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Water Balance / Water Conditioning
Water balance is extremely important to pools and spas both.
Balanced water affects many different aspects of water chemistry, some obvious
some not so obvious. For example; water out of balance can affect the pool or
spa equipment with corrosive or basic water, pitting of concrete, etching of
metal surfaces, how much a vinyl liner expands causing wrinkles, it can even
have a drastic effect on how efficiently a sanitizer works at disinfecting water
from bacteria. Other factors it plays upon that are more noticeable like water
clarity or pH bounce.
Water balance consists of pH, Alkalinity, Temperature, Calcium
and Total Dissolved Solids. All of which will be discussed below.
At ordinary pool water temperatures hovering around 75-85
degrees F., temperature is not a major factor in balancing water. Only in the
extremes of spa water, (at 104 degrees F.), or pool water in a winterized pool
(less than 40 degrees F.) does temperature become a factor. The higher the
temperature of water the greater the tendency to cause scaling. Just the
opposite for cold water, the colder the water is, the more likely it is to
corrode than the standard 75-85 degree F. pool water.
Take note that a winterized pool that is kept circulating in the
winter should have the pH kept up around 7.8-80. As for scaling in the hot water
of a spa, keeping the total dissolved solids down (which cause white salt
deposits where water has dried up) and calcium hardness at or below recommended
levels with frequent water changes. If calcium is use or added in a hot tub, the
pH of the water should be kept closer to 7.4 than 7.6. A close eye on the
calcium levels from getting too high is very important in hot tubs to prevent
scaling.
The term "pH" is a scale of measurement to tell us how
acidic (corrosive) or basic (alkaline) the water is. It essentially ranges from
0 to 14, although the extremes of 0 or 14 are never experienced with pool water.
pH of 7 is neutral, that is, the water is not acidic nor is it a base. The ideal
range for a pool or hot tub is 7.4 - 7.6, slightly on the base side which
assists with bather comfort, as the pH of the human eye is about 7.5.
Low pH causes; corrosive water, pitting of concrete, metals
dissolve and staining of pool or spa walls. It also affects or increases;
chlorine loss, vinyl wrinkles, skin and eye irritation.
High pH causes; Scaling water, mineral precipitate out of the water (namely
calcium, copper, iron etc...), plugged filters, cloudy water, reduced
circulation. It also affects or increases chlorine inefficiency along with skin
and eye irritation.
History of pH:
pH was introduced by a Danish biochemist Soren Peter Lauritz Sorensen in 1909 to
measure the acidity of water in the brewing of beer. "pH" stands for
"potens hydrogen," Latin for "hydrogen power" as acidity is
caused by a predominance of hydrogen ions (H+).
Technical information on pH:
pH is the negative logarithm of the molar concentration of hydrogen ions(H+): pH
= -log(H+)/= 10 pH
Each pH unit downward represents, therefore, a tenfold increase in the H+
concentration. A pH of 3, for example, indicates a 10-3 molar concentration of
hydrogen ions. To put it simply the pH scale is logarithmic, meaning that every
pH unit means "10 times". Therefore a pH of 6 is 10 times more acidic
than a pH of 7, and a pH of 3 is 1000 times more acidic than 6 and 10,000 times
more acidic than 7.
How to adjust pH;
When conditioning your water it is always best to adjust alkalinity first,
calcium hardness second (if desired or used) and finally the pH.
Amounts of chemical vary due to such things as buffering effect of the
alkalinity of the water etc...However most containers do give a guideline
amounts to use, based on a correct water balance and alkalinity. If still unsure
then consult your local dealer.
To increase pH use soda ash (sodium carbonate) or caustic soda (sodium
hydroxide), to name a few. Increasing pH using baking soda (sodium bicarbonate)
is not recommended as this also increases alkalinity which may not need to be
raised, but can be done if your careful.
