We live in a house which was built in the 1960s and the sewage pipe on our side joins in with the neighbours pipe and then out to the public sewage system. Over the last couple of days our next door neighbour has threatened to close off access to his sewage pipe, effectively leaving us in a situation where the sewage will back up into our house. We believe this is a EPA health hazard and is essentially illegal. Can someone advise please on what we should do if he does actually block this up over the coming days?