We are looking to add a light over our kitchen sink, but in the ceiling space just above is also the waste pipe for the toilet, and a cold water supply for filling it.

While knock on wood we have been fortunate to not have any issues with the piping or toilet overflow, of course it can indeed happen.

So in order to be able to add an over sink light, is there any special precaution, special box, etc. that should be used?

The good news is that we are putting up a tin ceiling, so will have plywood instead of drywall up there (currently there is no ceiling, so I can see the joists and everything up there). So, for all it matters to me, I could make junctions far away, and run water-tight conduit to an outdoor type (IP 6 I think) box facing down, and have that be the setup, totally sealed and wart tight.

Or I could do something else based upon your experience with this stuff and the associated best practices.

Any advice would be great.

Thanks!