Mound Septic System

Septic tanks with gravity flow drainfields 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 Mound System is one alternative, which provides:
  • Dosing and resting cycles.
  • Uniform distribution of effluent.
  • Known level of sewage treatment in the sand fill before disposal.
  • Greater distance for effluent to travel before reaching groundwater.
Mound Septic System Installation - Stangland septic service in Aberdeen, WA
Typical Mound System has three working parts:
  1. The septic tank.
  2. The pump chamber with the pump.
  3. The mound with its replacement area.
Mound Septic System Components - Mound Septic System Installation - Stangland septic service in Aberdeen, WA

The Septic Tank

Spetic Tank Installation - Mound Septic System Installation - Stangland septic service in Aberdeen, WA
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 grease and oils, 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 to the pump chamber.

The Pump Chamber

Pump Chamber - Mound Septic System Installation - Stangland septic service in Aberdeen, WA
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 pump action may be controlled either by the use of control floats or by timer controls. Control floats are set to turn the pump “ON” and “OFF” at levels for pumping a specific volume of effluent per dose. Timer controls are set to produce both the length of the dose and the interval or rest period doses.

The high water alarm float sounds an alarm to warn you of any pump or system malfunction. If pump timer controls are used, the alarm also will warn you of excessive water use in the home. 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 and valve for easy removal of the pump. A piece of nylon rope or other noncorrosive material should be attached to the pump for taking the pump in and out of the chamber.

The Mound

Mound Drain-Field - Mound Septic System Installation - Stangland septic service in Aberdeen, WA
The mound is a drainfield that is raised above the natural soil surface in a specific sand fill material. Within the sand fill is a gravel filled bed with a network of small diameter pipes. Septic tank effluent is pumped through the pipes in controlled doses to insure uniform distribution throughout the bed. The effluent leaves the pipes under low pressure through small diameter holes, and trickles downward through the gravel and into the sand. Treatment of the effluent occurs as it moves through the sand and into the natural soil. Every new mound is required to have a designated replacement area. The replacement area should be protected in case the existing system requires an addition or repair.

Proper Care Includes:

  1. Knowing where your system and replacement area are located and protecting them. 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 mound must treat and dispose of.
  3. Diverting water from surfaces such as roofs, driveways, or patios away from the mound and replacement area. The entire mound is graded to provide for runoff. Place structures, ditches, and driveways far enough away so that water movement from the mound is not disrupted.
  4. Keeping traffic, such as vehicles, heavy equipment, or livestock off your mound and replacement area. The pressure can compact the soil or damage pipes.
  5. Landscaping your mound properly. Do not place impermeable materials over your mound or replacement area. Materials, such as concrete or plastic reduce evaporation and the supply of air to the soil needed for proper effluent treatment. Grass is the best cover for the mound.
  6. Inspecting the mound and downslope 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.

What if your alarm sounds?

If for any reason the effluent level inside the pump chamber reaches the alarm float (faulty pump, floats, circuit, excessive water use, or another problem), the alarm light and buzzer will start. By using water conservatively (avoid baths, showers, and clothes washing), the reserve storage in the pump chamber should allow you enough time to get the problem corrected. To silence the alarm, push the reset light on the alarm panel. Before calling for service or repair, check to see if the problem could be:

  1. A tripped circuit breaker or blown fuse. The pump should have a separate circuit with its own breaker or fuse. If it's on a circuit with other equipment, that equipment can cause the breaker to trip.
  2. A pump or float switch power cord plug that has come unplugged. If electrical connections are the plug-in type, be sure switch and pump plugs are making good contact in their outlet.
  3. Control floats tangled by other parts in the chamber such as the electric power cord, lifting rope, or pump screen. Be sure floats operate freely in the chamber.
  4. Debris on floats and support cable that is causing the pump to switch off. Lift the floats out of the chamber and clean.

CAUTION: Always turn off the power supply at the circuit breaker and unplug all power cords before handling the pump or floats. Do not enter the pump chamber. Gases inside pump chambers are poisonous and the lack of air can be fatal. If the problem cannot be located with the above steps, call your pump service person or on-site system contractor for service or repair. The service or repair of pumps and other electrical equipment must be done by an experienced person.