Don't use grey water.

Gravel reed bed for grey water.

I’d like to send out a quick message to all Bandwagon-Greenies. They’re the ones that suddenly give a crap about the world around them because they saw this DVD from Blockbuster about bad environmental stuff, or they saw some ad on TV about how our water is vanishing somehow. Not that those aren’t totally valid reasons to care, but they’re merely a starting point.
You shouldn’t get your science from ex-vice presidents OR shock-columnists, and you need to know your facts before you jump aboard the green train.

Here’s an important tip:
Don’t re-use grey water.

Just don’t. Install water saving devices, get a rainwater tank, flush when brown, collect clean shower water (otherwise wasted while it’s warming up), just don’t use grey water. Everyone’s doing it, but almost no one is doing it properly, and there are consequences. You screw up your soil with excessive sodium, and the best cure is to flush it with fresh water. Great water saving technique. Listen to talk-back garden programs, and you’ll hear time and time again stories of people destroying plants and soil with grey water. Just stop it now.

There are pathogens, E. coli, oils, reedbed filters, sodium quantities, differences between laundry and bathroom grey water – and which to use on veggies and fruit trees, food residues, pH, petrochemicals, phosphorus, the many and varied laws for grey water, the pointlessness of most legal grey watering systems, sulphur, storage issues, laundry powders vs. laundry liquids, living walls, the list goes on.

Here’s what you can do:
1. Throw the grey water onto grass straight after you collect it. To do more than that will require you to throw money, or your brain, at it. Grey water systems are complicated and elaborate, you won’t get much in the way of returns on your investment – they are purely for the committed.
2. Use Earth Choice, Aware, or Seventh Generation products. There are better ones, but it's likely you'll be able to find these.

As an example, here’s the effort a “proper” greenie would put into choosing a laundry detergent:
There is a round-up of laundry detergents in Renew (Jan-Mar 2007), and Choice (April) magazines, gathered by http://www.lanfaxlabs.com.au/, so you’d aim to use the product that has the lowest sodium, phosphorus and sulphur, then further checking needs to be done to ensure that isn’t tested on animals, not made with petrochemicals, Australian made/product/owned (product miles), make sure it has recyclable packaging, doesn’t have phosphates or other magical brightening/softening/perfume/colour chemicals, is any of that data reputable in the first place, and ultimately – can I buy it easily (most decent products aren’t even on the average supermarket shelves) and does it even work well (this will require testing). After some research and testing, you'll know what's good.