DPD
The reagent used in test kits to indicate free available chlorine or bromine. DPD turns pink when chlorine or bromine are present. DPD is recommended for chlorine testing. (See OTO)
Disinfect
To Kill and inhibit growth of harmful bacteria and virus in pool water.
Dry Acid
A granular chemical used to lower pH and/or total alkalinity.
Filter
A device that removes undissolved waste particles from the water by recirculating the water through a porous substance, a filter medium or element.
Free Available Chlorine (Chlorine Residual)
That potion of the total chlorine remaining in chlorinated water that is not combined with ammonia or nitrogen compounds and will react chemically with undesirable or pathogenic organisms.
High Total Alkalinity
In many parts of the United States the alkalinity of the water is high (in some cases, as much
as 300-400 PPM) and as a result, the pH of the water tends to remain high (8.2-8.4).
Acid should be added to lower the pH to the desired 7.4-7.6 range. The acid will also destroy
a small amount of the alkalinity. However, within the next 2 to 4 hours, the pH generally
bounces back to above 8.0 because of the high remaining total alkalinity reserve still remaining in the water. Although high total alkalinity indicates there will be a frequent need for acid, never add acid to the pool without first checking the pH and acid demand.
Only by frequent adjustments of pH with acid will alkalinity eventually be lowered to the
proper level. At this point, pH will be more or less "stabilized" and will tned to rise at a
lower rate. Acid then will be needed less frequently and in smaller amounts.
Low Alkalinity
If you live in an area where the alkalinity of the water is abnormally low, the water tends to
be corrosive to the finish of plaster pools. Often pH is too easily lowered below 7.0 and this
may result in corrosion of the metal equipment and plumbing, wrinkling of vinyl liners and
severe eye irritation. If pH and total alkalinity are both low, first increase the total alka
linity to the proper range. Usually this adjustment also brings the pH up to the proper level.
In some areas, pool water has a high pH even though total alkalinity is low. Under these
conditions, you should adjust alkalinity first and then adjust pH. Otherwise, it is difficult
to get pH in the proper range without going over acid.
You can increase alkalinity to the desired 100-125 PPM range with the use of alkalinity
increaser. For every 1.5 pounds of alkalinity increaser to 10,000 gallons of water, alkalinity
is raised 10 PPM.
Non-chlorine Shock
An oxygen based shocking compound. Some non-chlorine shock compounds are fast dissolving and can allow swimming just 15 minutes after use.
Organic Wastes
Wastes such as saliva, urine, perspiration, and suntan oils which swimmers introduce into the pool. Most organic wastes will not filter out and must be removed by shocking.
OTO
A chemical reagent which reacts with total bromine or chlorine and turns yellow. OTO test kits don't easily indicate whether the chlorine or bromine is combined (as chloramines or bromamines) or available. OTO is acceptable for testing bromine, since bromamines are
effective sanitizers, but DPD is recommended for chlorine (See DPD)
pH Control
The term "pH" refers to the acid-alkaline balance of water expressed on a numerical
scale from 0 to 14. A test kit measuring pH balance of your pool water is available
from American Pool Supply. The control of pH is dependent to a large extent upon the
total alkalinity content of the pool water.
Rule: 7.4 to 7.6 is a desirable pH range.
It is essential to maintain the correct pH. If pH becomes too high (over alkaline),
it has effects:
- Greatly lowers the effect of chlorine to destroy bacteria and algae.
- Water becomes cloudy.
- There is more danger of scale formation, on the plaster or in the coils of the heater.
- Filter may become blocked.
If pH is too low (over acid), there may be:
- Excessive eye burn or skin irritation.
- Etching of the plaster.
- Corrosion of metal fixtures in the filtration and recirculation system which may
create brown, blue, green or sometimes almost black stinas on the plaster.
- It destroys the chlorine very rapidly.
*Caution: Do not test for pH without first neutralizing the chlorine in the water sample.Otherwise, the chlorine may interfere with the test to give you a false reading. The DPD Test Kits containing neutralizer will enable you to check pH in the presence of a chlorine residual.
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6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4
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Add Soda Ash...Marginal...Ideal...Marginal...Add Acid...
If your pool water pH is less than 7.2, turn off the pool, recirculation pump temporarily in
order to minimize corrosion in your pool pump, heater, plumbing, etc. Add soda ash as a quick
and simple way to bring the pool water pH back to a safe range. Remember to turn pool pump
back on as you add the stabilizer. Maintain a normal chlorine residual, but do not super
chlorinate for 4-5 days. Check the total alkalinity. If it is low, add sufficient
alkalinity increaser to raise total alkalinity to the proper range and to prevent future
low pH problems.
