We have a root growing into a toilet between the flange and foundation. The root bundle removed (for the third time) was over 2" in diameter. The closest plants are 20 feet away--red tips, crepe Mertles, and live oaks. Can you identify the tree/bush from the root either by the distance, a photo of the root, or a sample of the root? Should I mail the root to you for analysis?
Travis County Texas trees and shrubs
Oh no! That's a terrible situation. Unfortunately, it is not possible to identify a plant by its roots.
As to the situation with your pipes: roots do not invade pipes unless there is a leak. Either the pipe leaked first, or large roots broke the pipe as they were growing and caused a leak, which they then took advantage of. When roots get very large, they may break a pipe, simply in the act of growing around it and putting pressure on any places where one pipe is joined to another.
I know that you've fixed the situation in the past, and it still recurs, so I'm sorry not to have better news for you. You could start by removing the closest plant to the area. The culprit could indeed be any of the plants that you named. The only way to be completely sure that you could control the problem would be to remove all of the plants. 20 feet of root space is definitely not enough for a mature live oak, so trying to keep it out of the area of your pipes would not work. Red tip Photinias and crape myrtles also get quite large, but Photinias larger than crape myrtles, so unfortunately, they may need to go as well.