Septic systems are common in rural areas or areas without connection to municipal waste treatment. Homes with poor drainage or rocky soils may require a sand filter septic system. Sand filter systems use a contained area filled with sand as one step in the biological treatment of septic effluent. Wastewater is pumped to the sand filter for intermediate treatment, and then pumped to a distribution field for final dispersal.
Fix locations for the septic tank, pump box, sand tank, second pump box and distribution field in that order. The distribution field should be at the same or lower level from the sand tank. Local plumbing codes may dictate setback distances for the tanks, or the distribution field used for final effluent disposal.
Consult professional service companies for local codes, excavation, plumbing and electrical contracting as needed to safely complete this installation. Your local code jurisdictions may require multiple permits for septic installations, so consult with them before starting this project.
The components of a sand filter septic system include a septic tank, a pump tank with submersible pump, a sand filter tank, a second pump tank and a distribution or drainage field.
Connect the home waste plumbing to the septic tank with 4-inch plastic pipe. Most newer sewage systems are plastic, so plastic pipe cement can be used to connect the new piping to the old. Use plastic pipe connectors and adapters to mate the home piping to the new septic system piping. If the old sewer pipe from the home is metal, use a metal-to-plastic transition piece. Dig a hole and place the septic tank in the hole below ground level. Install a septic tank access port above grade using a concrete lid. Place the first pump tank in the same hole as the septic tank, at a level where the septic tank outlet will drain by gravity into the first pump tank. Connect the septic tank outlet to the first pump tank with four-inch plastic pipe.
Install the lift pump in the pump tank by placing it in the bottom of the pump tank. Run electrical wire to the pump and connect it per the manufacturer's instructions. Add high- and low-level float switches to operate the pump per the manufacturer's instructions. The low-level float should be placed above the pump so the pump shuts off before it runs dry. The high-level float switch should be placed above the low-level float switch so it turns the pump on before the liquid level reaches the top of the tank. Install a separate high-level alarm float switch on a separate electrical circuit with an audible alarm inside the building. The high-level alarm will sound if the pump quits for any reason and the tank fills up. Use a nylon rope and a quick-connect union on the pump outlet to allow easy removal of the pump for maintenance and replacement. Install an inspection port or cover on the pump tank.
Place the sand filter tank on the ground downstream of the first pump tank. Place a four-inch drain perforated drain pipe at the bottom of the sand tank. Add several inches of gravel and level the gravel layer. Add one or two four-inch inspection pipes into the gravel layer using a length higher than the top of the sand tank so you can look into the sand tank . Cover the gravel with filter cloth. Add sand to one foot below the top of the sand tank. Install inspection pipes randomly in the sand level so the sand can be inspected in the future. Place perforated distribution pipe in runs three feet apart on top of the sand, and connect them to the pump tank discharge. Glue all plastic piping with plastic pipe cement after dry-fitting the pipe to confirm placement. Connect the pump outlet to the distribution piping using plastic pipe. Add six inches of gravel, filter cloth and a top layer of soil. Mound the soil so it is higher in the middle of the tank; you want rainwater to run off, not absorb into the sand tank. Do not install a plastic liner above the sand tank, as oxygen is needed for the sand tank to purify wastewater.
Dig a hole on the downstream side of the sand tank for the second pump tank. Put the second pump tank in the hole so the top is at ground level. Connect the second pump tank to the outlet of the sand tank using four-inch plastic pipe and pipe cement to connect the two tanks.. Install the second lift pump, electrical wiring, float switches and float switch alarm as in the first pump tank. Install an inspection port or cover on the pump tank. Follow the pump manufacturer's instructions for proper wiring and float alarm placement for both pumps.
Install the distribution field one-inch perforated piping in trenches at least three feet apart. Dry fit the plastic pipe together and then use plastic pipe cement to connect all piping. Local codes may require use of sand or gravel in the field around the distribution piping. Check your local building code office for septic system regulations. Cover the distribution piping with filter cloth.
Perform a system inspection when the system is put into service. Run water in the home and confirm the first pump tank turns on. After it pumps, the effluent will filter through the sand tank and drain to the second pump tank. Ensure that effluent is draining to the second pump tank and the second pump runs properly. Check that the effluent being pumped from the second pump tank is distributed evenly through the distribution field. If all connections are tight and all parts of the system are working correctly, back fill all holes and the distribution field with dirt removed in earlier digging. Landscaping or grass may be added to the back filled areas as desired.
Things You'll Need
Concrete sand tank or treated wood and vinyl sheet
Four-inch plastic pipe
Two pump tanks
Two lift pumps with on/off level float switches
Two high level alarm float switches
Two plastic pipe unions sized for the pump discharge
One-inch perforated piping
Plastic pipe fittings
Sand tank systems require periodic inspection and maintenance. Check that the lift pumps are operating with the float switches. Test the high-level float alarms. Inspect the sand tank using the inspection pipes. If water is filling up the sand tank the tank will need to be opened and the sand replaced. Expect to replace the sand tank contents every three to five years.
Sand filter septic systems can provide years of excellent waste handling for homes or businesses. Routine inspection and maintenance of the septic tank and sand filter will permit these systems to work optimally and result in minimal environmental impact. A sand filter provides excellent waste filtration and will extend the useful life of a conventional septic system.