To decrease your pH use muriatic acid (HCl - hydrochloric
acid), or by using dry acid (sodium bisulfate) to name a few.
Note Muriatic acid is used to both lower pH and Total
Alkalinity. The technique of adding this acid determines which will occur.
To maximize the lowering of the alkalinity and minimize the pH drop, slug
the acid, i.e. pour the acid in columns into the water.
To maximize the pH drop and minimize the alkalinity drop, the acid should be
walked, i.e., spread about the pools surface as much as possible.
Total amount of acid given from the tables must be applied over time to avoid
low pH. Initially slug 40%, 25%, 15%, and then the final 15%, waiting a few days
between each addition to allow for pH recovery.
Total alkalinity is the measure of the amount of alkaline salts
in the water, which give water the ability to resist changes in pH or buffer the
water from wild pH swings. In water that contains no buffering ability, the pH
can wander dramatically with the addition of small amounts of acids or bases
(alkali), or other pH altering agents like chlorine or bromine.
If the alkalinity is in the proper range (80-120 parts per
million), the pH will hold steady and pH bounce will be eliminated. However if
the alkalinity is to high, the pH levels may drift up into higher levels,
leading to scaling water conditions or make it to difficult to adjust the pH.
When conditioning your water it is always best to adjust alkalinity first,
calcium hardness (if desired, or used) second and finally the pH.
How to adjust Alkalinity:
Because of the massive amount of information required to list brand names and
concentrations of different products, we are going to use common chemical names
and common concentrations. Your dealer should know or at least be able to find
out the product type and concentrations if they are not marked on the label of
your chemical containers for you. To adjust and compensate for different
concentrations use this formula:
example- you determine from the following chart, that you require 3.2 qts.
of muriatic acid (at 31.45%) is needed to reduce your alkalinity level by 20
ppm. However by checking the label on the bottle, it shows that the
concentration is 27%, a 14% decrease. To determine how much muriatic acid you'll
need, follow the formula below.
Concentration listed here, divided by the label concentration, multiplied by
the amount of chemical recommended here, will equal the adjusted treatment
value.
31.45 / 27 X 3.20 = 3.73 qts. of muriatic acid at 27%
concentration is required.
To increase the Alkalinity use Baking Soda (sodium bicarbonate
100%).
The top line of the following chart is US Gallons being
adjusted.
The second line is how much sodium bicarbonate is required to raise the
alkalinity by 10 ppm. Note there are 16 oz. in 1 lb.
To Raise Alkalinity by 10 ppm (imperial)
|
400 gallons
|
1000
|
5000
|
10,000
|
20,000
|
50,000
|
100,000
|
|
.9 oz.
|
2.24 oz.
|
11.2 oz.
|
1.4 lbs.
|
2.8 lbs.
|
7 lbs.
|
14 lbs.
|
Multiply the above measures by 1/10 the number of ppm
raise required. For example you need to raise a 25,000 gallon of pool
water 25 ppm-: (5000 gallons = 11.2 oz) + (20,000 gallons = 2.8 lbs or
44.8 oz.) = a total of 56 oz. (or 3.5 lbs) to raise 10 ppm, 3.5 lbs. X
2.5 (remember 1/10 of 25 ppm = 2.5) = 8.75 lbs sodium bicarbonate to
raise 25,000 gallons, 25 ppm. Remember to convert oz. to lbs. as
necessary.
The top line of the following chart is metric liters being adjusted.
The second line is how much sodium bicarbonate is required to raise
the alkalinity by 10 ppm. Note there are 1000 grams in 1 kilogram.
