Graywater

Graywater is the wastewater a home makes from washing, not from toilets or the kitchen. It comes from clothes washers, bathtubs, showers, and bathroom sinks. It does not include water from toilets, kitchen sinks, or dishwashers. Those carry grease and food and count as blackwater. Caught separately, graywater can water a yard instead of going to the sewer or septic system.

In Arizona, graywater reuse is run by the Department of Environmental Quality (ADEQ). A typical home falls under the Type 1 Reclaimed Water General Permit for graywater. It covers home systems that make less than 400 gallons per day. The permit is automatic if you follow its rules. You file no application and pay no fee as long as you comply. The rules say to use the water only on your own lot, apply it by drip or flood and never by spray, keep it below the surface or covered, and store it no more than about 24 hours.

For example, a homeowner in Cave Creek can route the laundry and shower drains to a drip line that feeds desert trees, reusing hundreds of gallons a week. In Arizona's dry climate, that reuse stretches a scarce resource and keeps yard plants alive through summer. It also draws less from the well or city supply. Larger flows, between 400 and 3,000 gallons per day, move up to a Type 3 permit.

Graywater is not the same as rainwater harvesting, which catches roof runoff. It is also not treated effluent from a plant. Graywater is your own lightly used indoor water, reused on site. Planning for it early, when you lay out plumbing on a build-on-your-lot project, is far cheaper than adding separate drain lines later.