For hydro-jetting, isolate the line, install a backflow preventer, start with lower PSI, then increase as needed

https://mighty-wiki.win/index.php/The_House_owner%27s_Guide_to_Budget_Sewage-disposal_Tank_Emptying_and_Maintenance

For hydro-jetting, separate the line, install a backflow preventer, begin with lower PSI, then increase as required, using appropriate nozzles to search biofilm, roots, and scale without damaging pipes.