To raise Alkalinity 10 ppm (metric)
|
2000 l.
|
4000 l.
|
20,000 l.
|
40,000 l.
|
80,000 l.
|
100,000 l.
|
400,000 l.
|
|
33.6 g.
|
67.1 g.
|
336 g.
|
671 g.
|
1.34.kg
|
1.68 kg.
|
6.71 kg.
|
Multiply the above measures by 1/10 the number of ppm
raise required. For example if you need to raise a 44,000 litres of
pool water 40 ppm-: (4000 litres = 67.1 g) + (40,000 litres = 671 g) =
a total of 738.1 g. (or .7381 kg.) to raise 10 ppm, .738 kg. X 4.0
(remember 1/10 of 40 ppm = 4.0) = 2.95 kg. sodium bicarbonate to raise
44,000 litres, 40 ppm. Remember to convert grams to kilograms as
necessary.
To decrease the alkalinity using Muriatic Acid (HCl).
Note Muriatic acid is used to both
lower pH and Total Alkalinity. The technique of adding this acid
determines which will occur.
To maximize the lowering of the alkalinity and minimize the pH drop, slug
the acid, i.e. pour the acid in columns into the water.
To maximize the pH drop and minimize the alkalinity drop, the acid
should be walked, i.e., spread about the pools surface as much as
possible.
Total amount of acid given from the tables must be applied over time
to avoid low pH. Initially slug 40%, 25%, 15%, and then the final 15%,
waiting a few days between each addition to allow for pH recovery.
The top line of the following chart is US Gallons
being adjusted.
The second line is how much muriatic acid at 31.45%, is required to
lower the alkalinity by 10 ppm. Note there are 16 fluid ounces in 1
pint, and 32 fl.oz. in a 1 quart, and 128 fl.oz. in 1 gallon.= 8
pts./gallon, 4 qts/gallon.
Muriatic required to Decrease Alkalinity 10 ppm
(imperial)
|
400 gallons
|
1000
|
5000
|
10,000
|
20,000
|
50,000
|
100,000
|
|
1.02 fl.oz.
|
2.56 fl.oz.
|
12.8 fl.oz.
|
1.6 pts.
|
1.6 qts.
|
3.99 qts.
|
2 gallons
|
Use the same formulas as used in "To increase
Alkalinity using Baking Soda" to get the calculations required
for your application. Remember to convert fluid ounces, pints, quarts
and gallons as necessary.
The top line of the following chart is metric litres
being adjusted.
The second line is how much muriatic acid at 31.45%, is required to
lower the alkalinity by 10 ppm. Note there are 1000 milliliters in 1
litre.
Muriatic used to Lower Alkalinity 100 ppm
(metric)
|
2000 l.
|
4000 l.
|
20,000 l.
|
40,000 l.
|
80,000 l.
|
100,000 l.
|
400,000 l
|
|
39.9 ml.
|
79.9 ml.
|
399 ml.
|
799 ml.
|
1.6 l.
|
2.0 l.
|
7.99 l.
|
Use the same formulas as used in "To increase
Alkalinity using Baking Soda" to get the calculations required
for your application. Remember to convert milliliters to litres as
necessary.
To decrease the alkalinity using Dry Acid (Sodium
Bisulfate 93.2%).
The top line of the following chart is US Gallons
being adjusted.
The second line is how much dry acid (sodium bisulfate 93.2%) is
required to lower the alkalinity by 10 ppm. Note there are 16 oz. in 1
lb.
Dry Acid to lower Alkalinity 10 ppm (imperial)
|
400 gallons
|
1000
|
5000
|
10,000
|
20,000
|
50,000
|
100,000
|
|
1.37 oz.
|
3.44 oz.
|
1.07 lbs.
|
2.15 lbs.
|
4.3 lbs.
|
10.7 lbs.
|
21.5 lbs.
|
Use the same formulas as used in "To increase
Alkalinity using Baking Soda" to get the calculations required
for your application. Remember to convert fluid ounces, pints, quarts
and gallons as necessary.
The top line of the following chart is metric litres
being adjusted.
The second line is how much dry acid (sodium bisulfate 93.2%) is
required to lower the alkalinity by 10 ppm. Note there are 1000 grams
in 1 kilogram.
