I've discovered on multiple off-grid homesteads that with any serious gardening going on, the need of water for irrigation is at least ten times more than all other household uses combined; unless perhaps you are in a quite rainy climate. (This was assuming no flush toilets in use, only showers, laundry, and kitchen) So as far as total water conservation is concerned, yes, greywater is valuable, but perhaps not as valuable as many think it to be. It's definitely not worth a lot of elaborate re-plumbing and re-working. What I've done most places is what Art Ludwig calls a drain to mulch basin....run a wide hose....1 1/4 inch black irrigation plastic works well, direct from each drain outside at a downward slope the whole way to a dedicated pit filled with wood chips or other coarse mulch, and then plant moisture loving plants, usually perennials through shrubs to trees, all around and in it. In temperate climates things like elderberry, blackberry, comfrey, etc. In dry climates just about any kind of useful tree or shrub can benefit. If the single source is very large, say in a large family or community situation, then you might need a branched drain or something like that, some way to spread the water out. You don't want any standing, because mosquitoes, and you don't want it to clog.....I've often found that setting up some kind of sump pit at the end of the drain hose....a kind of buried bottomless pot or some such so the water comes out into empty space and drops into the mulch, rather than directly into it. Earthworms and rodents and all will churn up that mulch and mix it with soil eventually....and this is moreso in dry climates since those things are attracted to the moisture. In California I actually had to dig it out and put it in garden beds every year or two and place fresh mulch for this reason, whereas in wetter climate the basins seem to maintain for years.