Greywater Irrigation: Cut Water Bills in Half While Growing a Lush Garden

Most households irrigate with drinking water, but plants thrive on gently used "greywater" from showers, baths, laundry, and sinks. The average U.S. home splits water use 50/50 indoor/outdoor; greywater recycling can nearly halve water bills. With historic droughts becoming the new normal, sending usable water down the drain makes no sense. Bonus benefits: lower carbon footprint (water treatment consumes massive energy), protected aquatic ecosystems, reduced sewage loads, and groundwater recharge.

System Philosophy

Greywater contains soap, hair, lint. Don't over-filter—use larger pipes/emitters and send water to garden as-is. Low-tech, dependable systems with minimal parts and no filters to maintain work best.

Setup Steps

1. Replumb greywater fixtures away from sewer to greywater system
2. Install greywater system
3. Install garden irrigation

Basic System Types

Laundry-to-Landscape

Easiest start. Washer's discharge pump moves water through ½-inch ball valves into mulch basins. No under-house plumbing changes.

Branched Drain

Gravity-flow for tubs, showers, sinks. No tanks, pumps, filters. Combined drains diverted outside, then subdivided into multiple branches to mulch basins. Requires downhill slope—may not work on flat lots or if irrigation area is above house.

Sump-Pump Systems

For uphill or distant irrigation. Greywater fixtures drain to basin with submersible pump activated by float switch. Distribution via ½-inch+ tubing to mulch basins (standard irrigation clogs).

Complex Systems

Multiple timed zones, computerized controllers, rain sensors, auto-backflush filters. Higher cost and maintenance.

Common Elements

• Diverter valve: Send greywater to sewer when needed (e.g., bleach in laundry). Remote actuator shown.
• Wood-chip mulch: Filters greywater, contains flows, spreads water horizontally via capillary action.
• Subsurface emitters: Nonpotable water can't use sprinklers; distribute underground or on ground under mulch.

Common Mistakes

• Watering lawns: Greywater incompatible with sprinklers; replace lawn with natives, use greywater for trees, shrubs, perennial vegetables.
• Storing greywater: Organic matter causes anaerobic bacteria and odors; apply immediately to soil.
• Overcomplicating: Pumps/filters = more breakdowns, maintenance. Use gravity when possible. Consider carbon footprint—elaborate systems may never offset water savings.

Key Questions Before Installing

• Pipe access below bathrooms? Second-story baths = invasive replumbing; slab-on-grade = impossible. Laundry system almost always doable.
• DIY? Laundry-to-landscape doable for handy homeowners (research + workshop). Others need pros.
• Plumber knowledge? Most don't understand greywater—violates "supply vs. waste" creed. Weird systems often from plumbers.
• Local installers? Western cities may have pros; elsewhere, look to permaculture community. Costs: $1,000+ (laundry), $2,000+ (branched drain), $4,000+ (pumped).
• Building codes? Check legality and permits. Many Western states easing restrictions; CA allows permit-free laundry systems with guidelines.

More info: Greywater Corps
Related: How to Harvest Your Rainwater
Resources: More ideas for saving water at home