EF-4 Residential Series Effluent Filter (Combo) - Walmart.com
Septic tank filter - FTB - Orenco Systems
The Septic Doctor - Myth No.6: effluent filters are not necessary. Why should I spend the money when my parents never had one on their tank and it still works fine.
Septic Tank Effluent Filter | Sim/Tech STF-110 Gravity Flow