Water Talk By: Kelley and Susan McGuiness

Water Chemistry made simple, or at least as simple as possible

Pool and Spa Chemistry and Water Balance.  Pools and spas are great, but they can become your worst nightmare if the water chemistry isn't up to snuff.  Browse around for the information you need and if you have any questions please feel free to E Mail us and we will try to help.

Our Spa Service Company

Pool and Spa Facts.  This is a new section and we hope it will help answer your questions and help others.  We take your E Mails or queries in the search engines and try to answer the question in this Faq area.

VGBA Regulations and what you need to know.  Please read this, as, this is very important

VGBA Regulations

Why these regulations are now Federal Law

It appears that this law is only for commercial pools and not residential pools.  This really angers me as this incidence happened in a private pool, and at this point operators of commercial facilities spend thousands to upgrade.  I agree with the upgrade but it is my wish to have all residential pools inspected and upgraded.  If you have a pool that has a single bottom drain, this could happen to you.  Get it Fixed!!!!!



Quick Links

TDS     TDS Part 2     PH     Testing the Chlorine   

Total Alkalinity   Calcium Hardness

  Stabilizer (Conditioner) 

Copper, Iron, and Others  

Flocculation in Pool Water  

Water Born Pool Illness

This is the most important area of spa maintenance.  It can happen in a day or not for a year, but when it happens, it can get ugly.  Change your spa water often.  If your water appears milky, or you cough while in the water, change it.


Let's tackle the why question first: The most common reason for draining a spa is because the amount of total dissolved solids in the water has reached its maximum allowable level. As a general guideline, spas should be drained when the TDS level reaches 2,000 to 3,000 parts per million or 1,500 ppm above the start-up TDS level.
By definition, TDS is absolutely everything dissolved in the water - from metals to chlorine to bromine, alkalinity, salts, bather waste and more. And when the amount of these substances in the water gets too high, it can cause a number of problems, including salty-tasting water, colored but clear water, algae growth, metal corrosion, cloudy water, eye and skin irritation, false test readings, coughing, and black mold. 

What causes TDS levels to increase? When water is heated, aerated and agitated - as is the case with water in spas - the water's evaporation rate increases significantly. This, in turn, dramatically affects the TDS levels in spa water because only the water evaporates; anything else that may have been dissolved in the water gets left behind.
As the water level in a spa drops, the first prescribed action is to add make-up water. But while this water will have a relatively low TDS level, it too will evaporate eventually, adding its share of TDS to the remaining water in the spa. As this cycle continues, the spa water's TDS levels will continue to climb.
TDS levels are also increased whenever the spa water is treated chemically. For example, adding as little as 1 pound of dichlor, trichlor or bromine tablets to 500 gallons of water can create an increase of 240 ppm to the water's TDS level.
And it does not take long for that much dichlor to be added to the spa: In addition to the 1 to 2 ounces of dichlor needed for regular chlorination each week, many owners use their spas two or three times a week, each time adding another ounce of dichlor. At this rate, it would only take three weeks or so to raise the TDS levels by 240 ppm.
Many other common spa products also contribute to a spa's TDS count, including algaecides, algae preventers, acid, sodium bicarbonate, clarifiers, scale inhibitors, foam suppressants, stain inhibitors and nonchlorine shocks.
For example, if a spa owner adds a 2 ounce dose of a nonchlorine shock to the water after each use, that dose alone will produce about 28 ppm of TDS in a 500-gallon spa.
Another contributing factor here is bather waste. just 3 pints of human sweat can produce approximately 4 grams of salt, which would add approximately 2 ppm to the TDS of a 500-gallon spa. In the case of a commercial spa that may handle an average of 25 bathers a day, the amount of TDS from human sweat alone could be as much as 50 ppm every day.
And don't forget, bathers also bring with them residual soap, deodorant, hair spray, suntan lotion, body oil, hair gel, laundry detergent, hand lotion, cosmetics and other personal-care substances - all of which can contribute to the build up of TDS.
When you consider the possible factors that could contribute to the spa water's TDS, it's easy to see how the TDS level can climb very quickly and why frequent draining is needed.
Now, as to how often a spa should be drained, the National Spa & Pool Institute suggests the following formula: One-third of the spa's gallonage divided by the average daily bather load equals the number of days that the water can be used.

(Gallons x .33) -- bather load = days of use

For example, a 1,200-gallon commercial spa with an average bather load of 25 people a day should be drained after 16 days of use:

(1,200 gallons x.33) - 25 people = 16 days of use

For residential spas, however, most experts would agree that draining a residential spa every three months is Necessary.

