dg wrote:
Do you mean the flue, condensate drain or the pressure relief pipe?

Either way IIRC, it only has to be on your side of the boundary.

But if the flue gas causes a nuisance to next door then it could be
classed as a trespass, or Statutory Nuisance. Condensate should go into
a proper drain, and relief pipe turned back to spray any hot water back
against the wall.

dg

I'm in this situation presently - the neighbours' fan-assisted flue
blows smelly exhaust into my backyard, entering the kitchen, dining
room and/or bedroom depending on which doors/windows are open and on
the prevailing wind. Boiler was fitted by plumbers employed by the
previous owner a year or so back, and the new owners aren't rich so I
wouldn't like to land them with a large bill. Is there a 'nice' way to
deal with this, other than slapping up a section of fence to break the
flow? I think the flue may contravene some of the regs stated at
http://www.makewrite.demon.co.uk/GasFitting.html but not certain
without a more careful look.

Any suggestions?

Jon.