It doesn't seem reasonable to be spending so much money on all of the fitting I see involved both in the above postings.....and also in the suggested video.
All that is needed is one tank with fittings and then siphon lines from one tank to other tanks.
One inch black poly works well. 3/4, 1/2 or even old sections of garden hose would work well too. I store about 5,000 gallons this way but I do have two tanks not in the siphon system. One is 1,100 gal and the other is 1,000.
To get water from the siphon system you can have a faucet on the bottom of the main tank for low pressure water.
To get pressure water I siphon from the main tank to a 55 gallon barrel and then pump with a small sump pump.
The 55 gallon is also convenient for mixing urine into the irrigation water. I have a tee at the top of a 5ft. piece of 3/4 pvc and one end directs back into the 55gal with a valve and a nozzle for jet agitation.