Filter plays vital role in Rainwater Harvesting. Primary job is to keep organic particles and silt out of the rainwater to be harvested. The filtering process should not result in loss of rainwater to be collected or should not also result in choking and consequent flooding.
For individual homes, a simple drum with a cloth covered inlet is good enough. Passing the rainwater through a sand bed is simple and easy. For a 100 square metre roof area, one 60-litre drum filter is usually enough. There filiter available are many in the market and most of them do the basic job of keeping organic particles out. Go for the simpler and easy to maintain and to clean.They should also be cheap and easy to replace.
A bye-pass system helps in the filtration process because it is only the first 5 mm of rain which usually needs to be cleaned. The filter, if made of ferro-cement, can last longer and is much tougher than plastic. Ferro-cement does not crack in the sun and is much more eco-friendly than PVC. Before buying and installing a filter, ask what it does, the difference between input and output water quality and how easy is it to maintain.
Since a filter has to handle a heavy downpour at times it cannot function at micro-filtering the rain. It can only keep the larger particles free.The filtering process should not result in loss of rainwater to be collected. The entire rainwater harvesting system consists of a catchment, which is usually the roof, the conveyance, which are rainwater gutters and downpipes, the filters and finally the storage or recharge, which is a sump or a well.
