Chemical Problems

Pool Chemical Problems

All About Algae

Algae is the most common pool water problem only because it is the most visibly obvious one. Algae in itself is not dangerous — in fact, it is the main ingredient in many health supplements and tablets. Algae brings danger in that it converts sunlight into food, releasing wastes that become the feeding grounds for unwanted and harmful bacteria and other micro-organisms.

There are well over 20,000 species of algae, only a few of which are encountered in swimming pool water. Algae is almost constantly entering the pool, and as soon as the sanitizer level drops too low, the algae begins to take hold and multiply. It takes as little as a few hours on a warm sunny day for your sparkling pool to develop an algae problem. The algae “spores” found in the air are from algae that have dried out (at a nearby stream, from a neighbor’s pool, etc.) and become airborne with the breeze.

Types of Pool Algae

Algae in swimming pools is often referred to by its color.

Green Algae

By far the most common and relatively easy to treat.

Yellow/Mustard Algae

Troublesome to treat but also relatively susceptible to treatment.

Black Algae

Can be very difficult to get rid of, especially in plastered pools.

Pink Algae

Not an algae at all, but a fungus called Paecilomyces lilacinus that causes slimy white, pink, or gray colonies.

How to remove algae from pools

  • Shock treat the pool. If you are using chlorine, aim for at least 10ppm free chlorine (10 times the recommended minimum level).
  • Circulate the water round the clock, if possible.
  • Brush the pool and vacuum.
  • Add a commercial algaecide prepared to remove algae types that you have (green, mustard or black) according to the instructions.
  • Repeat brushing and vacuuming daily if possible. Add more chlorine if the level falls below 5ppm.
  • Clean or backwash your filter regularly.

Preventing pool algae

Maintaining proper water balance and minimum sanitizer levels will ensure that any algae spores entering the pool water cannot take hold. Most pools use chlorine, which should be kept at a minimum level of 1.0ppm. Using a mineral system may allow you to keep the free chlorine level at 0.5ppm or lower without the risk of developing an algae problem.

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Total Alkalinity

Total alkalinity is a measure of the total amount of dissolved particles in the water whose pH is higher than 7.0. Total Alkalinity (TA) should usually be kept at 80 – 120 ppm, though in high alkalinity waters this is often hard to achieve without resulting in an abnormally low pH. When your TA is low, the following can occur:

  • Etching of the plaster, marbelite, marcite or tile grouting
  • Corrosion of metal parts (pool heater, steps, scoop pole, etc.)
  • Staining of the pool’s surfaces
  • Green water
  • Burning eyes and itchy skin
  • pH bounce (rapid fluctuations in pH)

Raising low total alkalinity

Sodium bicarbonate (bicarb) will raise the TA without excessively raising the pH. You should try to increase the TA over a period of time, adding a maximum of 1 pound of bicarb for each 6,000 gallons of water. When the TA is too high, the following can occur:
  • pH keeps going up despite regular addition of pH-down
  • Cloudy water
  • Burning eyes and itchy skin
  • Reduced chlorine efficiency resulting in algae growth

Lowering high total alkalinity

To lower a high TA, you should:
  • 1. Turn off the pumps and allowing the water to settle
  • 2. Slowly add the pH-reducer into one spot in the deep end of the pool
  • 3. Allow the chemicals to “burn off” some of the alkalinity for 15–30 minutes
  • 4. Turn the pumps back on and allow the water to mix thoroughly

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Chloramine Problems

Chloramines are the result of insufficient free chlorine and usually result in a strong chlorine odor in and around the swimming pool. Chloramines are formed as a product of nitrogen and active chlorine (hypochlorous acid — HOCl). The nitrogen is most commonly introduced into the pool water as ammonia in the form of sweat and (unfortunately) urine.

Chloramines (combined chlorine) are poor sanitizers and have a gaseous tendency. The presence of chloramines (and dichloramines/trichloramines in particular) cause the following physical symptoms:

  • Red, burning eyes
  • Burning sensation in nose, throat, and lungs
  • Dry, itchy skin and dry hair
  • Breathing difficulty leading to "swimmers' asthma", particularly in young children

In addition to these, the pool has a tendency to discolor, becoming milky or green with algae due to the low sanitizing ability of the combined chlorine.

Testing for combined chlorine in pool water

All good chlorine test kits and pool test strips allow you to determine free chlorine as well as total chlorine. Combined chlorine is calculated from these values as follows: combined chlorine = total chlorine – free chlorine. The combined chlorine value should never exceed 50% of the free chlorine value and should ideally be as close to zero as possible. Some cheaper test kits that use liquid reagents (drops) offer one value for the chlorine test. If the reagent bottle is marked “OTO” then you are only testing total chlorine and should consider a better test kit.

