Sec. 491(14). Replacement of old fixtures.
When new fixtures are introduced on old work, it will not be
compulsory on the part of the owner to back vent same, but they
shall have non-syphoning traps of approved type and in changing
closets, only syphon closets with tanks will be allowed.
Where there are no closets above, it will not be necessary to
back vent fixtures, but the soil or waste pipe must be in every
case extended (not less than two inches in size) the required
distance above the roof, or into other vent pipe above highest
fixture. On repair of old work, in lieu of back vent pipe, a
non-syphoning trap of approved type when connected with a
wash basin, sink, urinal or wash tray, which is not more than
fifteen feet from a main, will be permitted.
