This is not HVAC related, but the guys on this board seem to have the best info on most topics, so I figured you could help me out. I am having recurrent clogging problems with my house's drains. Probably roots getting into the main in the yard. Anyway, this house does not have a main sewer line clean out outside the house. The roto-rooter guy has (twice in a week) snaked the drain 75' accessing the main from a removed toilet. Long story short: because there are back to back toilets, he cannot get the snake into the line with the blade on the end, so he did not really solve the problem, just got the water to go down. Now when we use the laundry, the water backs up filling the bathtub, and will slowly drain. He recommended installing a clean out in the main 3" line outside so he could get the blade in. I dug a hole to expose the line about 2 1/2' down and found the cast iron pipe where it leaves the house. What is the best procedure to install a cleanout here? Thanks. Keith