We originally designed for each tank to be interconnected in the overflow system much like they are connected down below for water equalization. However, we realized that only the tanks with inlets needed to be overflowed, so we saved some pipe. Our original design allowed for a back up to the water equalization system in the event that the bottom interconnections couldn't keep up - the water would've been able to travel to other tanks via the overflow system (and lastly, to the outside). But we figured this wouldn't happen often enough to justify the cost and messiness. Also, interconnecting all tanks via the overflow removes the ability to completely remove a tank from service. If a tank to which overflow is routed gets a leak, overflow water will continue to be sent underneath the tank complex rather than to where overflow water is supposed to go - out in the pasture.
Our first idea for overflow water was to make a little pond. My skepticism that we'd actually have enough water to make it worth it, plus our worry about standing water with the kids around changed our minds. Now the overflow will go directly out to the pasture and the slope of the land will carry it down and hopefully we'll have a nice tidy little irrigation system. If it turns out that we have so much overflow that the pasture is soggy or something, we'll deal with that luxurious problem when it comes. We use these caps to prevent critters from entering the overflow pipes.
All tanks except the truck tank are interconnected via a 2" pipes for an airvent system. There are three snorkels for the rain tanks to share and the truck tank has its own snorkel. We decided on using only 2" diameter pipes for the air vents because air can move much faster than water. We figured that the ten 2" outlets will allow air to move out faster than the three 6" inlets will allow water in. We capped the snorkels with these little gnome huts that will keep debris and mosquitos out.
|Pick up pipes (4 hrs)||$160|
|Riser pipe adapter installation (12 hrs)||$800|
|Order and pickup 3" pipe (5 hrs)||$175|
|Fill in gravel, layout pipes for vents (8 hrs)||$652|
|Put together 2" vents (10 hrs)||$400|
|Overflow connections (8.5 hrs)||$680|
|4" tank adapters, gaskets, and fittings||$2736|
|4" pipe adapters and fittings||$1339|