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| Typical Residential On-Site Sewage Disposal System (Gravity Flow Type) |
Septic tanks may have one or two compartments. Two-Compartment Tanks do a better job of
settling solids and are required in some areas for new installations. The additional
compartment provides one more chance to catch any solids that may have escaped the initial
settling area.
Baffles at the tank's inlet pipe slow the incoming wastes and reduce disturbance of the
settled sludge. A baffle at the outlet keeps the sludge and scum from exiting the septic tank.
An effluent filter, such as those made by Zabel are a good idea for placement on the tank
outlet. They are available in a variety of styles and sizes and offer an inexpensive additional
safety net for maintaining the cleanest possible effluent. The cleaner the effluent enter the
soil absorption field, the longer the system life will be. All septic tanks should have access
covers for servicing the baffles, the effluent filter, and for pumping both compartments.
settling solids and are required in some areas for new installations. The additional
compartment provides one more chance to catch any solids that may have escaped the initial
settling area.
Baffles at the tank's inlet pipe slow the incoming wastes and reduce disturbance of the
settled sludge. A baffle at the outlet keeps the sludge and scum from exiting the septic tank.
An effluent filter, such as those made by Zabel are a good idea for placement on the tank
outlet. They are available in a variety of styles and sizes and offer an inexpensive additional
safety net for maintaining the cleanest possible effluent. The cleaner the effluent enter the
soil absorption field, the longer the system life will be. All septic tanks should have access
covers for servicing the baffles, the effluent filter, and for pumping both compartments.
The septic tank handles the initial treatment of all wastewater. Every on-site septic tank is
connected to the home's sewer line and is responsible for the settling and biological
treatment of solids within the wastewater. Raw waste water and solids from the bathroom,
kitchen and laundry room flow into the septic tank where the solids separate from the liquid.
Light solids, such as soap suds and grease, float to the top and form a scum layer. This
layer remains on top and gradually thickens until you have the tank cleaned. The liquid
waste (middle layer) goes into the soil absorption field while the heavier solids settle to the
bottom of the tank where they are gradually decomposed by bacteria. Some
non-decomposed solids remain, forming a sludge layer that eventually must be mechanically
removed from the septic tank. Many people think that the septic tank is the only component
in their septic system, and that it must be pumped out when it gets full. Normally a 1,500
gallon septic tank will fill up in about 1-1/2 to 2 weeks. This is normal and the septic tank will
remain full of water until you have it pumped out. The more important filling of the septic tank
is the accumulation of sludge. This happens gradually over time, and when the sludge builds
to about 20% of the tank capacity it is time to have it removed. For a household of 3 people
and a septic tank capacity of 1,500 gallons, a 3 year pumping / cleaning is recommended.
More detailed information about septic tank pumping can be seen by clicking here.
Massachusetts Title 5 regulations require a 1,500 gallon septic tank in most cases. In all
cases a minimum size of 1,000 gallons applies to all sub-surface disposal system vessels
(except the distribution box). The most popular type of septic tanks are made of concrete,
but plastic and fiberglass are also available. The septic tank is the only component of the
septic system that requires routine maintenance.
Below are some pictures of septic tanks.
connected to the home's sewer line and is responsible for the settling and biological
treatment of solids within the wastewater. Raw waste water and solids from the bathroom,
kitchen and laundry room flow into the septic tank where the solids separate from the liquid.
Light solids, such as soap suds and grease, float to the top and form a scum layer. This
layer remains on top and gradually thickens until you have the tank cleaned. The liquid
waste (middle layer) goes into the soil absorption field while the heavier solids settle to the
bottom of the tank where they are gradually decomposed by bacteria. Some
non-decomposed solids remain, forming a sludge layer that eventually must be mechanically
removed from the septic tank. Many people think that the septic tank is the only component
in their septic system, and that it must be pumped out when it gets full. Normally a 1,500
gallon septic tank will fill up in about 1-1/2 to 2 weeks. This is normal and the septic tank will
remain full of water until you have it pumped out. The more important filling of the septic tank
is the accumulation of sludge. This happens gradually over time, and when the sludge builds
to about 20% of the tank capacity it is time to have it removed. For a household of 3 people
and a septic tank capacity of 1,500 gallons, a 3 year pumping / cleaning is recommended.
More detailed information about septic tank pumping can be seen by clicking here.
