We wanted the 3 inch PVC pipe for
the new greywater
wetland system to have a
slight downhill slope.
There's no glue holding the
pieces together to take advantage of a little wiggle room that allows
the pipe to point a shade downward instead of straight ahead.
A brick underneath holds it
in place without any leaks.
If there is suffucient play between the T and the pipe for it to angle down when dry, it would do the same when glued.
Besides, the construction wouldn't be stiff enough when glued to hold the pipe exactly horizontal without supports.