Understanding A Sand Filter System

• Why a Sand Filter System?
• The Septic Tank
• The Pump Chamber
• The Sand Filter
• The Chlorinator
• Additional Information

Why a Sand Filter System?

Septic tanks with gravity flow leachfields have been used for many years in areas not served by public sewers. Unfortunately, not all soil and site conditions are well suited for these conventional systems. To protect public health and water quality, alternative systems are often used in areas where conventional systems cannot assure safe sewage treatment. The intermittent sand filter is one alternative, which:

• Can be constructed above or below the ground.
• Provides a high level of wastewater treatment.

The following information will help you understand your sand filter system, and keep it operating safely at the lowest possible cost.

A typical sand filter system has four working parts:

1. The septic tank.
2. The pump chamber with the pump.
3. The sand filter.
4. The Chlorinator

The Septic Tank

The typical septic tank is a large buried container made of concrete, fiberglass or polyethylene. Wastewater from your home flows into the tank. Heavy solids settle to the bottom where bacterial action partially decomposes them. Most of the lighter solids, such as fats and grease, rise to the top and form a scum layer.

The wastewater leaving the septic tank is a liquid called effluent. It has been partially treated but still contains disease-causing bacteria and other pollutants. From the tank, the effluent flows by gravity into the pump chamber.

Proper Care Includes:

1. Inspecting your septic tank once every year and pumping it when needed. If the tank is not pumped periodically, solids escaping from the septic tank will clog the pump, sand filter, and drainfield. Using a garbage disposal will increase the amount of solids entering the tank and require more frequent pumping.

2. Avoiding the flushing of harmful material into the septic tank. Never put grease, newspapers, paper towels, cigarettes, coffee grounds, sanitary napkins, solvents, oils, paint, and pesticides into the tank. For information on the proper disposal of hazardous household waste, call the Recycle Hotline, 1-800-RECYCLE.

3. Avoiding the use of any type of chemical or biological septic tank additive. Additives do not improve the performance of the tank. They do not reduce the need for routine pumping, and some are even harmful to the system.

The Pump Chamber

The pump chamber is a concrete, fiberglass or polyethylene container that collects the septic tank effluent. The chamber contains a pump, pump control floats, and a high-water alarm float. The control floats are adjustable and are set for pumping a specific volume of effluent. When the effluent rises to the level of the "ON" float, the pump starts delivering the effluent to the sand filter. The pump lowers the effluent level to the "OFF" float and stops.

The high-water alarm float in the pump chamber starts an alarm to warn you of any pump or system malfunction. The float is set to start when the effluent in the pump chamber rises above the "ON" float. The alarm should consist of a buzzer and an easily visible light. It should be on an electrical circuit separate from the pump.

The pump discharge pipe should have a union or other quick disconnect coupler for easy removal of the pump. A piece of nylon rope or other non-corrodible material should be attached to the pump for taking the pump in and out of the chamber.

Proper Care Includes:

1. Checking the pump chamber, pump and floats every year and replacing or repairing worn or broken parts. Pump maintenance should follow the manufacturer's recommendations. Check electrical parts and conduits for corrosion. If the alarm panel has a "push-to-test" button, it should be checked regularly.

2. Installing a septic tank effluent filter or pump screen, if your system does not have one. Screening or filtering the septic tank effluent provides an effective way of preventing solids from clogging the pump and pipes. Inspecting a screen or filter, and cleaning it, when necessary, is quick, easy, and prevents costly damage from solids entering the system.

3. Taking action to protect the sand filter and drainfield after a prolonged power outage or pump failure. Effluent will continue to collect in the pump chamber until the pump resumes operation. With additional effluent in the chamber, the pump may deliver a volume greater than the sand filter or drainfield can handle. If all of the reserve storage inside the chamber is used, the plumbing in your home can backup. When the pump is off for more than 6 hours, the following measures can be taken to help protect your system:

1. Reduce your water use to a minimum.
2. Turn off the pump at the control panel.
3. After power is restored or pump service is completed, switch the pump on and let it run for 5 minutes maximum, and turn it off again. Repeat this manual switching every 6 hours until the effluent drops to the "OFF" float level and the pump turns off automatically. If there is little water use during the outage or pump service, the pump may automatically turn off during the first manual switching.

Do not enter the pump chamber. Gases inside pump chambers are poisons and the lack of oxygen can be fatal. The service or repair of pumps and other electrical equipment must be done by an experienced person.

The Sand Filter

The typical sand filter is a concrete or PVC-lined box filled with a specific sand material. A network of small diameter pipes is placed in a gravel-filled bed on top of the sand. The septic tank effluent is pumped under low pressure through the pipes in controlled doses to insure uniform distribution. The effluent leaves the pipes, trickles downward through the gravel, and is treated as it filters through the sand. A gravel underdrain collects and moves the treated wastewater  for discharge.

The Chlorinator

The Chlorinator receives the treated effluent for treatment. The Chlorinator feeds a metered amount of calcium hypochloride, to disinfect the wastewater prior to discharge.

The Chlorinator should be filled a least once every spring or summer to insure a proper level of disinfection, the chlorinator should be filled with chlorine tablets specifically designed for wastewater applications, never use pool chlorine tablets.

Proper Care for a Sand Filter Includes:

1. Knowing where your system and replacement area are located and protecting them from damage. Before you plant a garden, construct a building, or install a pool, check on the location of your system and replacement area.

2. Practicing water conservation and balancing your water use throughout the week to keep from overloading the system. The more wastewater you produce, the more the sand filter and soil must treat and dispose. You can reduce your water use by installing water-saving devices, repairing leaky plumbing fixtures, taking shorter showers, and washing only full loads of dishes and laundry.

3. Diverting water from surfaces, such as roofs, driveways, or patios away from the system or replacement area. Soil over your system should be slightly mounded to help surface water runoff. Sprinkler systems do not belong in the area of the sand filter or drainfield.

4. Keeping traffic, such as vehicles, heavy equipment or livestock off your system and replacement area. The pressure can compact the soil or damage pipes.

5. Landscaping your system properly. Do not place impermeable materials over your system or replacement area. Materials, such as concrete or plastic reduce evaporation and the supply of oxygen to the soil needed for proper effluent treatment. Grass is the best cover for your entire system.

6. Inspecting the sand filter and drainfield areas for odors, wet spots, or surfacing sewage periodically. Check your system's inspection pipes regularly to see if there is a liquid level continually over 6 inches. This may be an early indication of a problem.

Additional Information

For more information on septic-system care, inspection and maintenance, call Gullett Sanitation Service Inc. at 513-734-2227 or Email  us at: dangullett@gullettsanitation.com with questions or comments.
Last modified: April 18, 2008