After months in the design stage and a good few weeks in the making, we are now the owners of possibly the only narrowboat with a decorative stench pipe.It's rather elegant in brass and metal of the type is often used as an engine chimney on historic narrowboats. So it doesn't look out of place but hides its real function.
On our boat, the combined vent and rinse point from the toilet holding tank is fitted in the roof skin. And the whiff from this pipe can be quite intense.
Now, it needs to be stated that I am no expert in fluid dynamics and most of the theories here are a bit home baked. But I think what is happening is that a boundary layer effect is allowing the venting gases to hug the outside surface of the boat and creep in through any open windows and portholes.
Now houses traditionally have soil stacks or stench pipes. The simpler ones just vent to the atmosphere. Household Building Regulations require that the top of the vent pipe must be 900mm above any window. Presumably this is to both avoid the boundary layer problem and get the gases (which are slightly lighter than air) into the atmosphere and maybe into a breeze.
Household stench pipes have been in common use for over 150 years and in all the houses I have lived in, they have worked very successfully. So, we figured there was no point in looking any further.
The stack was fitted yesterday and after a few exhaustive tests, it does appear to be a success. Now we can catch the summer breeze without any noxious top notes.