I have a 2" trap arm for a lav, and just realized a 1-1/4" lav drain can't
use a 2" trap. The UPC shows the trap arm size must match the trap
size, but does anyone know what problem a 1-1/4" trap on a 2" trap
arm would cause? Self siphoning should actually be less than a smaller
sized arm, so I'm not sure what the problem would be if I just go ahead
and put the 1-1/4" trap on.