[conradpdx]

One of the main things you'll need to consider is purging the tanks on a regular basis. I know that some building codes now allow gray water systems but most require the holding tanks be emptied every 24-48 hours. I believe they ask this to help keeping the mosquito population down and because the water will get rancid with all the little dirty bits.

Now honestly most the systems being used on residential housing are typically "illegal" or not to code. So do you what will. but if you plan on selling anytime soon make sure you can hook the old system back up.

Now with washing machines unless you have diapers or other items that frequently have fecal matter on them you can use this water directly on plants and lawn. You can even get away with "non-green" detergents. The plants love the phosphorous that is contained in standard detergents. The reason your local municipality doesn't like them is that it will get into the local water source and feed the algae which will choke out the rest of the life in the river/lake/ whatever.

There is lots of info out there on gray water. Most importantly you need to make sure that all pipes and tanks are labeled boldly as non-potable water.

edit PDF too big for attaching here will find link to pdf and post it here.

Sorry PDF is the state of California guide for using gray water for landscaping, with no mentioning of use in toilets.