Among the possible vacuum-breaking systems named in the Virginia Graeme Baker Pool and Spa Safety Act is a suction-limiting vent.
(The other two options — gravity drainage systems and drain
disablement — are meant to prevent a vacuum from forming
altogether and are not discussed here.)
Suction-limiting vents are produced on site by a plumber at the
time the pool or spa is constructed. The process involves branching
an independent pipe off the drain line and exposing it to
This vent is filled with water. If a vacuum forms in the suction
line, water is pulled from the vent pipe, thereby eliminating the
Because suction-limiting vents require only plumbing, these systems
can be inexpensive.
However, some say each one should be engineered to the specific
pool to account for issues such as the length of pipe and vacuum
inherently built into the system. This can guarantee that the vent
line performs quickly, but it also can offset the cost savings
gained over using an SVRS or automatic pump shut-off.
With no moving parts, some like the vent’s chances of
functioning without incident over long periods of time. But there
are other professionals who have concerns about these
They cite the fact that, rather than being produced in a controlled
manufacturing facility, suction-limiting vents rely solely on the
expertise of the on-site installer and his or her willingness to
have the plumbing properly engineered.
Secondly, the pipe is not part of the closed circulation system, so
the water inside doesn’t move and can become stagnant.
In addition, the pipe is open to atmosphere, allowing in dirt and
bacteria, and leaving some to worry that the vent could prove a
breeding ground for waterborne illnesses.
However, this concern has been debunked, says Steve Barnes,
chairman of APSP’s Technical Committee, who likens the vent
to a spa air-intake pipe that operates under the same