There
are few real mysteries remaining about the mechanisms at play in building
drainage and vent systems. At the center of the drainage system’s integrity is the water trap seal, which
stops sewer gas from entering a habitable space from the sewer. It comes as a surprise to many that the flow of air is as important, if not
more important, to the safe operation of the drainage system as the flow of
water. The
unsteady nature of the water flows causes pressure pressure transients, which can compromise water trap seals and provide a path
for sewer gases to enter the habitable space.