Water Balance
A pool that is "balanced" has proper levels of pH, Total Alkalinity and Calcium Hardness. It may also be defined as water that is neither corrosive or scaling. This concept is derived from the fact that water will dissolve and "hold" minerals until it becomes saturated and cannot hold any more water in solution. When water is considerably less than saturated it is said to be in a corrosive or aggressive condition. When water is over saturated, and can no longer hold the minerals in solution; this is known as a scaling condition. So then, balanced water is that which is neither over or under saturated. The cliché that "water seeks its own level" certainly applies here. Water which is under saturated will attempt to saturate itself by dissolving everything in contact with it in order to build up its content. Water which is over saturated will attempt to throw off some of its content by precipitating minerals out of solution in the form of scale.
WATER
BALANCE
Untreated,
or improperly treated water can be a health threat. Chemically balanced and
sanitised 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 sanitising process.
In
simple terms, the pool owner should balance the following variables:
·
pH
·
Total
alkalinity
·
Calcium
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 sanitiser use. 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 sanitiser.
Effective
sanitising relies on pH values. Therefore, sanitiser 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 sanitising effect of your chlorine.
TOTAL
ALKALINITY (T.A.)
This
is a measure of bi-carbonates, carbonates and hydroxides in your water. The
Australian Standard 3633 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.
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 your pool builder or pool shop for the level required in your 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.
In
simple terms, this measures the amount of dissolved calcium in your pool water.
The recommended range is 80 to 500ppm according to Australian Standard 3633.
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 a S.P.A.S.A. 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 Calcium Hypochlorite to sanitise your pool. This chemical raises Calcium Hardness levels which may require more frequent testing and adjustment.