering and maintanence.