I have found that the S-bend under our bath has a crack in it. This means that any water in the pipe leaks out (not a major issue), but this in turn means that air from the sewer can travel back up the pipe and into the house (a major issue – it stinks).
In terms of fixing the problem the piping material is metal – is it worth trying to seal the crack or is it best to get the S-bend replaced (it appears to be welded to the pipes and so this would involve getting a plumber out to replace it). Are there any sealants that would be suitable for this job (i.e. constantly holding the water in the bend in place)?