Within the pool and hot tub industry exists
many trades, each having
distinct opportunities,
some apparent, others more discreet.
For instance, our industry professionals
in the construction and tile businesses
are masters at creating the shell and
surface of the pool. They also have
opportunities to create beautiful
tile patterns or even grand mosaics
contributing to the pool’s aesthetic.
Manufacturers of vinyl liners create
the barrier that holds the water in, but
the liners also impart the deep blue
color to the water that we expect to see.
However, all this hard work and beauty
can be obscured, or worse, ruined if the
water quality is poor and water turns
cloudy.
Safety and drowning prevention are
the main and most important reasons
to maintain clear pool water. A cloudy
pool can make it difficult for swimmers
to see beneath the surface which can
lead to collisions and possible life-threatening
injuries. The drowning
hazard from cloudy pool water is due
to the inability to see a distressed
swimmer beneath the surface of the
water from above the surface.
Tragically, there are reported
cases of drownings that occurred in
supervised venues with lifeguards
present. In these cases, the pool was
cloudy, and the victims were not visible
beneath the surface. These situations
should NEVER occur, and pools should
never be open for swimming when the
bottom of the pool is not clearly visible.
Another reason that clear water is
important in swimming pools is the
overall appearance. Whether the pool
is commercial or residential, pool users
expect the water to have an inviting and
pleasant appearance. Water that is hazy,
dingy, or discolored is not appealing or
inviting for swimmers.
Yet another reason water clarity is
important has to do with disinfection.
It is probable that cloudy water could
be due to a lack of proper sanitizer.
Swimmers who enter a cloudy pool
with improper chlorine levels can be
subject to bacterial infections such
as swimmer’s ear or dermatitis. Also,
there is the risk of enteric diseases such
as Giardia, E. coli, and Cryptosporidium
from swimming in a pool that is cloudy
due to lack of sufficient sanitizer.
The turbidity is measured using a
device known as a Nephelometer. This
instrument measures light scattered by
suspended particles in a water sample,
at an angle of 90 degrees from the
path of the incoming light beam. The
amount of light scatter is related to the
amount of turbidity and is expressed as
NTUs. Health departments may allow
pools at peak swimmer load to have 1.0
NTUs; however, the filter system must
be able to return the water clarity to
0.5 NTU within eight hours after peak
swimmer load.
There is a practical means by which
a pool inspector will gauge water clarity.
The inspector will want to clearly see
a sharply defined drain at the deepest
point in the pool from a spot on the
pool deck; the acceptable distance away
from the drain will be determined by
local codes. If the bottom drain cannot
be clearly seen, then the pool will be
immediately closed until water clarity
returns, and the drain can be seen with
high definition.
Circulation and filtration are vital
for the effective removal of micron-sized
matter from the water. To grasp
the scale, a micron is one millionth of
a meter, and a grain of salt measures
around 100 microns. The human
eye can discern particles down to 35
microns. Filters are designed to remove
particulate matter, with different types
offering varying capabilities.
Rapid-rate sand filters, for instance,
can eliminate particles down to
50 microns, while their high-rate
counterparts excel further at eliminating
particles down to 25 microns. Cartridge
filters can typically remove even smaller
particles, between 10 to 20 microns,
while Diatomaceous Earth (D.E.) filters
boast an impressive capacity to remove particles as small as 3 to 5 microns.
The efficiency of the chosen filter
directly impacts water clarity, making it
essential to match filtration capabilities
with the desired level of clarity. If
micron-sized material is allowed to
accumulate, the small particles will
combine by attractive forces, and the
pool will become cloudy. All the water
in a commercial swimming pool must
turnover completely through the system
once every six hours. It takes four
complete turnovers of pool water to get
98% filtered water.
Chemical treatment for water clarity
includes a regular routine of oxidation.
Chlorine shocking or oxidizing with
a potassium monopersulfate (nonchlorine)
oxidizer is necessary to
“burn off” organic material that can
accumulate in the water. Additionally,
the use of ozone and or UV will help
to breakdown and remove particulate
matter such as organics and minerals.
This allows the chlorine to be more
effective at sanitizing as well.
Special products, such as
enzymes, water clarifiers or heavy
flocs, can help the filters to be more
efficient at the removal of smaller
micron-sized matter. As always, follow
the manufacturer’s instructions for
optimal results. Another crucial water
quality parameter that helps control
water clarity is pH. The pH of the
water will affect the solubility of certain
compounds, like calcium carbonate;
higher pH values increase the likelihood
this mineral will precipitate from the
water resulting in a cloudy pool.
Water clarity in swimming pools
is crucial for several reasons. Firstly,
clear water enhances the aesthetic
appeal of the pool, providing a more
enjoyable environment for swimmers.
Additionally, it plays a vital role in
ensuring the safety of individuals by
allowing lifeguards and swimmers
to easily detect potential hazards.
Maintaining proper water balance
is essential for clarity, as it prevents
cloudy water, algae growth, and other
factors that can compromise the overall
quality of the pool water. For knowledge
of industry-accepted standards, refer
to ANSI/APSP/ICC-11 2019 American
National Standard for Water Quality in
Public Pools and Spas1.
REFERENCES
1. ANSI/APSP/ICC-11 2019 American National
Standard for Water Quality in Public Pools
and Spas, Pool & Hot Tub Alliance, 2019,
www.phta.org
2. Pool & Spa Operator Handbook, Pool & Hot
Tub Alliance, 2022, www.phta.org
