You need to talk to the water company and not listen to your builder. It’s worrying that he is unaware that you can’t have access to the drain inside the house
Is this extension being done under a building notice?Yes BC asked us to get the build-over agreement for that. I was not familiar with the rules and the builder was so confident to suggest we raised it to the floor level and left it accessible. Now I know we are not allowed...I should have spent more time to check. Does the one outside need to be removed as well?