I have a problem with sewers/drainage, what do I do?

This is not a matter that is covered by the planning legislation.

Generally speaking, you're usually responsible for drains inside the boundaries of your property, while the sewerage company is responsible for lateral drains, which are outside of property boundaries, and sewers. Although most sewers are now publicly owned, there are still some private or unadopted sewers.

If your property is served by one of these, you may be responsible for maintaining it.