Collection of Residential Shower and Bathtub

Gray Water for Reuse to Flush Toilets

and for IrrigationAn Experimental Project

Kenneth Garges

Gray Water

• Collected from bathtub and shower drains.

• NOT potable.

• Quickly fouls if stored.

• Fresh gray water can be used for subsurface irrigation but not sprayed.

• Not pure enough for toilets.

Filtering Gray Water

• Commercial systems are very expensive.

• Example: Flowtender price $3840 - $18,968

A New Simpler System• Collection in recycled 55 gallon drums.

• Spun polypropylene mesh pre-filter.

• Slow sand (aka biosand) filter modeled after Center for Affordable Water and Sanitation Technology (CAWST), a non-profit delivering water treatment systems to developing countries.

• Pump controlled by Arduino to keep storage brief by draining stale gray water.

Current Project Status• Collection tank plumbed to shower drains

• Filtration tank completed, running for 20 days (CAWST recommends at least 30 before using filtered water)

• Filtered water storage tank completed but not plumbed to building toilets

• Controller hardware finished

• Software still in progress

Cost and Benefit

• Total hardware cost ~$950.

• Mostly Home Depot, Granite Rock, eBay.

• Currently collecting 40-70 gallons/day.

• Purity of filtered water not yet tested but looks promising.

• Similar to systems in developing countries.

• Current city regulations may need revision.