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Water Balance

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Water Balance / Water Conditioning

Main Chemical Menu

Introduction To Water Balance

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.


Temperature

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.

Return to Main Chemical Menu.

pH

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.

Return to Main Chemical Menu.

Total Alkalinity

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.

Return to Main Chemical Menu.

Calcium Hardness

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.

Return to Main Chemical Menu.

Total Dissolved Solids (TDS)

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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