Signs that may tell you that your spa has TDS.  One sign is that you are constantly reading low alkalinity and adding A+ every week.  Another good sign is a milky look to the water, especially when you turn the air on to your spa.  I have found also that a sudden and incurable development of black mold on the cover , behind the pillows, and around the controls.  And one final sign, and this is after it has gone to far is that you find yourself coughing when you are in the spa.  If you are experiencing any of this change the water, it's better to change your water too often than not enough.

Pool & Spa water pH

The pH is one of the most important factors in pool water balance and it should be tested and corrected at least every week. pH is the measure of how acid/ alkaline the swimming pool water is. A pH of 7.0 is neutral - below 7.0 is acidic, above 7.0 is alkaline. The pH of our eyes is 7.2 . No wonder that the ideal pH for your pool is just that - 7.2 , and should be kept within the range of 7.0-7.6 .

What happens when the pool is too acidic?
(pH is low)

  • If your swimming pool is Marbelite or plaster, the pool water will begin to dissolve the surface, creating a roughness which is ideal for pool algae growth. A similar result occurs in the grouting of tiled swimming pools.

  • Metals corrode - and this includes swimming pool equipment, pipe fittings, pump connections, etc.

  • As the swimming pool walls and metal parts corrode, sulphates are formed. These sulphates are released from the water onto the walls and floor of the swimming pool causing ugly brown and black stains.

  • Chlorine, which is used as a disinfectant in the swimming pool water, is activated and lost to the atmosphere very quickly. The water is not being sanitized, and we are throwing away our money by adding chlorine when the pH is too low.

  • When we swim, our eyes and nose burn. Our swimwear fades and perishes. Our skin gets dry and itchy.

What happens when the pool is too alkaline?
(pH is high)

  • The calcium in the swimming pool water combines with carbonates and forms scale, just like in our kettles. This calcification is seen most at the waterline, where it traps dust and dirt, turning black with time.

  • The swimming pool water starts to become cloudy or murky and it loses its sparkle.

  • The calcium carbonate has a tendency to plate out on the sand in the swimming pool filter, effectively turning it into cement. So your sand filter becomes a cement filter, and loses its ability to trap dirt from the pool water.

  • As the pH rises, the power of the chlorine to act on foreign particles is lost. At a pH of 8.0 the pool can only use 20% of the chlorine you put in. So 80% of it goes to waste and you would need 5 times as much chlorine to provide the disinfection you need.

  • In alkaline swimming pool water, the swimmers suffer too. Our eyes and nose burn and our skin gets dry and itchy.

By neglecting to test and correct the pH of swimming pool water, we not only cause it to become unsightly, but we also cause ourselves physical discomfort. In addition to this, we insist on throwing away our hard-earned money on swimming pool chemicals that cannot possibly be effective in that pool water.

After testing the water, the necessary chemicals must be added to bring the pH to a level of about 7.6

Testing the chlorine

We recommend the Taylor Complete High test kit Part # K2005

When planning to buy a test kit to measure the chlorine levels in your pool, it is important to remember that there a 3 aspects which can be measured:

  1. Free available chlorine (or residual chlorine) - is the amount of chlorine in the pool that can sanitize or disinfect the water and is the important measurement for us.

  2. Combined chlorine - consists of undesirable, bad-smelling, irritating compounds which form when there isn't enough free available chlorine.

  3. Total chlorine - is the total amount of chlorine in the water. It includes both free available and combined chlorine.

We are interested in how much available chlorine there is in the water - chlorine that can act on foreign substances in the water to keep the pool clean and safe for the swimmers.

Too little chlorine results in algal and bacterial growth, waterborne illnesses, cloudy water and insufficient sanitation of the water.

Too much chlorine can result in eye, nose and skin irritations. Remember, too, that the chlorine in the pool is carcinogenic and we should aim to keep its level to the minimum required for complete disinfection.

Test kits which use tablets rather than liquid reagents are preferred. The tablets are easier to use and provide more accurate results. Also make sure that the chlorine measuring tablets are "DPD" as only these can measure the free available chlorine.

Take the water sample from at least 20-30 cm below the surface and at least that far from the wall of the pool. Test the water according to the test kit's instructions.

The desirable level of available chlorine in the pool is 1.0-3.0ppm with 2.0ppm being the recommended ideal.

Add chlorine according to the test results. As a rough guide, a pool needs about 600 grams of granular chlorine (2-3 cups) for each 13,000 Gal of water twice a week during the hot swimming season (150 grams or 1/2-3/4 cup if using a Nature 2 cartridge). Please note that this is only a guide, and actual chlorine requirements can only be determined by regular testing.