Phenol Red
A test kit chemical used to measure pH. High bromine concentrations can cause phenol red to turn purple (instead of red) which leads to a false high pH reading. If in doubt about your test kit, consult your dealer.
ppm
Parts per million. A concentration unit used to indicate the trace presence of various chemicals (hardness, sanitizer, or total alkalinity) in pool water. One ppm is the same as one ounce in 7.812 gallons (or 1,000,000 ounces).
Reagents
Standardized chemical used to test various aspects of pool water (pH, bromine/chlorine levels etc.).
Sanitize
To kill undesirable or pathogenic (disease causing) organisms, and having a measurable residual at a level adequate to maintain the desired kill.
Sanitizer
A chemical which disinfects (kills bacteria), kills algae and oxidizes organic matter.
Saturation Index
An equation which uses water temperature, pH , total alkalinity, and calcium hardness to predict if the water is corrosive or scale forming. The saturation index gives
a clear picture of your pool's water balance.
Scale
In hardwater areas, pool water has a high calcium content, so it is necessary to control the
pH and the total alkalinity carefully to prevent scale from forming. Scale is caused by
deposits of calcium salts (usually calcium carbonate) and appears at the tile or water line,
or the coil of the heater or, in a plaster pool, it may form either as sharp raised points or
a discolored massive scale on the plaster surface.
Scale is often brownish in color due to entrapped dirt or iron present in the water. Calcium
deposits can also form in the filter resulting in a rapid pressure build-up even if the filter
has just been backwashed.
The calcium content and total hardness content of the pool increases due to repeated evaporation
of the pool water and addition of refill water. The evaporation rate is increased by high water
temperature and wind. After a period of time it may be necessary to drain the pool and refill
it with fresh water.
It is a good policy to check your pool water for total hardness about 2-3 times a month with a
Water Hardness Test Kit. Monthly tests are advisable for the spa (therapy) pools. The use of
Scale and Stain control can help prevent or delay scaling.
Shock (Also known as superchlorination)
Ridding a pool of organic waste (through oxidation) by the addition of significant quantities of a sanitizer.
Total Alkalinity
Total alkalinity is a measurement of the total amount of alkaline chemicals in the water and
controls pH to a great degree. You can think of it as an alkaline reserve which will tell you
whether or not your pool is in proper balance. It is not the same as pH which refers merely to
the reltive alkalinity-acidity balance. Your pool water's total alkalinity should be in the
100-125 PPM range for easier pH control.
A total alkalinity test is simple to perform, with a test kit. You should test about 3
times a week to be sure it is being maintained. NOTE: If stain and scale prevention chemicals
have been or are being used in the pool, keep total alkalinity about 20 PPM higher than normal.
Total Bromine
The sum of both the free available bromine and combined bromine.
Total Chlorine
The sum of both the free available chlorine and combined chlorine.
Water Hardness
Water hardness is a measurement of the amount of calcium and magnesium in your pool. Generally
about 70-75% of the total hardness of the pool water is calcium. Too much calcium is undesirable because it can cause the formation of calcium scale on the plaster finish or in the coils of a heater and block the filter.
The amount of water hardness tends to increase in a pool due to evaporation and addition of
refill water. The use of calcium hypochlorite also increases the water hardness. Generally when
the water hardness reaches a level of 400 ppm, the pool should be drained and refilled with
fresh water. If the pool cannot be drained conveniently, use Stain and Scale Control to prevent
or delay scaling.
Completely soft water with no hardness is undesirable in a pool because the water tends to be
corrosive. Increase it by the addition of calcium chloride dihydrate. Every 1.25 lb. of this material added to 10,000 gallons of water will increase the hardness 10 PPM. This material is weakly acidic, so you should predissolve it in water before adding it to the pool and check pool pH one hour after making the addition.
If water used to fill a pool has an excessive hardness value, it may be desirable to pass 70-80% of the water through a softener before adding it to the pool. However, do not totally soften pool water.
The water hardness test kit will enable you to determine the amout of hardness in your pool
water and your tap water in just a few minutes. The water hardness test should be performed
every 3 months. ** Calcium Hardness in a plastered pool should be minimum of 200 PPM and no
more than 350 PPM. Vinyl and Fiberglass, painted pools 175 PPM and no more than 275 PPM.
