re: OT Property experts-Sewage line runs across neighbors property

Not only are you responsible, you should get a servitude for the line on their property. If I were you I'd pay for the cost to repair it and talk to them about the situation and a possible easement agreement.

If they're not interested in granting you an easement you may have to abandon the line once it crosses into their property and install a new one to the main line directly through your property to the right of way.

ETA: You should definitely find a survey of your property if you have it, you should also find the subdivision plat. While it technically may be their property, their could've been a utility servitude shown on the original drawings. Then it'd be their problem to fix