"Speedy Jim" wrote in message
Just to clarify for OP:

The 15" side clearance is a Building Code requirement
for clear space and has nothing to do with the 12"
rough-in spec for the toilet.
http://www.onthehouse.com/wp/19980202

Jim

Exactly. Typical toilet tank is about 20" wide, but you need some clearance
on the sides for your ass to hang over and to be able to reach around with
the TT. When we put in a new washing machine in the downstairs bathroom,
it was wider than the old one and brings the clearance down to 29". I'd not
want to get any narrower than that.