Like all legislation it then leaves plenty of room for lawyers to earn their crust as it give a definition of prejudicial to health, but not of nuisance
Whether water vapour is prejudicial to health is debatable and a plume of water vapour may be unsightly but is it a "nuisance"?
Bring on Rumpole
I thought you were Rumpole!
I think that its well established that boiler products of combustion are prejuducial to health as they contain carbon monoxide.
Although probably not tested in court, there must now be many cases where EHOs have taken the view that flue pluming close to windows is a statutory nuisance.
However, "guidance" (not compulsory) in the Government document "Guide to the Condensing Boiler Installation Assessment Procedure for Dwellings" extends the "J"'s 600mm to "a minimum 2·5m from a facing wall, fence, building, or the property boundary" for condensing boilers.
Again, this applies only to a flue pointing in that direction. British Standard BS5440-1 also "recommends" that condensing boiler flues should not be sited where the plume is "likely to cause a nuisance".
Tony