Start with a plastic tub

Add polyester batting

Coarse gravel layer

Fine gravel layer

EWEB filter sand

finish with river rock

Filter Construction Procedures

Ingredients

5 gallon plastic tub (with drainage holes drilled in bottom) is filled with the following layers of materials:

• 1"- 100% polyester fiber
• 2"- 3/8" round rock
• 3"- 3/4" round rock
• 3"- filter sand (uniform grain size about 0.5mm)
• 1"- 1 1/2" round rock

Preparation

• Flush system using Millrace water until effluent clarity is indistinguishable from incoming water. This process (about 2 hours) helps to encourage the development of a "schmutzdecke" (a layer of biological slime that aids in trapping small particles.)
• Filter is elevated and slightly tilted to encourage water flow and catchment.

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Rainwater Harvesting is a Vital Signs Case Study
prepared by Angela Matt and Joshua Cohen, Spring 2001.