Stan, all you're talking about is grey water? Not black water? Just the sink, bathtub, shower, washing machine?
Not sure where you are, but since you're asking here, and not the building department where you are, this is not a permit issue? I'm assuming you want to have this water "cleaned up" before you use it in a garden?
Assuming you will be using soap, hopefully not detergent, bar soap, dish soap, the first tank could be half filled with bark chips and
compost and worms, and then the overflow can go into a bark chip trench in the ground via PVC Lines. Some people send it straight into bark chip trenches, which then will seep through the soil to a tree/landscape planting (not food production) of your choice that is downhill from those bark chip trenches.
There is a black water version of this bark chip/compost/ worms mix with about 5,000 worms per 500 gallon tank. The worms work it over, it overflows into a second tank with plants or ground trench with bark chips and used for landscape.
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There are reed beds you could run it into straight from the house. I designed mine on this picture, using pond plants, and it works really well. We do not have a frozen winter, so the reed beds are open. But there are municipalities in Canada that use reed beds, and those must freeze, so you can search on those.
https://permies.com/t/39474/Grey-water-reed-bed-system
Mediterranean climate, hugel trenches, fabulous clay soil high in nutrients, self-watering containers with hugel layers, keyhole composting with low hugel raised beds, thick Back to Eden Wood chips mulch (distinguished from Bark chips), using as many native plants as possible....all drought tolerant.