Rainwater harvesting/Rainwater harvesting system/Rainwater prefiltration

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Prefiltration is the act of diverting and preventing the entrance of medium to large sized debris into the storage unit of a rainwater harvesting system. Simple in concept, many different manufacturers have developed prefiltration devices, utilizing the unique properties and behavior of water flow to be filtered at reduced maintenance or under greater flow conditions.

Types of Pre-filters[edit | edit source]

Vortex Pre-Filters[edit | edit source]

One kind of pre-filter, known as vortex pre-filters, use the high velocity of water entering the filter to filter debris out of the system, thereby forcing the water through the side of the filter. The remaining water and debris are then swept out the bottom to stormwater management system.

Intewa Purain Prefilter

Downspout Pre-Filters[edit | edit source]

The downspout pre-filter is placed directly vertically in the drain or gutter and has a mesh screen placed at an angle (usually 45 degrees) to filter out medium to large sized debris from the water. This kind of pre-filter is susceptible to getting clogged and if the mesh screen is not cleaned out, then no water will be able to pass through the pre-filter.

Basket Pre-Filters[edit | edit source]

Sometimes buried directly, other time located in a concrete vault next to or on top of the tank or cistern, a basket pre-filter functions on a simple open top cylinder shaped filter. If any rainwater that cannot through or if the filter is clogged, the excess flows out the overflow to the stormwater management system.

Hydraulic Jump Pre-Filters[edit | edit source]

The hydraulic jump pre-filter utilizes the same self-cleaning methods of the vortex pre-filter but within a simpler design. When a high enough flow has been reached inside the pre-filter, the water begins to cycle within the pre-filter and cleans the built-in filter, thereby washing the debris out to the stormwater management system.