If I lived there in the desert I would use all the water, grey and black
for irrigation and fertilizer. Plants
will love it.

In Tucson AZ, during construction, I ran the drain line for my washing
machine to the ABS and ran it out beneath the soil outside rather than into
the sewer (septic) system. The washer put out 100 gallons of water on
laundry day..once a week.I ran the pipe down a short grade outside in the
yard to where I buried a ~30 gallon plastic pail ( originally for 3" pool
pucks). I ran two 1/2" blk vinyl drip water lines out of the bottom/side of
the pail and circled the 1/2 acre front yard where there were native
Mesquite and Acacia trees..probably 15-20 of them. I also ran some 1/4"
dripline to a large Ocotillo and a couple of Fan-Tex ash trees I had
planted.

The trees loved the stuff..didnt care about the soap..had the best looking
yard in the neighborhood and FREE drip water.
BTW, no lawn, all aggregate paths & rocks with a couple of bridges over
small washes.