Total Alkalinity

The total alkalinity (TA) is a measure of how much of the alkaline substances there are in the water. In the swimming pool water, we are concerned with bicarbonate alkalinity, which should be between 80 ppm and 120 ppm.

When the total alkalinity (TA) is within this range, it prevents rapid pH changes and "stabilizes" the pH level.

If the TA is too low, Marbelite and plaster walls will become etched, metals corrode, the pool's walls and floor can stain, the water can turn green, eyes burn and we can have pH bounce (pH rapidly going up and down, seemingly at random).

If the TA is too high, the pH is difficult to adjust, the water becomes cloudy, the pool constantly needs acid (according to your test kit) and the chlorine loses its efficiency as a disinfectant.

It is recommended that you test the TA regularly, but in practice it changes very little in a well-maintained pool.

To raise the level of TA, we use sodium bicarbonate; it is the only chemical which will do this without increasing the pH very much. Use the calculator to find out how much sodium bicarbonate you need to raise the TA of your pool. Note that you should only add sodium bicarbonate at the rate of 1 kg per 13,000 gals of water every 4 days. Raising the TA can therefore be quite a time-consuming, slow process.

Lowering the total alkalinity is also a slow process. Acid, either liquid or dry, is added to the deepest part of the pool with the filter off. The acid should only be added a little at a time, diluting it before pouring it into the pool. Wait 3 days between applications. It could take days or even weeks to reduce the TA if it is very high. You should consult a pool professional if you have a high TA.  The quantities of hydrochloric acid and dry acid you will need can be calculated using pool calculators.

Calcium hardness

Total hardness in the context of pool water refers to the total mineral content of the water. This is made up of calcium, magnesium, iron, manganese and other elements. These elements are present in the water used to fill the pool, and the levels can increase through the use of regular pool chemicals (e.g. chlorine composed of calcium hypochlorite). We are interested in the calcium hardness levels.

The ideal range for calcium hardness is 250-350 ppm.

If the calcium hardness is too low, the water becomes corrosive and results in the etching of the pool's surfaces. Metals corrode - and this includes pool equipment, pipe fittings and pump connections. As a result, the pool's walls and floor can stain.

Low calcium hardness can easily be increased using calcium chloride. The amount needed can be calculated using the calcium chloride calculator.
NOTE: divide the required amount of calcium chloride into 3 parts. Add the first part and circulate the water for at least 4 hours. Test the water again and repeat the process until the desired level is reached.

If the calcium hardness is too high, the result will be scale formation on all pool surfaces. The filter and pipes become clogged, reducing water flow and filtration efficiency. The water becomes cloudy and swimmers complain of eye irritations.

Reducing calcium hardness is very difficult. Either replace some or all of the water in the pool, or add chemicals that will keep the calcium in solution and prevent it from depositing out. If the calcium hardness is high, we recommend that you consult a pool professional.

Total Dissolved Solids

Total dissolved solids (TDS) is, as its name implies, the measure of the total amount of dissolved material in the water.

The level of TDS in the pool is influenced by many factors; the chemicals we add to adjust the pH, chlorine, water hardness, alkalinity, dust, dirt, human waste, . . . all increase its level.

The maximum acceptable level of TDS for swimming pools is 1,500 ppm. At values above this, we begin to notice stains in the pool. It will also reduce the activity of any chemicals you add, preventing them from doing what they're supposed to. The water may also become cloudy.

Unfortunately, if the TDS level is too high, there is little that can be done to reduce it. The only practical solution is to drain some or all of the water from the pool (depending on how high the TDS is), and replace it with fresh water (with a low TDS). A regular backwashing routine will help to prevent the TDS from rising too much.

Stabilizer (conditioner)

Chlorine, which we use as a sanitizer in our pools, is very unstable. The effects of the sun's UV rays and high temperatures reduces chlorine's effectiveness and breaks it down into inactive components.

Stabilizer, or cyanuric acid, is a compound which protects the chlorine from the negative effects of UV and heat. It not only ensures that our pool remains clean and safe for the swimmers throughout the day, but it also reduces the amount of chlorine we need to add in order to maintain these levels of disinfection.

"According to research results, pools without stabilizer lose about 90% of their total chlorine residual on a sunny day in two or three hours. Pools treated with 25 to 50 milligrams per liter of cyanuric acid, however, under the same conditions, lose only 10 to 15 percent of their total chlorine.

