Save money and recycle on rainwater tanks

Here is my rainwater collection system that uses food grade recycled 55 gallon drums. The big poly tanks can be very expensive and are hard to arrange in a linear fashion. 55 gallon drums have a coarse and fine thread bung. The fine thread is npt 2 inch and the adapters can be got on Amazon for the coarse thread. Apply silicone thoroughly when plumbing the bungs. A little screened bleeder hole will need to be made in the barrel tops to equalize the pressure. I think the barrels cost 90 dollars total plus 100 dollars of fittings.

Looking good. That system will be easy to expand as you get more barrels. Is that one on the "second story" hooked up? How do you keep water from coming out the bleed vents in the bottom row?

The use of individual drums is great when you cannot collect enough cash to purchase a large tank up front.
They can be added too as and when possible.
In Australia tank prices and volume are :
barrels  gallons       $US.          litres.    $A
5               275.         450          1100.      690
10.            550.          900         2200.      1190
100.          5500.        9000      22000    2600    
So you can see the benefit of the larger system if its possible.
There are also great savings with less fittings.

Sometimes the solid pipe fittings between the barrels break if there is any movement.
Also the larger tank volum allows settlement and water cleaning by nature itself. no chemicals or filters.

That is my "first flush" diverter. People disagree on if they are even useful but it catches the first 30 gallons or so off the roof before the tanks begin to fill. After the rain I dump it. Most of the dust and pollen off the roof surface is washed off by this first 30 gallons. Otherwise I just use a carbon filter on water I drink.

I have found with the 20,000L tank I dont need carbon filters, since it self cleans itself with time.

We have been off grid since buying the plot in 1974.  Our 20,000 gal concrete tanks installed in 1986 have virtually no sediment on the bottom.  Each of our first pass diverters uses about 20 litres (4 gal) X 8 diverters.  Each down pipe has two filters before the water gets to the diverter.  You can make your own with a 10 mm grid wire and a fine kitchen seive set into a tapered pipe.  Our down pipes are 90 mm, with 1400 mm diverter collectors.
I used both these products :  
This is DIY version which is well put together in my opinion:  

Thank you for the links. I think it's intresting that most of the legit sources I have seen concerning rainwater collection are from Australia. I guess there is a lot of rainwater collection there? I live in a very wet and rainy area so my tank capacity can be tiny. I just do rainwater because wells are expensive and the well water here sucks.

Wills, Australia is a dry country.
So is Israel, but maybe they have even less rainfall, but they have great skills with drip watering sysyems.
A water test would be a great idea when you get to it!