our first catchment using puropse made parts.

This is a system we installed for a friend. We get 40 plus inches of precipitation, distributed evenly throughout the year, but are locked out of harvest half the year due to low temperatures.

We were able to re-pitch about a hundred feet of gutter fed from 900 sq' of roof and divert to catchment via one convienient downspout and another 200sq' from another.

It fills its 1200 gallon reservoir fast with 1-3/4" of heavy rain!

There are some things we learned along the way. And the next one will be even better. This one had to have its plumbing in a compact space which was challenging as far as layout. There are some things that may improve winterization, id like sunlight resistant poly or nsf pvc conveyance to the system, and a high capacity filter for incoming water. A giant Berkey would be perfect, but i doubt economics would be practical and so post filtration for this system is in the works.

If using gravity feed, use full flow fittings and hose bibs. Harder to find but a big advantage. These were at Lowes, quarter turn!

https://m.lowes.com/pl/Sillcocks-hose-bibbs-Valves-valve-repair-Plumbing/2056014184

What will they be using the water for?
If bigger tanks were set up, the cost of installation per Gallon of water will drop substantially. Is that possible?
We use minimum 5000 gal tanks here.

The rainwater is to be used for watering garden and trees and during drought. The garden water will be filtered as she does harvest from composit roofing.  

It also passes through a whole house filter (soon to be R.O. purified) on its gravity fed waterway to a 50 gallon reservoir in the basement for microgreens and plant starts in an led lit vertical garden.