In Ontario you would be asking for trouble to mention this to an inspector. Like you I do plan to plumb for grey and black water separately and combine them as far downstream as possible for separation/re-routing at some later date. I haven't decided if that will be inside or outside just yet.

Listen to perfesser...your asking for trouble. it will be considered waste septic water if it goes down the drain and if divert anywhere else, I guarantee, will contravene a number of different local by-laws.

Here's a link to a proven system... http://www.rainharvest.com/aqua2use-greywater-recycling-system.asp

Thank you for the inputs so far. Unfortunately everyone agrees, grey water (evidently) is evil.

Grey water has not been routinely permitted for residences, only for a few commercial operations. Evidently the bacterial risk is too high from washing my hands.
http://www.municipalaffairs.gov.ab.ca/1176.cfm

Nearly as frustrating as looking into doing rainwater collection for domestic usage. The official documents state that it can only be done for irrigation and flushing toilets. Unfortunately the world revolves around urban areas, and the primary concern is that any backflow might contaminate the municipal system. This is absurd....but it is the world we live in.
http://www.municipalaffairs.gov.ab.ca/CP_RainwaterHarvesting.cfm

In Australia, my relatives were required to show capacity for rainwater collection adequate for all domestic purposes prior to being issued a building permit. Off the roof, straight into the tank, and from there back into the house, the taps, the toilets, the showers, everything.

Considering the abysmal quality of well water here in Alberta, we are essentially required to use water resources that leave mineral deposits on all devices. Or require massive waste of water in order to soften it.

http://en.wikipedia.org/wiki/John_Todd_(biologist)

Here is the link to wikilinks notations about John Todd, the acknowledged pioneer in the field of bio/phytoremediation, and the development of the "living machines " which are used on larger scales for handling blackwater/greywater.
The principles can be used in a homescale, but sizing of containers and processing volume are all variable.
Still, if the right plants/components can be fitted to any bioregion below 45degrees lat., there's no reason it can't be done.
It's something which i'm checking out more as i plan to implement in future when there's money to do it.
It's still an approval decision at the local level, but using precedents from all over the world, should increasingly persuade officials, especially citing ultimate water and cost saving records. I know of a school which has been using this for their grey water and recycling it for use in their toilet system...for 20 years now.

ps. i've recycled our laundry water and watersoftener rinse cycle water just as long , by using a covered bathtub slightly higher than the basement toilet, and a gravity flow /float valve to supply the toilet. It does smell a bit sometimes if left sitting too long. So, we're using that volume twice before it exits down the toilet.
That's in the city. In the country , compost toilet with pee separation is the most effective handling for solids with peat/sawdust.
Pee can be diluted and applied to berry bushes, etc. Solids can self-process over a year, in a rotation of removable, lidded barrels .

Well your post is old, but if your still around....Rain water,yep no problem, greywater yep no problem, of course I dont know where you are, but if you cant go head to head with them over under and around works...lots do it....you give up to easy. a well in alberta is like throwing money away.. any body want to buy mine, I will throw in free rust, hard water...