In a house I am about to renovate, there is a strange plastic pipe in
the outside toilet. My house has flat-roofed kitchen extension
including the loo, and next door has an ajoined pitched roof extension.
There is a black plastic drainpipe running the width of my outside loo,
terminating in a grille on the outside wall next to the door. The other
end of the pipe seems to go into the wall, as if it is going through to
next door, but I cannot see if it goes in or not without digging out
some brick etc. Eventually I will be able in investigate properly, but,
has anyone seen anything like this, or know what it could be ?

ASCII art follows, please view in fixed font.


___________________
| _____ |
ventilation | | | |
grille - :===========| - plastic drainpipe
| | | | above toilet bowl
| | loo | | about 4 feet from floor
my | ( ) |
patio | ~~~~~ | party wall
\ | and unknown
door \ | things nextdoor !
\ |
| |
|___________|_______


Cheers,
Simon.