Ferrocement Rainwater Cistern

The first few years, they conserved cash by using a rainwater cistern for water rather than having a well drilled. They stored the rainwater from the roof in a ferrocement storage tank in the crawl space.

Sections of #3 (3/8") rebar were bent and wired together into a frame. 

Behind the rebar are the holes leading to the manifold for the rock storage under the floor of the one-story north section of the house. The rock storage was never used because the solar roof was not generating sufficient heat due to the cloudy winter skies in northern Illinois.

Metal lathe was wired to each side of the rebar frame. Mortar was pressed into the space between the two sheets of lathe and also plastered on the outer face of each sheet.

The ferrocement storage tank was divided into two sections so that one section at a time could be drained for cleaning or repairs. PVC drains can be seen at the lower left.

Cementitious waterproofing was applied to the inside of the tank.

A pair of smaller capacity tanks were built. Each had a coat of cementitious waterproofing applied to the inside of the tank. One was filled with sand and performed well as a filter (The PVC pipe at the bottom of the tank on the right is the outlet.)

The other tank was simply filled with water and covered with a tarp to see how long it would hold water. After 10 years, it was still almost full. A small amount had evaporated, but there were no leaks.

The water storage increased the amount of mass inside the thermal envelope to help save energy by moderating temperature swings. The first floor of the two-story section had a tile floor on top of 2" of concrete, and the walls and ceilings had a double layer of 1/2" drywall.

Rainwater was pumped from the large storage tank into the sand filter. After passing through the sand filter, it emerged at the bottom and drained by gravity into a 250-gallon plastic storage tank below it. A chlorinator added chlorine to the filtered water in the plastic tank. A pump and pressure tank provided water to the house once it was weathered-in and insulated.

An Illinois state park had utilized a similar rainwater system for providing potable water at a campground facility.

But this was the first rainwater system approved by the State of Illinois for use in providing potable water in a private residence. 

Getting Health Department approval was an adventure. The fact that a similar system had previously been approved at a state facility helped a lot. It's always better if you can propose using a system that has a history of working somewhere else, a principal which is at the core of "It's a Tribal Thing!"