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On average, septic tanks should be pumped every 3 to 5 years, depending on the size of the tank, the number of family members contributing waste to the system, and the kinds of solids that go down the drain. Most solids that enter the system are decomposed by the bacteria in the tank. Eventually, non-organic junk, such as sand and bits of plastic, accumulate on the bottom of the tank, while a layer of floating grease and scum accumulates on top. These solids reduce the efficiency of the system and make pumping necessary.
Larger septic tanks need pumping less frequently than smaller ones because they have a larger capacity for junk and scum. Likewise, the fewer people who use a system, the less often pumping will be needed. For example, a 1,500-gallon system being used by a family of four might need pumping every five years, while a smaller tank would require pumping twice as often. After the kids have grown and flown, a 1,500-gallon used by empty-nest parents might only need pumping every 10 years.
Garbage disposals can also affect the frequency of septic pumping because they increase the volume of solids in the system. And undigested solids, such as those from a garbage disposal, take longer to decompose.
Additives to septic systems are widely recommended, but their benefits are doubtful. Controlled studies have not shown them to improve the performance of septic systems in any significant way. Added enzymes and bacteria cannot break down non-organic sediment. And added bacteria must compete with the bacteria already in the tank. In most cases, the established bacteria simply eat the added ones.
Home inspections do not include an exaustive evaluation of a septic system. We recommend that you have the seller of the property provide you with documentation from the service company detailing the service that they have provided and ask for their opinion on the need for further investigation. If this information is not available an examination of the system is recommended. Our inspection will include a visual inspection of the the area of the property that we believe the leaching bed is present, this may reveal some failures but is not a subtistute for thorough professional evaluation.
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