Not sure whether to be concerned about this. We are looking to buy a new build place that due to the other properties around it has a sewer diversion in place, part of which runs beneath the garage and some running under the garden. As it's new build it has 10 year NHBC so all the works must have been signed off as ok. Just wondered whether anyone had any experience of this? We would need to allow access to two neighbours if there were any blockage issues as the access points are in our front/back garden. I'm guessing tons of houses have sewers below them or through their garden so probably nothing to worry about. (Thinking about it, our current house has sewer running under our patio!). If you have experience/reassurance please let me know. Thank you.