Massachusetts Title 5 regulations require a 1,500 gallon septic tank in most cases. In all
cases a minimum size of 1,000 gallons applies to all sub-surface disposal system vessels
(except the distribution box). The most popular type of septic tanks are made of concrete,
but plastic and fiberglass are also available. The septic tank is the only component of the
septic system that requires routine maintenance.
Below are some pictures of septic tanks.
The next step in wastewater treatment occurs in the soil beneath the drainfield. The drainfield
consists of a distribution box connected to long underground perforated pipes, dry wells or
leaching chambers (such as those manufactured by Infiltrator). The network of pipes is laid in
gravel-filled trenches (2-3 feet wide), or beds (over 3 feet wide) in the soil. Liquid waste or
effluent flows out of the tank and is evenly distributed into the soil through the piping system.
The soil beneath the drain-field provides the final treatment and disposal of the septic tank
effluent. After the effluent has passed into the soil, most of it percolates downward and
outward, eventually entering the groundwater. A small percentage is taken up by plants
through their roots, or evaporates from the soil. The soil filters the effluent as it passes
through the pore spaces. Chemical and biological processes treat the effluent before it
reaches groundwater, or a restrictive layer, such as hard pan, bedrock, or clay soils. These
processes work best where the soil is somewhat dry and permeable, and contains plenty of
oxygen for several feet below the drain field. The infamous "candy cane" looking pipes
protruding upward from a newer Title 5 compliant drainfield are air vents to aid in the
introduction of oxygen onto the absorption bed. Although the vent is an eyesore, the benefits
of oxygen in the absorption field are significant and will help maximize the life of the drainfield.
The size and type of drainfield design depends on the seasonal high ground water level,
estimated daily wastewater flow, soil conditions, and soil type.
Below are photos of a couple types of drainfields.
consists of a distribution box connected to long underground perforated pipes, dry wells or
leaching chambers (such as those manufactured by Infiltrator). The network of pipes is laid in
gravel-filled trenches (2-3 feet wide), or beds (over 3 feet wide) in the soil. Liquid waste or
effluent flows out of the tank and is evenly distributed into the soil through the piping system.
The soil beneath the drain-field provides the final treatment and disposal of the septic tank
effluent. After the effluent has passed into the soil, most of it percolates downward and
outward, eventually entering the groundwater. A small percentage is taken up by plants
through their roots, or evaporates from the soil. The soil filters the effluent as it passes
through the pore spaces. Chemical and biological processes treat the effluent before it
reaches groundwater, or a restrictive layer, such as hard pan, bedrock, or clay soils. These
processes work best where the soil is somewhat dry and permeable, and contains plenty of
oxygen for several feet below the drain field. The infamous "candy cane" looking pipes
protruding upward from a newer Title 5 compliant drainfield are air vents to aid in the
introduction of oxygen onto the absorption bed. Although the vent is an eyesore, the benefits
of oxygen in the absorption field are significant and will help maximize the life of the drainfield.
The size and type of drainfield design depends on the seasonal high ground water level,
estimated daily wastewater flow, soil conditions, and soil type.
Below are photos of a couple types of drainfields.
Households not served by public sewers depend on an on-site Septic System to dispose of
wastewater. There are many different types of septic systems designed to fit a wide range of
soil and site conditions. This information is on the operation of a conventional gravity-flow
septic system.
A conventional septic system consists of two main parts: the Septic Tank and the Soil
Absorption Field. (also referred to as a leach field or absorption bed). At the head of the
drainfield a Distribution Box distributes effluent to several absorption trenches or leaching
chambers. Massachusetts Title 5 requires that newly installed drainfields include a
designated reserve area should the existing septic system need an addition, repair or
replacement.
wastewater. There are many different types of septic systems designed to fit a wide range of
soil and site conditions. This information is on the operation of a conventional gravity-flow
septic system.
A conventional septic system consists of two main parts: the Septic Tank and the Soil
Absorption Field. (also referred to as a leach field or absorption bed). At the head of the
drainfield a Distribution Box distributes effluent to several absorption trenches or leaching
chambers. Massachusetts Title 5 requires that newly installed drainfields include a
designated reserve area should the existing septic system need an addition, repair or
replacement.
| Typical Residential Gravity Type Septic System |
| Cross Sectional View of a Septic Tank |
| Septic Tank shown after partial back-fill |
| Soil Absorption Bed Using Pipe and Stone Design |
| Soil Absorption Bed Using Leaching Chambers |
| Soil Absorption Bed Using Leaching Chambers |
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