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Conducting the Sanitary Survey

Written records may be out of date or contain inac- curacies, and new developments may not be recorded on municipal tax maps. Interviews with property owners are a useful way of gathering information such as known problems, age of system, system location, usage, and

the last time the septic tank was serviced. Maintain a courteous and professional demeanor while interviewing property owners in person or on the telephone. Sanitary surveys are a good opportunity to educate owners about how to properly maintain their system.58

It is illegal and a violation of the Maine Subsurface Wastewa- ter Disposal Rules to operate a “malfunctioning” subsurface wastewater disposal system. A malfunctioning system is one that is neither treating wastewater, nor functioning properly.55 Reasons for a malfunction can include:

The system may be improperly sited, constructed, or designed (e.g., systems built in a high water table, located in poorly suited soils, improper fill).

Tree and/or shrub roots break pipes and interfere with the distribution system.

Heavy machinery or cars may crush pipes and/or crack the septic tank.

The system may be compro- mised by disposal of hazardous chemicals, oil, and other sub- stances which interfere with biological digestion.

Heavy water use and flush- ing of non-toilet paper items (diapers, paper towels, tam- pons, etc.) exceed the system capacity.

The tank is not pumped out regularly. The “clear” zone of the tank is not maintained and the system is clogged by sludge and scum.

to 1,500 gallons, depending on the

number of bedrooms served. Old- er tanks may be round and made of substandard material such as metal, where rusting can compro- mise the structural integrity. Tanks hold wastewater while the solids (sludge) sink to the bottom to de- compose. Grease, oil, and other lightweight material (scum) float to the surface and become trapped in devices (usually baffles or sanitary tees) at the tank’s inlet and outlet. Effluent leaving the tank enters the soil absorption system.

Raw wastewater is treated in septic tanks through anaerobic decomposition, a process where microorganisms in the tank digest much of the organic matter. Some newer septic systems aerate the raw wastewater and utilize aerobic decomposition, which generally produces a cleaner effluent and may allow the size of the leach field to be decreased.This can be impor- tant in locations where the area for a leach field is limited.57

The area (clear zone) within the septic tank between the scum and sludge zones has relatively “clean” seepage, which passes out of the tank to the soil absorption system.

It is typical for solids to build up in the tank before they decompose, reducing the clear zone in the tank. When this area becomes too nar- row, unsettled solids will bypass the effluent tee or baffles and clog the soil absorption system and eventually result in a wastewa- ter breakout and/or a plumbing back-up. A significant amount of excess water may be added to the septic system by outdated or faulty plumbing. Home plumbing inspections should include care- fully checking all plumbing, water fixtures, and water-using devices for malfunctions.55

Tanks must be pumped regularly to maintain the clear zone and the integrity of the soil absorption sys- tem. The frequency of pumping depends on the water usage, the size of the tank, and the volume and type of waste. On average, a three- to five-year pump-out schedule for a year-round single- family home is sufficient. One way to assess whether or not the tank still has working capacity is to re- move the cover, shovel a hole in the floating sludge and measure its thickness, then use a “Sludge Judge” to assess the thickness of the sludge on the bottom.57


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