collection of residential shower and bathtub gray water for reuse to flush toilets and for...

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.