(i) Catchment’s Subsystem

The rooftop is the catchments subsystem. For non-potable use, any roofing material can be used as the catchments subsystem. As for potable use, the best roof materials are metal, clay, and cement materials although all roof material types have been used (except asbestos). The roof material used in the study is of cement tiles.

Catchments subsystem depends on the roof configuration of the house. In this study, due to the typical roof design, only the front section of the house is considered. The total roof area is 60 m.

(ii) Conveyance Subsystem

The function of this subsystem is to convey the rainwater from the catchments sub-system (rooftop) to the storage tanks. Basically this subsystem consists of 3 main components. These components are the gutter, downpipes and the conveyance pipes. Rainwater from the rooftop is channeled to the gutters (6" or 150mm) and then through the downpipes and finally through the conveyance pipes to the storage tanks.

Aluminum and galvanized iron are usually the best materials for the gutter due to its good corrosion resistance property. For the conveyance pipes, usually UPVC pipes are used. However in this study, UPVC type materials were used as gutter and conveyance pipe due to their flexibility during installation. The gutter slopes at 6 mm. per meter and gutter hangars are provided at 1 m center to center.

At the downpipe inlet a net should be placed. The net is to trap rubbish, leaves and other debris usually found on rooftops. Sharp bends along the run of the gutters should be avoided. This is because, rubbish usually gets stuck at corners and therefore this would affect the flow of the rainwater.

(iii) Filtration

Rainwater from the rooftop (the first 1 mm of rain) is usually contaminated with dirt, bird droppings, leaves and other materials. The first flush (60 gal. or 276 litres) of rainwater from the roof surface is directed into the first flush tank of 200 litres (see figure below) to filter out these materials from the rainwater before it is stored in the storage tanks.

(iv) Storage Tank

(v) Booster pump

A 1.0 horsepower pump (see figure below) with minimum head of 12 m was installed to pump water from the storage tanks to the roof tank (250 litres).

(vi) Roof tank

Additional roof tank (250 litres) were installed on the roof in addition to the existing domestic roof tank. The additional tank provide separate rainwater supply for non-potable household use.

(vii) Plumbing to toilets, washing machine and general use

The study house also has a separate plumbing system to cater for rainwater usage. Since rainwater was for non-potable use, the plumbing system was installed in such a way that there will be a bypass connection for each flushing cistern. In case of water shortage or non-availability of rainwater, the public water supply can be always be switched on. The rainwater plumbing system also connects to the washing machine pipe and pipe for general cleaning.