A guide for homeowners describing septic system types and important information to ensure trouble-free operation.

1. Homeowners Guide to
On-Lot Sewage Systems
Jeremiah Eldredge
Septic Management Services
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2. What is an on-lot sewage system?
• On-lot sewage systems are composed of two
primary parts:
• Septic tanks or an aerobic tank
• Remove the settleable and floatable solids from the wastewater
• An absorption area
• Utilizes the ability of the soil to filter and treat the remaining
effluent before it reaches the water table
• Proper maintenance of the septic tanks or aerobic
tank will prevent more costly problems with the
absorption area
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3. Sources of household sewage
Household sewage is a combination of wastewater
from toilets, showers, tubs, sinks, washing machines,
dishwashers, water softeners and garbage disposals
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4. Types of on-lot sewage systems
The basic types of on-lot systems in eastern PA are:
• Cesspool
• Septic tanks with seepage pit
• Septic tanks or aerobic tank with seepage bed
• Septic tanks or aerobic tank tank with standard trenches
• Septic tanks or aerobic tank with elevated sand mound
• Other technologies not listed here are used in special
circumstances
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5. Cesspools and Septic Tanks with
Seepage Pits
• Cesspools and septic tanks with seepage pits are no
longer permitted for installation
• Many older homes with systems installed prior to
1970 may have these systems in use
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6. Cesspools
• Cesspools are constructed of open-jointed walls
(concrete block or stone) and open bottoms
• The solids in the wastewater settle to the bottom,
while the effluent seeps through the jointed walls
and bottom
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7. Septic Tanks with Seepage Pits
• The septic tank provides for the separation of solids
from the liquid while storing the accumulated solids
• The seepage pit allows the effluent from the septic
tank to infiltrate into the soil
• The seepage pit is constructed similarly to a
cesspool
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8. Septic Tank - Soil Absorption
Systems
• The septic tank is a watertight chamber constructed
of concrete
• One of the most important components of the
septic tank is the baffle
• The inlet baffle forces the wastewater from the
building sewer line down into the tank
• The outlet baffle prevents the scum layer from
moving into the soil absorption area
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9. Septic Tank-Soil Absorption Systems
• Septic tanks have an inspection port for checking
the condition of the inlet baffle
• Septic tanks also have a manhole access port for
cleaning the tank
• Older homes may need access risers placed on the
tanks to bring the manhole opening closer to grade
to allow for proper maintenance
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10. Typical Septic System
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11. In-Ground Soil Absorption Areas
• The soil absorption area receives the liquid effluent from the
septic tanks and distributes it over a specific area
• The effluent then filters through the soil under the pipes and is
treated chemically and bacterially by the components of the
soil
• The size of the soil absorption area is based on the size of the
house and the percolation rate of the soil
• State law requires that there be at least four feet of usable soil
for the effluent to percolate through before it reaches the
water table
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12. Types of Conventional Soil Absorption
Areas
• The soil absorption area may be:
• An inground seepage bed
• A set of trenches
• An elevated sand mound
The type of system installed will depend on the slope
of the property, the depth of usable soil, and the
percolation rate
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13. In-Ground Seepage Bed
• For seepage beds, the entire absorption area is excavated
and lined with crushed stone
• The pipes (laterals) are then placed over the stone and the
entire bed area serves as an absorption area for the effluent
• Leaching chambers may be used in place of gravel
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14. Inground Trenches
• A standard trench absorption area consists of two or more
excavated trenches in which perforated pipes or laterals
distribute effluent into a layer of crushed stone under the
pipes
• The effluent is then absorbed into the soil where it is
renovated
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15. Gravity Distribution of Effluent
• Equal distribution of the effluent is very important to the
proper functioning of the system
• Most trenches and in-ground bed systems utilize gravity
distribution to the absorption from the septic tanks
• In all trench systems a distribution box is used to split the
flow equally to the individual laterals in the absorption area.
It is important that this box remain level.
• In most bed systems, a piping loop is used instead of a
distribution box
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16. Pressure Dosed Systems
• Some systems may require pressure distribution due to the
permeability characteristics of the soil
• In this type of system, the effluent from the septic tanks
flows by gravity into a dosing tank
• The dosing tank forces effluent through the distribution lines
in a controlled dose so that all pipes discharge effluent at
the same rate throughout the absorption area
• The pressure distribution system has two distinct
advantages
• The entire length of the lateral is utilized
• The soil absorption area is allowed to rest between doses
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17. Elevated Sand Mounds
• The elevated sand mound system is used in areas with reduced
permeability, shallow soils, and poor drainage characteristics
• Soils in these areas require the addition of sand above the ground to
provide for adequate renovation of the sewage prior to reaching the
water table
• The absorption area is constructed similarly to a standard seepage bed
or trench, except that the system is required to use pressure distribution
and a layer of sand must be placed between the crushed stone and the
natural soil cover
• A soil berm is placed around the mound to protect it and to provide a
suitable base for the establishment of a vegetative cover
• The mound is preceded by a dosing tank which must be equipped with
an audible and visual alarm system to alert the homeowner when a
pump failure occurs
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18. Elevated Sand Mound
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19. Aerobic Treatment Tanks
• An alternative to the septic tank is an aerobic treatment
tank
• These systems utilize an air compressor or a churning
propeller to maintain an aerobic environment for the
growth of aerobic microorganisms
• These microorganisms break down the sewage like the
anaerobic bacteria found in the septic tank
• Proper functioning of this type of treatment tank is highly
dependent upon the diligent maintenance of the mechanical
components of the aerobic system
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20. Have Questions?
Need Help?
Let us know how we can help you!
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