Large cement cisterns are used to capture water, or create septic systems.
A cistern is a large cement tank poured to create a basin for water, or other liquids. Cisterns are typically built to catch and hold rainwater for use at a later time. Cisterns are different from wells in that they have a waterproof linings, and do not have their own water source. Linings are manufactured from preformed plastic, or created by covering the interior surface of the cistern with a thin coating of lime plaster. Does this Spark an idea?
Instructions
Excavating the Hole
1. Excavate a hole in the ground larger than your planned cistern. The bottom of the cistern hole should be undisturbed ground, so dig the last 6 to 12 inches by hand, not with excavating equipment.
2. Build a concrete form out of 2 inch-by-6 inch scrap grade lumber. For our example, we will discuss an 8 foot-by-8 foot square cistern that is 6 feet tall. Build a square frame, and set the frame into the hole so that it rests securely on the bottom of the hole. Make sure the top edge of the form is level all the way around. The cement is leveled to this wood form.
3. Push the U-shaped pieces of rebar into the ground, so that the bottom of the "U" points upward. Position these steel reinforcing rods around the perimeter of the cement floor so that they extend upward 3 to 4 inches higher than the concrete forms that frame the 6-inch thick floor.
Pouring the Floor
4. Pour the premixed concrete into the concrete form. Pour enough concrete to completely fill the form. The entire structure must be poured in one step so there are no seams in the floor.
5. Smooth out the surface of the concrete with a cement finishing towel. Push the concrete out to the edges of the form, and make sure no voids exist between the form and the wet concrete.
6. Float the surface of the cement with a cement float. Smooth the concrete out until the entire surface looks smooth and wet. Allow the floor to dry according to supplier's instructions before proceeding.
Pouring the Walls
7. Build the form out of 3/4-inch CDX plywood and scrap-grade dimensional lumber. You will create a 6-foot-tall, open-bottomed box standing on top of the poured floor. Build another identical box which is just 12 inches larger in width and depth around the outside of the first. This will create a 6 inch wide hollow cavity which sets on top of the cement floor. The cement walls are poured into this cavity.
8. Make sure the wall forms are centered over the rebars, which stick up through the concrete around the perimeter of the floor. When the concrete is poured into the cavity between the inner and outer wall form, the concrete walls will harden over these reinforcing rods. This is essential to mechanically fasten the floor and the walls together.
9. Pour the concrete into the forms, and trowel off the tops of the walls in the same way you trowel finished the floor. Allow the cement to dry according to the supplier's instructions.
10. Remove and discard the plywood and framing lumber. Push the excavated dirt back into the hole around the new cistern with the shovels, or the excavating equipment. The dirt will settle a bit, so mound the dirt up 8 to 12 inches around the perimeter of the cistern. Now the cistern is ready for a top, or for the installation of a rain collection system.
Tags: around perimeter, according supplier, according supplier instructions, cement floor, cistern with