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 .
An Intewa WSP-100. was used, because of the screens of other German filters need occasional cleaning 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.
The water is pulled from the tank through the floating filter which was added to retrieve the cleanest water just below the surface.
When the tank runs dry the three-way valve automatically switches to municipal water until the rain comes to fill the tank. The UV and sediment filters were upgraded and moved to provide easier access for maintenance.
The water outlet is the right pipe wrapped in heat tape to prevent freezing. A drain was added to the left to empty the tank when service is needed. It is tied in to the overflow shown below left.
Directly below the drain pipe is Raintube used to diffuse the water that leaves the tank.