Generally when a lateral is added to a cesspool, it is because the cesspool is not draining properly. Based on your comments, I would suggest that you treat the cesspool first and not worry about the lateral yet. Have the cesspool pumped and then have the pumper back-flush the bottom to break up the crust. Then add two bottles of Septic-Scrub the first day and two more the second. You will probably need to add some more in the near future. I usually suggest that you have a riser put on the lid of the cesspool of at least six inch pipe and the hang a fishing float so that it hangs at about the 30-40 % full level. When it floats, than another two bottles of Septic-Scrub should be added. The cesspool probably should be pumped at least every two years, depending on how many are in your family. If you do this, you will probably never use the lateral again. If you want to use the lateral system, then I would suggest cutting into the pipe and putting T connection and riser on the pipe leading to the lateral. This would allow you to treat the lateral without going through the cesspool. If you would like to further discuss your situation, please call me.