What is catchment?
Catchment is a water reuse strategy which involves collecting water, especially, the collection of rainfall ( also, called rainwater harvesting) over a natural drainage area such as roofs, gutters, drainage ditches…etc., for reuse. Greywater can be part of a water reuse strategy, but should be outside of the catchment process.
What is rainwater?
Rainwater is water that has fallen as rain, rather than water that has come from a a well, reservoir, stream, or municipal water source. Rainwater may be stored for future, but may require algae and pest controls (e.g. mosquitoes).
What is greywater?
Greywater is waste water from baths, sinks, washing machines, and other kitchen appliances, which is the relatively clean and may be reused for landscape waiting, if properly managed and or filtered. Greywater should be used immediately and not stored for future use.
Rainwater should be consider non-potable (not drinkable), unless it has been properly sanitized. This is especially true of runoff water, which have any number of pathogens along the way. Greywater is definitely non-potable nor should it be allowed to come in contact with the skin, nor is should animals and livestock be allowed to use it as a drinking water source.