Question:
In my 10 years of experience, the scum layer in the septic tank is thickest at the inlet end and tapers off, perhaps by 50 percent, at the outlet end. Also, the inlet pipe extends about one-third of the way vertically into the tank, whereas the outlet pipe extends halfway into the tank. This means an excessive scum layer (greater than 12 inches) usually reduces sewage flow into the tank — if not totally capping it off — long before the outlet pipe caps off.
I always measure the scum layer from the inlet end and note this for the customer.
