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The French are considered the first to use an underground septic tank system in the 1860’s. By 1880, two-chamber septic systems were being used in the United States. Today, nearly one in four households in the United States depends on an individual septic (onsite) wastewater treatment system or small community cluster system to treat waste water. When used properly, an onsite system can function very well for many years. If used improperly, the system will fail and cause conditions that threat human health and the environment. Inspection and maintenance is key to ensuring that septic systems function properly.
The term “septic” refers to the anaerobic bacterial environment that develops in the tank and which decomposes or mineralizes the waste discharged into the tank. Septic tanks can be coupled with other on-site wastewater treatment units such as biofilters or aerobic systems involving artificial forced aeration.
A septic tank generally consists of a tank (or sometimes more than one tank) of between 4000 and 7500 litres (1,000 and 2,000 gallons) in size connected to an inlet wastewater pipe at one end and a septic drain field at the other. These pipe connections are generally made via a T pipe which allows liquid entry and exit without disturbing any crust on the surface. Today, the design of the tank usually incorporates two chambers (each of which is equipped with a manhole cover) which are separated by means of a dividing wall which has openings located about midway between the floor and roof of the tank.
A typical house will have all wastewater discharge through a single pipe, called the building sewer pipe, which delivers the wastewater by gravity to the sewage disposal system, typically the tank. The sewer lines that carry solids form the house to the tank should have sufficient slope to maintain velocities that carry solids. A slope of between 1 percent (1/8 inch per foot) and 2 percent (1/4 inch per foot) is generally recommended. The last 15 feet of sewer line before the tank should not slope more than 2 percent (1/4 inch per foot). The sewer line from the house to the tank, all fittings and the pipe in the tank, all extensions to the surface from the top of the tank and the first 10 feet exiting the tank must be schedule 40 PVC pipe or heavier.
As solids enter the tank, the clear zone is reduced. If there’s not enough of the clear zone, then the wastewater entering the tank will push the stuff out of the tank before it gets enough time to separate. Wastewater with unsettled solids will be pushed out of the tank and can clog a soil absorption system.
To prevent this from happening, tanks need to be pumped to maintain a good “clear zone.” Failure to pump regularly will cause the absorption field to fail. Routine pumping of the treatment tank is the best way to prevent system failure.
In most areas, a newly installed septic tank is required to be a minimum of 1,000 gallons in size. The minimum septic tank capacity is based upon the number of household bedrooms. For 3 bedrooms, the minimum size is 1,000 gallons. For 5 bedrooms, the minimum size is 1,500 gallons.
Treatment tanks should not be entered during a typical septic inspection. Treatment tanks are hazardous environments. Work carefully and safely. Sewage contains germs that can cause diseases. Never enter a septic tank. Toxic and explosive gases in the tank present a hazard. Do not bend over or stick your head towards an open tank. The gases that come out of the tank may cause you to lose consciousness. You may lose your balance and could end up falling into the tank. Do not reach with your hand into the tank. Old tanks may collapse. Secure the septic tank lid so that children cannot open it. Do not enter cesspools. Do not work alone. Do not bring sewage-contaminated clothing into the home.
Methane and hydrogen sulfide gases are produced in a septic tank. They are both toxic and explosive. Hydrogen sulfide gas is deceptive. It can have a very strong odor one moment, but after exposure, the odor may not be noticed.
The absorption area is the most critical component of the onsite treatment system. Breakout of septic effluent to the ground surface is a system failure. The system in this condition has failed and is not functional. If you observe or have reason to believe that the system is discharging directly to the surface of the ground, or to the surface or ground waters, such conditions should be noted in your report. The inspector does not have to continue the inspection as the system’s condition can be described as “failed” and “non-functional.”
The Barrie Home Inspector recommends that you have a licensed septic system installer inspect and pump your system prior to taking possession of your new home. The installer will inspect the inlet and outlet baffles after pumping the tank. The inlet and outlet baffles are somewhat susceptible to damage and should be treated with caution. They will break if they are hit with an instrument like a shovel. Do not tap or pick at the baffles. If the baffle appears to have damage such as a crack or a missing piece then report the condition. The baffles are designed to protect the absorption area from solids entering it. The baffle holds the solid materials in the tank and blocks them from entering the pipe that runs towards the field. If a baffle is missing or deteriorated, the baffle should be repaired or replaced by a professional contractor. The inspector should then discuss with the client about the potential problems associated with a broken baffle allowing solids to enter the absorption area.