I think it’s pretty clear what the concept here is.  Who doesn’t love the idea of washing your clothes and then using the soapy, dirty water to flush your toilets?  Not me.

Advantages: space savings, grey-water re-use, nice environmental feeling while flushing.

Disadvantages: the occasional dropped sock, and perhaps a bit of a bumpy ride if you can’t wait to sit down and go until after the spin cycle.

(from unplggd.com)