Weekly chemical adjustments of salt-chlorinated pools are not sufficient to keep the water balanced, according to new research by the National Pool Industry Research Center.
This conclusion is the result of a five-month study commissioned by
the Independent Pool and Spa Service Association.
“With a once-a-week service visit, we found that the water
chemistry of a salt-chlorinated pool will not stay within the
parameters that IPSSA considers acceptable,” said Lance Sada,
IPSSA’s liaison to the NPIRC.
Scientists at the research center monitored salt-chlorinated pools
on a weekly basis, making all chemical adjustments manually —
the pools used no automated chemical feeding, and no ORP
With weekly manual adjustments to the chlorine output, the
pools’ free chlorine concentration remained acceptably stable
throughout the study. The water’s pH, however, proved to be
more difficult to control. Every time the pH was adjusted into
IPSSA’s “ideal” range of 7.2 to 7.6, it was found
to drift up to 8.0 or above within three days or less.
As pH affects many other chemical factors, such as oxidation
reduction potential (ORP) and total alkalinity, IPSSA has stated
that weekly service calls are insufficient to keep water chemistry
in balance. According to the organization’s board, the need
for more frequent chemical monitoring and adjustment is
“strongly indicated” by these results.
This finding isn’t entirely unexpected, as many service techs
had noticed an upward pH drift in salt-chlorinated pools. Still,
IPSSA members say they’re surprised at the speed with which
“This pH drift is something we’d suspected for a
while,” said Nathan Smith, director of IPSSA’s Region 6
(Inland Empire, Calif.). “But it’s going to be helpful
for us to have an actual set of scientific data to demonstrate
what’s happening chemically.”
The NPIRC, located at California Polytechnic State University in
San Luis Obispo, was founded in 2004 to provide a scientific
environment for testing pool chemistry. Though the center was
launched by a partnership between Cal Poly and the National
Plasterers Council, the NPIRC board is comprised of professionals
from all segments of the industry.
IPSSA has been supportive of the research center for years, but
this study marks the first time the organization has commissioned a
specific research program. With sufficient funding and member
interest, however, the organization’s board hopes to make
this the first of many studies that will help service techs in the