The Infiltrator IM-1250 is a lightweight strong and durable septic tank. This watertight tank design is offered with Infiltrator’s line of custom-fit risers and heavy-duty lids. Infiltrator injection molded tanks provide a revolutionary improvement in plastic septic tank design, offering long-term exceptional strength and watertightness. Do not install the tank in vehicular traffic areas. The tank is designed for non-traffic applications.