Ideally, the stabilizer should be maintained at a level of about 50 ppm, the acceptable limits being 40-80 ppm. If you use a stabilized chlorine product, you will need to add very little, if any, stabilizer. To find out how much cyanuric acid your pool requires to raise the level of stabilizer, you can use a stabilizer calculator.

Hot tub and spa owners need not worry about this, as your sanitizer tablets contain their own stabilizer

If the stabilizer exceeds 100 ppm either partially or completely change the water, as there is no way to decrease cyanuric acid

Copper, Iron and others

Copper is one of nature's elements. It is also used in the equipment and plumbing in most swimming pools. Copper, in its free state, may also be present in cheaper algaecides.

Corrosive water (low pH, low TA, low calcium hardness) caused by improper water balance or misuse of chemicals can cause copper to be dissolved into the pool water. The water supply you use for topping up the pool may also contain high levels of copper, iron and other metals.

The maximum level for copper is 1.0ppm, though lower levels are recommended. At high concentrations, the copper deposits out of the water and onto hair, fingernails or pool walls causing green stains. High levels of copper can also cause green water.

Iron in the pool causes the water to turn brown or green. It can also cause staining of the pool walls. Iron has much the same causes as copper (i.e. corrosive water or high levels in the top-up water). The maximum level of iron is 0.3ppm although iron-free water is desirable.

Copper and iron can be "locked" into the water using chemicals (chelating agents). This prevents the metal from discoloring the water or staining the pool.

Magnesium and manganese in the water increase the hardness and can cause scale. See also calcium hardness.


Flocculation in swimming pool water

The clumping together of smaller particles to form larger particals which filter out more quickly.

One of the problems with our easily maintained sand filters is that they are unable to trap dirt or foreign matter below 0.02 mm (20 microns). Cloudy water is probably a result of these minute particles of matter if the total alkalinity, pH, calcium hardness and TDS are all within the recommended limits.

Flocculation (or coagulation) is the process of adding chemicals which bind or stick these tiny particles together, resulting in larger clumps which settle to the bottom of the pool and leave the water clear. These "clumps" can be easily removed by vacuuming the floor of the pool.

Chlorination or chlorine shock treatment may also clear the water, but this is both expensive and upsets the water balance.

Flocculant is relatively inexpensive and can be used frequently in pools that are exposed to high levels of pollutants (both environmental and swimmer waste). Follow the manufacturer's instructions for use, as there is a wide variety of "floc agents" available, each of which has different directions.

Waterborne Pool Illnesses

Swimming pools are exposed bodies of water and are thus subject to contamination. The contamination can be carried into the pool water by the environment (e.g. wind, rain) or by swimmers.

There has been a dramatic increase in infections and infectious diseases from swimming pools over the past few years. Some strains of bacteria and viruses have built up resistance to the chlorine we use as a sanitizer in our swimming pools. Others are destroyed very slowly. Consequently, there has been an increasing demand for alternative sanitizers able to quickly and effectively destroy the disease carrying organisms.

Unfortunately, it is impossible to prevent bacteria and viruses from entering the pool water. In swimming pools with a high swimmer load, the level of contaminants entering the water are especially high. Ill or recovering people are requested to abstain from swimming, but many ignore this plea. Chlorine breaks down very fast in the presence of high contamination and swimmer load and due to the effects of the sun's UV rays and heat. With these factors in mind, many swimming pool maintainers over-chlorinate the pool water in the hope that illness can be prevented.

This creates another dilemma - chlorine, too, can cause health problems and overuse should be avoided at all costs. Mineral water sanitizers such as the Nature 2 can reduce chlorine consumption by 75%, thus creating a safer and healthier swimming environment. The Nature 2 also effectively destroys potentially harmful bacteria, viruses and algae before they can strike, but be aware The Nature 2 process can be very slow, and may not keep up with your usage.

A total reliance on chlorine for swimming pool disinfection is illogical in the light of research results. There is unequivocal proof of the efficacy of non-chlorine additives or pool water treatments that can supplement chlorine to create safer pool water. Elements such as copper and silver have become widely accepted as potent anti-bacterial and anti-viral agents. Patented products like the Nature 2 make good use of this knowledge in producing swimming pool disinfectants able to cope with the micro-organisms that chlorine cannot destroy.

These are some of the diseases that can result from infected pool water:

  • Gastroenteritis, Dysentery, Amoebic dysentery, Cholera, Typhoid, Hepatitis A, Giardiasis, Cryptosporidiosis, Salmonellosis, Shigellosis, Dermatitis.