Zeman Johnson Coffee Cooperative

Project Type

Project Summary

We are building a house on a coffee farm in the Dominican Republic with some unusual plumbing. The house has a circulating gray water loop system with treatment tanks, and it features a dry toilet with separate urinal. The dry waste will be composted (approximately) annually.

Project Description

The gray water system for this house collects water from some of the house sinks, the shower drain, and (optionally) the washing machine drain. These water streams flow through a small gravel bed where they combine with recirculating gray water. The mixed stream passes through wetland plants and a small tilapia tank to a collection sump.

The water is pumped uphill (four minutes each half hour in the day, and four minutes each hour at night) via a continuous loop in the house (no dead-end piping branches). Water in this loop is available to wash the car, wash laundry, clean muddy boots, water gardens, and rinse out dirty sinks. At the up-hill end of the pipe, there is a 100 gallon storage and pressure tank about 40 feet above the house floor elevation.

The uphill pressure tank overflows into a cascade of small water gardens on a hillside above the house, the end of the cascade drains back to the gravel bed where new gray water enters the system.

The gray water system will probably receive water faster than it is used. Excess gray water will eventually be directed to a larger tilapia pond to be located farther down-slope on the hillside.

The toilet system is modeled after some dry toilet systems of Scandanavia I read about, I modified a conventional toilet by breaking out the siphon loop and enlarging the bottom opening. I built a barrier across the center of the toilet so the front half of the bowl is a urinal, and the back half is open to the storage pit below.

The storage pit is a cement block room approximately 4 feet square and 9 feet tall. It has an expanded metal mesh panel placed diagonally in the lower section and is accessible by a metal door opposite the mesh panel (so solids falling from above tend to be deflected toward the door if they are soild enough, or just smear onto the mesh panel otherwise - think bug on windshield). The space below the mesh is fitted with a ventilation blower that discharges to a small odor-control biofilter outside the storage pit. The blower starts when the toilet lid is raised and stops when the lid is closed. The lid and seat of the toilet are gasketed to fit tightly to the toilet base.

The toilet has no water tank, but there is a urinal flush valve for the urinal part of the toilet. Urine and flush water accumulate in 55 gallon drums. When a drum is full and has 30 days of aging time thereafter, it is used to irrigate coffee plants on the hillside below the house.

The solid waste will be removed from the storage pit after a year and composted with banana leaves (many banana plants on this property also). The resulting finished compost will be spread among the coffee plants.

Updates