Dry Acid used to Lower Alkalinity 10 ppm
(metric)
|
2000 l.
|
4000 l.
|
20,000 l.
|
40,000 l
|
80,000 l.
|
100,000 l.
|
400,000 l.
|
|
51.5 g.
|
103 g.
|
515 g.
|
1.03 kg.
|
2.06 kg.
|
2.57 kg.
|
10.3 kg.
|
Use the same formulas as used in "To increase
Alkalinity using Baking Soda" to get the calculations required
for your application. Remember to convert milliliters to litres as
necessary.
The following information is based on fact, and my
own personal theories. Use this information at your own discretion as
I will not be liable for any damage or problems that result.
Calcium Hardness for water is controversial. Some dealers say you need
it others say you don't. Based on theory of water chemistry called
"The Langlier Index of Saturation", you need a calcium level
of 150ppm - 300ppm. Soft water is aggressive and will cause pitting and
etching of concrete, grout or plastered surfaces as it seeks to
dissolve calcium into the water from whatever contact source.
However calcium's purpose (in my opinion) is not to
prevent the water from being corrosive (as that is what the pH is
for), but rather to add a temporary level of protection to the
surfaces that come into contact with corrosive water, particularly
heaters, metal fittings and concrete pool surfaces. The way calcium
does this is by leaving a thin calcium film on these surfaces, when
the water balance of pH, alkalinity and calcium is ideal. If your pH
does drop below 7 (ideal is 7.4-7.6) the corrosive water has to first
etch the calcium film off before it can corrode the metal or concrete
surfaces adding a degree of temporary protection to these vulnerable
surfaces.
It should be noted that if the water balance is not
right, for example the pH is to high, then calcium can cause excessive
scaling. This scaly build up starts in the heater and in extreme
condition leaves a chalky residue or scale at the water level and in
the filters as well as causing cloudy water. When this scale builds up
excessively on the heater or in the heat exchangers, then the calcium
acts as an insulator causing the heater to be inefficient or even
worse overheat and burn out on an electric heater, or cause a heat
exchanger meltdown on a gas heater.
There are chemicals that prevent or reduce scaling when your pH goes
up or your calcium levels are to high, but at the same time it reduces
the beneficial effects of the calcium hardness in addition many brands
of water softeners promote foaming with extended use, making you
wonder why you put calcium in, in the first place.
If you do have a concrete pool or spa then I recommend
the careful use of calcium and remember complete water balance is
essential. However I have found no benefit to using calcium hardness
in vinyl pools or spas. If you adjust your alkalinity to 80-120ppm and
keep your pH as close to 7.5 as possible, the spa water is not
corrosive with out calcium, and will do no damage to your equipment.
If you do decide calcium is right for you, be aware that if your pH is
low corrosion can and still will occur. Also keep in mind when using
calcium that a high pH can do plenty of damage as well, where as without
calcium a temporary high pH is much less detrimental
and causes no long term damaging effects.
When conditioning your water it is always best to
adjust alkalinity first, calcium hardness second and finally the pH as
the pH is affected by the amounts of calcium and alkalinity in the
water.
The above information on calcium hardness is my own
personal opinion and is not the opinion of the majority of the pool
and spa industry. Follow the above information with care. I will not
be liable for any damages resulting from or lack of calcium hardness.
If anyone can give me a good argument as to the need
for calcium, I would love to hear it.
How to adjust Calcium Hardness:
Because of the massive amount of information required to list brand
names and concentrations of different products, we are going to use
common chemical names and common concentrations. Your dealer should
know or at least be able to find out the product type and
concentrations if they not marked on the label of your chemical
containers for you. To adjust and compensate for different
concentrations use this formula:
example- you determine that you require 24 pounds of
calcium chloride (at 77%) is needed to increase your calcium hardness
level by 100 ppm. However by checking the label on the bag, it shows
that the concentration is 95%, an 18% increase. To determine how much
calcium chloride you'll need, follow the formula below.
