Septic Tank Filter
A septic tank filter strains out solids that can leave the septic tank effluent outlet and go into the drain field (also called leach field). These solids can cause clogging in the leach field bed and eventually septic system failure.
A properly maintained filter and regular tank pump outs can prevent your drain field from being damaged and your system from backing up sewage into your home. Its a lot cheaper to prevent this kind of damage from occurring than it is to repair it after it happens. The filter needs to be checked and cleaned out periodically.
Its normal to have floating scum on the surface of the tank, but smaller solids that flow out the effluent pipe into the drain field is what the filter is intended to prevent. The cleaner the water going out to the leach field the longer it will function trouble free.
Location Of Filter...
The filter can be located inside the tank at the outlet tee or it can be installed outside the tank on the drain field side.
Primary Cause Of Septic System Failure...
Probably the main cause of septic systems failure is clogging of the drain field as a result of lint from washing machines. Yes, lint from your clothes goes down the drain and into the septic tank. If the tank does not have a filter installed then the lint makes it way into the drain field and clogs it over time. It doesn't break down easily and floats to the surface of the tank and then out the effluent side to the leach field.
Another Solution...
A simple way to keep the lint out of a tank is to install a filter at the washing machine drain hose. Its easy to open and clean and its very accessible. A great way to protect your system if you don't have a septic tank filter installed. One of the leading brands of these filters is the Filtrol 160.