WATER MAINTENANCE
The primary reason for
treating pool and spa water with sanitizing chemicals is to
prevent the growth of bacteria which would make swimmers and
bathers sick.
These bacteria can cause infections in ears, nose and throat
and possibly other more dangerous diseases like Meningitis.
Bacterial control is easily accomplished by adding a sanitizer
(most commonly Hypochlorous Acid or simply Chlorine)
regularly, and then passing the water through a filter to
remove the dead bacteria. You then need to be sure that any
additional bacteria entering the pool, is met by a sanitizer
residual in sufficient concentration to kill this new bacteria
as soon as possible.
The primary source of bacteria is the swimmers and bathers
themselves. Animals can also contribute significantly to
bacteria levels. A large dog may contaminate up to twenty
times the volume of water that a human can.
While this all sounds pretty gruesome, it is generally
accepted that most harmfull bacteria will be killed when
exposed to a free chlorine residual as low as one milligram
per litre or in other words one part per million (ppm). By
regularly testing the water and adding the required amount of
chlorine to the pool, a residual level of 1.0 or 2.0 ppm is
easily maintained.
Water Balance
Untreated, or
improperly treated water can be a health threat. Chemically
balanced and sanitized water, on the other hand, will provide
a healthy and visually appealing environment for you, your
family and friends.
Balanced water means that chemical demands have been met. If
the chemical levels are too low the water will aggressively
seek the products it needs by attacking the pool surface and
equipment. This may lead to severe corrosion problems. On the
other hand, high chemical levels may lead to the formation of
scale on the pool surfaces and equipment. Out of balance water
can, therefore, cause expensive damage to the pool and may
also inhibit the sanitizing process. In simple terms, the pool
owner should balance the following variables :
pH
Total alkalinity
Clacium hardness
pH
pH is a measure of how
acidic or alkaline the water is. The pH scale ranges from 0 to
14, with 7.0 being neutral. values below 7.0 are acidic, and
values above 7.0 are alkaline. With pool water we are seeking
a pH balance suitable to the pool user, the pool, and
sanitizer used. Australian Standard 3633 defines the operating
range as 7.0 to 7.8 and the recommended range of 7.2 to 7.6 (SPASA
recommend 7.0 to 7.2 for fibreglass pools). Topping up your
pool, heavy rain, heavy bathing loads and chemical additions
can all change the pH level of your pool water. Incorrect pH
levels can have the following effects : Cause swimmer
discomfort (itchy skin, red eyes, etc.) Interfere with the
action of your pool sanitizer. Effective sanitizing relies on
pH values. Therefore, sanitizer and pH levels, should be the
measures you check and adjust most often. Regardless of the
chlorine type or the chlorination process used, any pH drift
above the recommended range(7.0 to 7.8) will inhibit the
sanitizing effect of your chlorine.
Total Alkalinity (T.A.)
This is a measure of
bi-carbonates, carbonates and hydroxides in your water. The
Standard recommends a range of 60 to 200 parts per million (ppm).
Your pool builder or pool shop will advise you of the
recommended level for your pool. Low T.A. will lead to erosion
of the surface of concrete and painted pools. It will also
cause the pH levels to be very unstable with small additions
of chemicals resulting in major shifts in pH. This is
sometimes known as "pH bounce". Total Alkalinity can be
changed in the following ways : Adding buffer (bi-carbonate of
soda). This raises the Total Alkalinity. Adding acid to your
pool to lower pH will also lower Total Alkalinity. Topping-up
your pool will change the Total Alkalinity depending on the
T.A. of the top-up water. It can be seen that acids will lower
the pH and Total Alkalinity. There is an interconnection
between these two chemical components and, because of this,
they need to be adjusted together. The levels you are seeking
to maintain are : pH of 7.2 to 7.8 (7.0 to 7.2 - fibreglass
pools) Total Alkalinity of approx. 100 to 120 ppm (60-200 is
the recommended range). Check with you pool builder or
poolshop for the level required in you pool. Lets assume that
the pH is OK but the Total Alkalinity is low. To raise the
level, add "buffer" (Sodium Bicarbonate) at the required rate.
However, Buffer is an alkali and will also raise pH. Acid
(Hydrochloric Acid or Sodium Bisulphate), which is used to
lower pH, also lowers T.A. the trick is therefore to raise the
T.A. artificially high so that when acid is added, to lower
the pH to the correct level , the T.A. is also reduced to the
correct range. Note : Hydrochloric Acid must always be diluted
(one part acid to ten parts of water) prior to adding to the
pool. Always add acid to water, never water to acid.
Calcium Hardness
In simple terms, this
measures the amount of dissolved calcium in your pool water.
The recommended range is 80 to 500 ppm. Both Total Alkalinity
and Calcium Hardness need to be brought into balance. If not,
low levels will mean the water is corrosive to the pool and/or
equipment; high levels will lead to scale formation on pool
and equipment. Calcium Hardness tests cannot usually be
performed with the standard test kit. We suggest a water
sample be taken to an NSPI Accredited Pool Shop for testing. A
rough rule of thumb in areas where calcium levels are not
naturally high is that testing annually will suffice after the
initial adjustment. The only qualification to this is if you
are using Clacium Hypochlorite to sanitize your pool. This
chemical raises Calcium Hardness levels which may require more
frequent testing and adjustment.
Tip....When adding chemicals it
is best to add small quantities, leave for a few hours and
re-test. Adding large quantities can result in big problems
and big expense.
Types of Chlorine
Chlorine is available
in a number of different forms. Granular, liquid or tablet,
and can also be stabilized or unstabilized (Stabilizing refers
to the combining of isocyanuric acid with chlorine to protect
it from UV rays, which drastically reduce it's effectiveness).
Chlorine can also be generated by a Salt Chlorinator. Each of
these different forms has it's own features and benefits. For
instance, granular chlorine is convenient, easy to store and
relatively cheap, however it cannot be dosed automatically. On
the other hand, liquid chlorine is bulky and can't be stored
for long periods, but can be dosed automatically. All are
satisfactory sanitisers for your pool, so choose the one that
best suits your budget and lifestyle. No matter which form you
decide to use, the requirement for a residual of 1.0 to 2.0
ppm remains the same.
Tip..Never mix
different types of chlorine, fire and/or explosion can result |
