Filtering of water for water tank storage
While all water tanks need to be sealed, to screen out mosquitoes, the lack of proper filtering or closed loop systems will create breeding grounds for mosquito larvae. An example of the screening process I with the Water Rhapsody Rain Runner, which filters harvested rainwater near the gutter, and this water may then enter an underground pipe to reach a remote rainwater tank.
If water is used for drinking, it should be filtered first. Filtration (such as reverse osmosis or ultra-filtration) will remove all pathogens. (Reverse osmosis is energy hungry) Other filtration consists of ozone and UV (ultra violet) treatment. Reports of illness associated with rainwater tanks are very infrequent, and public health studies anywhere have not identified a correlation. Rainwater is generally considered fit to drink if it smells, tastes and looks fine.
Certain paints and roofing materials may cause contamination. In particular, lead-based paints should never be used even as a primer onto metal surfaces. Tar-based coatings may affect the taste of the water. Chemically treated timbers and lead flashing should be excluded from roof catchments.
Maintenance of rainwater catchment areas includes regular removal of vegetation and debris from rain gutters. So long as a rainwater tank is kept closed to preclude light from entering, no algae will grow, so the only maintenance that needs to be done is perhaps removal of the sediment on the floor of the tank once a year.
Another imperative is that rainwater tanks should have a pre-filter under the eaves like the Water Rhapsody Rain Runner to prevent debris from entering the water tank/s and also to prevent any possibility of the feed pipe from a downpipe leading to the water tank (the ring main) from blocking. This pre-filter also prevents the ingress of mosquitos.
Apart from rooftops, tanks may also be set up to collect rainwater from concrete patios, driveways and other impervious surfaces. This water though may only be used for irrigation and toilet flushing, as it may be soiled from pedestrian and other animal use.