I just spoke to my sister who has just finished horticulture.

She said to be very wary of dumping greywater straight out into the garden - because although you are trying to help the enviroment, if there are any chemicals (even shampoo, soap etc), you will leech these into the soil and change the pH and over the long term end up creating a lot of problems with your soil & hence plant growth.

There are filtration systems for greywater, but she says these are VERY expensive (around 10k she said).

Just thought i would add this. We have started using our bath/shower water (shower is over bath so just put in the plug), then i take the cap off the downpipe and let it out that way (lot easier that going up and downt he stairs with buckets 50 times), but i'm allergic to soap & shampoo so that way avoiding the soil salinity problem.

HTH,
Yael