There are three layers of waste in the septic system. The top layer typically floats and is considered the scum layer until to digest and falls to the bottom. The bottom layer is called the sludge layer. There is the liquid layer that lays in between the cum and the sludge layers. This is also referred to as the effluent layer. If not properly maintained, this is also the layer that is most likely to give you the sewer smell or seep through the top of the leach field if the field is clogged and not functioning properly.
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