[220294] layer of water-in-pipe should be bottom

There are many issues with layering. Dupes change their layers (in showers?) and then sit behind tables, compactor indicators decide to go hide behind their compactors, gas bridges draw on top of buildings in front of them, pipes are drawn behind geysers, etc etc. I guess it will need some large cleanup pass one day because that's not comething that can be solved by small ad hoc changes.