Concentration listed here, divided by the label
concentration, multiplied by the amount of chemical recommended here,
will equal the adjusted treatment value.
77 / 95 X 24.0 = 19.5 pounds of calcium chloride at
95% concentration is required.
To increase the Calcium Hardness using Calcium
Chloride (at 77%). Note: Calcium Carbonate is also commonly used.
The top line of the following chart is US Gallons
being adjusted.
The second line is how much Calcium Chloride is required to raise the calcium
level by 10 ppm. Note there are 16 oz. in 1 lb.
Calcium Chloride to raise Hardness 10 ppm
(imperial)
|
400 gallons
|
1000
|
5000
|
10,000
|
20,000
|
50,000
|
100,000
|
|
.77 oz.
|
1.92 oz.
|
9.61 oz.
|
1.2 lbs.
|
2.4 lbs.
|
6 lbs.
|
12 lbs.
|
Multiply the above measures by 1/10 the number of ppm
raise required. For example you need to raise a 25,000 gallon of pool
water 25 ppm-: (5000 gallons = 9.61 oz) + (20,000 gallons = 2.4 lbs or
38.4 oz.) = a total of 48 oz. (or 3 lbs) to raise 10 ppm, 3 lbs. X 2.5
(remember 1/10 of 25 ppm = 2.5) = 9 lbs Calcium chloride to raise
25,000 gallons, 25 ppm. Remember to convert oz. to lbs. as necessary.
The top line of the following chart is metric litres
being adjusted.
The second line is how much Calcium Chloride is required to raise the
calcium level by 10 ppm. Note there are 1000 grams in 1 kilogram.
Calcium Chloride to Raise Hardness 10 ppm
(metric)
|
2000 l.
|
4000 l.
|
20,000 l.
|
40,000 l.
|
80,000 l.
|
100,000 l.
|
400,000 l.
|
|
28.8 g
|
57.6 g.
|
288 g
|
576 g.
|
1,15 kg.
|
1.44 kg.
|
5.76 kg.
|
Multiply the above measures by 1/10 the number of ppm
raise required. For example you need to raise a 44,000 litres of pool
water 40 ppm-: (4000 litres = 57.6 g) + (40,000 litres = 576 g) = a
total of 633.6 g. (or .6336 kg.) to raise 10 ppm, .6336 kg. X 4.0
(remember 1/10 of 40 ppm = 4.0) = 2.53 kg. Calcium chloride to raise
44,000 litres, 40 ppm. Remember to convert grams to kilograms as
necessary.
To Reduce Calcium Hardness:
It is best to dilute pool or spa water (partially drain and refill)
Tri-Sodium Phosphate (TSP) could be used to precipitate calcium out
of the water, but it is not recommended due to it causes algae bloom
(the phosphates are fertilizer for algae).
But if you are going to try it, these are the
instructions:
For every pound of TSP used, it will bind with 1 pound of calcium for
a total of 2 pounds of material that precipitate and settle to the
bottom of the pool. Then vacuumed to waste, not the filter.
Total dissolved solids (TDS) is a measure of how
"tired" or well used the water has become more accurately it
is also a measure of how many salts are in the water. As more
chemicals are added, the higher the TDS level. High TDS levels
indicates that a partial draining and addition of fresh water (of a
lower TDS value or level) is required to reduce the continued high
readings. All other factors being equal, high TDS in water have an
increased tendency for the water to cause corrosion even at pH levels
that are ideal. Most pools/spa water has a TDS less than 2000 ppm,
which has little effect on water balance. As spa water in particular
ages and chemicals are continually added, the TDS does become a
factor, hence the reason spas need to be drained frequently. The more
you use your tub, the more chemicals that are required and the more
frequently the water should be drained and refilled or at least
diluted. Also as the TDS build up in the water they can displace the
calcium hardness in the water slowly making the water soft.
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