How to Convert a Septic to a Cistern

Have your septic tank pumped out and pressure-washed by a septic tank professional. Also, have all the septic system's pipes flushed, including the line from the house into the septic tank.

Fill the septic tank with water and add 5 gallons of bleach. Leave the bleach and water solution in the tank until the chlorine smell dissipates.

Locate the old sewer line from the house. Dig a trench as close as possible to the house and cut through the line. Install a 1/4-bend pipe onto the cut end of the line, using PVC glue according to the manufacturer's directions.

Add a section of PVC pipe to the 1/4-bend pipe, leading up to within a foot of the soil surface. At the top of the pipe, install a 12-by-12-inch catch basin with a grate. Cut a 12-inch-square piece of fiberglass window screen and press it into the bottom of the basin before installing the grate. This will keep debris and mosquitoes out of your cistern.

Clean all of the gutters and downspouts on the house thoroughly, using a trowel, scrub brush and garden hose. These will take rainwater directly into the converted septic tank.

Attach a 3-inch PVC connector to the bottom of each downspout. Then attach the connectors to a PVC pipe that leads to the catch basin.

Add a submersible pump to the new cistern. Plug it into a GFCI-protected outlet to avoid accidental electrocution while watering your garden.