This site explains water catchment and has some great suggestions on how to accomplish this. For a example there is a Mexican created product called a Tlaloque that helps separate the rain to keep from the first fall (dirty) from the clean rain.
I have emailed them in regards to our system at our home. If any of you are catching rain water you may be interested in this system.
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Re: Rain water catchment
Posted by Monte Morgan on August 3, 2018, 12:38 pm, in reply to "Rain water catchment"
The Tlaloque concept is a system that has been in use in South America for many many years. Local plumbing materials from the ferreteria along with a floating ball are all one needs to build one of these first flush systems. There are other designs that achieve the same results. Our friend google gives us lots of examples at:
Experience in rainwater harvesting system shows that A. although you may have a large cistern for storing rainwater it is almost never enough in a domestic situation, B. If the intent is to use rainwater for landscaping or gardening, the best place to store water is infused into the ground. C. If the intent is to use the rainwater as a potable water source, additional purification needs to be integral to the system. D. A metal roof is the preferential collecting surface as if it is without texture, it will wash cleaner faster.