Steve Williams, Atlanta

Southface is a nonprofit organization that for more than 30 years has promoted energy, water and resource efficient workplaces, homes and communities throughout the Southeast. In their new Eco Office a cistern was placed on the roof collecting water from a photovoltaic roof to supply water for their toilets, green roof irrigation and to cool the ac units to be more efficient. After several years of use I was asked to upgrade the system. The system worked, but the Rain Harvesting roof filter screen kept getting clogged from a mysterious gooey substance probably from pollution. There was also no easy access to the 1750 gallon plastic tank inside the wooden tank salvaged from a defunct winery. A three-way valve and float switch were added to allow automatic backup water for flushing if the tank runs dry.

To access the tank, a hole was cut in the cover and a hatch was made from a stop sign purchased from a salvage yard .

To fix the gooey screen problem a Graf Optimax filter was placed in the tank after the first flush filter to screen the debris and mosquitos.

After about 1.5 years the Graf filter was replaced with an Intewa WSP-100. The reason is the Graf with its fine screen was losing efficiency, because of a film building up after rain events. The film is clear and even with an enlarged first flush the substance was getting through. The Intewa filter uses a weir screen filter which allows more water through. The Intewa filter is tied into a calming inlet which inhibits the water entering the tank from stirring up any sediment on the bottom. To the left is the float switch hanging just above the bottom of the tank to tell the three-way valve when the tank is empty.

Here you get the master article

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