When a smaller surge tank or larger first-flush device is required to fill a taller main tank, the smaller pipe in the center is necessary to allow the water to flow back up to fill the inlet on the right. Thinking through a problem will usually lead to several possible answers.
Ferro-cement tanks are built on site and materials can be carried to remote locations. Successful results are ensured by careful screening of installer's experience and qualifications. Failures have happened, as in this case!
I have consulted on rainwater systems from 500 gallons to over 100,000 gallons. There is no best way to harvest and there is no best tank. Everything depends on your particular needs and site. I don't start talking tanks until we have spent about an hour walking the property, checking the roof, discussing preferred cistern locations, etc. The tank is the last thing we consider. I have created a little free sub-site on Wix.com. It allows me to have a few more image examples without using the bandwidth on this main site. Look around, but remember to come back to this home site! http://dickpeterson.wix.com/consulting
Rainwater Harvesting Consultant
This 24,000 gallon CorGal tank supplements well water for potable use at a Medina Ranch. Metal cisterns require a thick, porous "sock" against the inside of the metal to avoid condensation on the tank. A food-grade vinly liner inside the sock actually holds the water.
When access to the carport is tight, we can use oblong tanks to replace less expensive round ones, giving us extra space. Cordwood storage for this historic log home will disguise the tanks at the end of the porch.
Sometimes we can overlook the most obvious places to install a tank. In this case we used wasted space under a deck to place a City of Austin REQUIRED 2,000 gallon tank by using a custom Original Rainwater Pillow.