Putting a Zabel filter on your exit pipe and using septic scrub once a year will make your drain field last many, many years (maybe your life time). I've noticed that using a baffel/tee on your exit pipe, you can still get toilet paper, grease and some solids into your drain field. Every one do yourself a favor. Use Septic scrub once a year and add a Zabel filter to your exit pipe. This is from my own experience. My drain field was in poor shape three years ago..... Now it works like a new one or close to it!