1) It's better to use licensed plumber to do sewer line work to avoid problems.
2) To save the cost, you may consider to hire a couple 勞模 to do digging work. If you do the digging part, the plumber's bill can be significantly reduced.
3) Permit is optional in the most cases. However you can double check with the plumber. If they say it's ok to get around without a permit, you will be totally fine.
4) Be environmental sensitive:
As mentioned by jy101 above, you don't want to get trouble with EPA. Sewer leak causes enviromental issues. Don't compromise with a temporary solution mentioned above.
5) Use plastic based materials such as PVC to prevent root damage again. Leave this to the plumber. They should know what they are doing.
6) Talk to the neighbor to make them aware of this situation with the following considerations:
- If they are willing to do something about the bushes, it will be the best.
- Otherwise you have the right to cut the roots within your boundary.
Good luck.
