How to Build a Concrete Cistern
- 1). Locate a suitable water collection location. Cisterns work best when placed right next to the building that will use their water and beneath a large, smooth roof. Roofs of smooth material collect the least debris that might flow into the water. Find a roof side that faces away from sources of contamination such as a highway or a pesticide-treated orchard.
- 2). Excavate the ground to build a rectangular bed for the cistern, either using a back hoe or by hiring an excavator, and make sure the hole remains even with the ground on all sides. An average-sized cistern for a family of 2 is 8-feet deep by 8-feet wide by 12-feet long.
- 3). Build a form for the concrete floor out of 2 by 4 planks, constructing a rectangular framework. On the outside of the framework, drive 2 by 4 planks into the ground as stakes at 2-foot intervals and nail the stakes to the framework from the inside of the framework with the hammer. These stakes form the foundation of the concrete form that you are going to use to mold the concrete in later steps.
- 4). Cut the concrete reinforcing mesh with the wire cutters to fit the dimensions of the wooden framework.
- 5). Pour concrete into the framework, bringing in a ready-mix concrete truck hired from a local company with an experienced operator. After pouring about a 2-inch depth of the concrete floor, insert the concrete-reinforcing mesh and continue to pour another 2 inches for a total depth of 4 inches.
- 6). Remove as much of the wooden framework as possible after the concrete floor hardens. Some wood will have to become sacrificed to the structure and remain in place.
- 7). Build a rebar support grid for the concrete walls using #6 rebar. Space the bars of the grid at 1-foot intervals to leave 1-foot-square spaces and wrap 16-gauge wire around the connections in the tight coils to hold the grid in place.
- 8). Drill holes into the concrete floor around the edge to give the ends of the rebar frames a place to sit. Before drilling, set each rebar piece in position where it will stand out of the floor and mark where the rebar ends touch the floor. This allows you to mark the holes before doing any drilling. These don't have to be evenly spaced, but adding rebar every 6 inches strengthens the structure considerably. Use a hammer drill and do not drill all the way through the concrete floor.
- 9). Set the rebar walls into the holes and bend more rebar at 90-degree angles. Put these angled bars in the corners as support and wrap wire to affix them to the rebar walls, connecting all of the rebar support together.
- 10
Build wood walls around the rebar with 2 x 4 planks to create forms for the concrete walls. - 11
Pour concrete into the wall forms and allow the concrete time to dry. Remove the wood forms. - 12
Build a wooden frame for the lid of the cistern with 2 x 4 planks, and leave an open hole for a hatch through which to access the cistern. The hatch should allow a human to fit through for cistern cleaning and maintenance. - 13
Pour concrete into the lid of the cistern and allow to dry. - 14
Cover the hatch fully with a heavy block or plate.