On Apr 23, 6:19 pm, "Lawrence M. Seldin, CMC, CPC"
buffalo ny: swimming pools require sanitary water. salt is not a
sanitizer. you can use chlorine correctly to sanitize the water
overnight with a shock [high level] dose. you could if desired destroy
the leftover chlorine the next day with an oxygen shock [see your pool
supply store for sodium persulfate or one of its cousins]. this would
eliminate the chlorine (and its benefits) from the water.
this is usually new information to many: properly maintained swimming
pool chlorine levels do not have a (chloramine) smell. a (chloramine)
smell reveals improperly maintained INSUFFICIENT levels of chlorine.
insufficient chlorine makes chloramines that irritate the eyes.
the oxygen shock is the second best shock to chlorine shock.
but also see:
which is quoted here for your convenience but see wikipedia for
constantly updated info:
"Salt Chlorinators: Chlorine may be generated on site, such as in
saltwater pools. A New Zealand device the Aquatech IG450 home pool
saline chlorinator was introduced to the residential swimming pool
industry in 1973 when the first commercially manufactured units for
home use were shown at the 1973 Chicago Trade Fair. In the following
years, many US, Australian and South African companies duplicated the
device, as the process of creating chlorine from saline water - a
natural process that occurs in nature when lightning strikes the ocean
- was not Patentable. This process generates chlorine by low-voltage
electrolysis of dissolved salt (NaCl) using an electrical electrode
incorporated in the pool plumbing, eliminating the requirement of
manually dosing the pool daily with powder chlorine. Chlorine
generators avoid the need for constant handling of dangerous
sanitizing chemicals, and can generate sanitizing power at a lower
cost than equivalent chemicals, but they have a significant up-front
cost for the apparatus and initial salting of the pool. Annual
rainfall contributes to dilution of the pool water, which will require
regular "topping up" with several 50Lb (20Kg) bags of salt for the
average size pool.
Another issue is the production of equal amounts of Sodium Chloride
and Sodium Hydroxide (ph = 14, or Base) which causes the pool water pH
to rise to levels that render the production of useful chlorine HOCl
to levels as low as 15% while the balance of the chlorine produced
converts to OCL. OCl still maintains some bacteriacidal properties,
but is only effective in concentration of 25,000ppm, so in effect is
useless. This dramatic swap occurs in water where the pH is exceeds
8.0. This renders the saline system less effective unless a close
watch is kept on pH levels. Some saline units in production (2007)
have incorporated an acid demand test, and the pH is maintainted at
the correct level by periodic shots of acid into the system. The
downside of these units is the need to store large quantities of
Hydrochloric Acid on the pool site which must be secured for safety if
young children are present.
Early salt chlorinators required 2.0ppm dilution, and this content
gave the pool water a slightly salty, brackish taste, but not as salty
as seawater which is around 20.0ppm. Modern units use far less
salinity - around 0.2ppm to 0.4ppm and the salt cannot be detected by
taste. Pool water that splashes and evaporates, such as on a pool
deck, leaves a salt residue. Being closer to isotonic salinity (0.9%)
than fresh water, saltwater pools have an easier feel on the eyes, and
a touch typically characterized as "silky", not unlike bath salts.
Ionization systems using copper and silver, destroying bacteria and
algae, are optional replacements for chlorine systems. In this method
low amounts of chlorine are necessary to combat algae. The pool water
runs through the ionization cells and is disinfected using a low
electrical current. A control unit can decide how much copper and
silver to release into the pool, reducing manual maintenance. The cost
for such a system is higher than that of a saltwater generator, which
already is much more expensive than the standard chlorine disinfection
systems. This method of pool water sterilization has been banned in
Australia, pending an appeal from the local manufacturers of Ion units.
The salt water pool systems use a chlorine generator in the water path
that extracts the chlorine from the sodium chloride electrically and
it then recombines but while it is free chlorine it sanitizes the
water. You still need to shock the pool but you don't add chlorine in
an ongoing process.
This works at about 5 PPT salt (like contact solution or blood) , the
ocean is 37-38 PPT.
Advantages -- if you have a dependable source of salt water -- One of my
favorite pools was salt-water, at the Shek-O Country Club in Hong Kong.
They drew and exchanged salt water from the South China Sea and IIRC didn't
have to use complicated pool chemistry. Another peculiarity of that pool --
it didn't have a heater, it had a chiller to keep the pool water from
getting too hot in the tropic climate -- Regards --
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