Destroying combined chlorine compounds

A shock treatment using either chlorine or a non-chlorine sanitizer will ensure the destruction of the nitrogen compound combined with the chlorine. The pungent smell disappears and the free chlorine level goes up providing complete sanitization of the pool water.
Chemical Problems 1

Common causes of

Cloudy pool water

Causes of cloudy water is usually the result of one or more of the following:
  • High calcium hardness level
  • High conditioner level
  • High pH
  • Low pH
  • High total alkalinity
  • High level of total dissolved solids
  • Low chlorine level
  • Algae
  • Large volume of microscopic particles in the pool water
  • Filter/filtration problems

How to clear up cloudy water

A few causes of cloudy water:
  • If the problem is conditioner: Partially drain and refill the swimming pool to bring the level down to the maximum of 80ppm or below.
  • If the problem is high pH: Add pH reducer to bring the pH within the range of 7.2 – 7.6
  • If the problem is low pH: Add pH increaser to raise pH to 7.2 – 7.6
  • If the problem is total alkalinity: Reduce the total alkalinity according to the directions at total alkalinity problems.
  • If the problem is total dissolved solids: Reduce the Total Dissolved Solids by partially draining and refilling the swimming pool to bring the level below 1,500ppm.
  • If the problem is the filter or filtration problems: Backwash, wash or clean filter or filter medium. Treat or replace sand, DE or cartridge. Check grids or cartridges for tears. Or better yet… call Aqua-Ducks for advice or help.

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Metals in pool water

Fill or ground water can cause copper, iron, and manganese can find their way into the pool. The copper and iron can also be from metals in accessories like the pump or heater that are corroding due to improper water chemistry.

If the pool’s pH, total alkalinity, or calcium hardness level is low, then the water tends to be corrosive and the “rusting” of metal parts in the pool is greatly increased. Another common source of copper is copper-based algaecides. The cheaper ones often supply copper ions rather than complexes and, if too much is used, will result in green pool water.

If the water changes color after chlorine (or any other oxidizer) is added, the swimming pool water probably contains a metal.

What happens if I have high levels of metals?

How do I know which metal is present in my water?
  • Green pool water usually indicates the presence of copper (more likely) or iron (less likely).
  • Brown pool water usually indicates the presence of iron or, occasionally, copper.
  • Purple or black pool water usually indicates the presence of manganese.
To solve the problem of colored water as a result of metals, there are two general approaches:
Shock the pool to oxidize the metal, which then settles out of solution and looks like rust. The rust can easily be vacuumed out of the pool. Add a sequestering or chelating (ˈkēˌlāt) agent, which forms complexes with the metal and prevents it from being oxidized by the chlorine.

Prevent repeat problems: If the source of the copper or iron cannot be established or if it cannot be avoided, regular addition of a chelating agent or sequestering agent (metal out products) will ensure that any new metal arriving in the pool water will be held in an inactive complex.

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Pool Water ph

One of the biggest parts of pool care is maintaining the chemical balance in your pool. Chemistry is key to keeping your pool clean, as well as making it a safe, pleasant environment for swimming. Chemicals like chlorine are used to keep algae and bacteria under control, while chemicals like muriatic acid keep the pH levels of your pool’s water balanced. You’ll need test strips and a drop kit to check and maintain chlorine and pH levels. It also is important to keep a consistent volume of water in your pool; a lower-than-normal level can make your chemicals too intense and a higher-than-normal level can dilute them and make them ineffective. Improper water levels will also have detrimental effect on filtration and circulation.

The ideal range for pH in swimming pool water is 7.0 – 7.6. The pH of our eyes is typically 7.2 – 7.4. In our experience, if the pH is kept at the same level as that in our eyes, the side-effects of burning red eyes is kept to a minimum. The ability of chlorine to disinfect at this level is also optimal.

What is pH?

High pH in swimming pool water may cause the following problems:
  • Calcium buildup on pool surfaces, waterline and accessories
  • Dull or cloudy pool water
  • Clogging of filter medium or elements
  • Drop in disinfection potential of chlorine resulting in algae growth
  • Burning eyes and nose
  • Dry, itchy skin and scalp

Lowering high pH

Adding an acid to the pool water reduces the pH. The most common chemicals used to reduce high pool water pH are:
  • Muriatic acid — typically 30%-35% liquid hydrochloric acid
  • Sodium bisulfate — granule or powder pH reducer, dry acid
Other acids that have been used in pool water are:
  • sulfuric acid — raises TDS levels and adds sulfates to the pool water
  • nitric acid — highly corrosive but is known to work well
If the Total alkalinity of the pool water is within the recommended parameters of 80 – 120ppm, pH reducer should be added according to the instructions on the container. The acid should usually be added to water and mixed before dosing the pool. The pump should be running when the acid is slowly distributed around the pool. Low pH in swimming pool water may cause one or more of these problems:
  • Eroding of the pool plaster or grouting
  • Corroding of the metal pool accessories (steps, heater, etc.)
  • Staining resulting from metal corrosion
  • Rapid dissipation of chlorine requiring increased dosage
  • Burning eyes and nose
  • Dry, itchy skin and scalp
  • Perishing of swimwear, pool toys and accessories

Raising low pH

Adding a base or alkali raises the pH of the pool water. If the total alkalinity is normal, pH increaser should be added according to the instructions on the container. The active ingredient is usually sodium carbonate. Often low pH is a result of acid rain and occurs after periods of heavy precipitation. The normal tendency of pool water pH is to rise through exposure to wind, sunshine and bathers. The most common cause of consistently low pH is low total alkalinity, which should always be adjusted (with sodium bicarbonate) before trying to increase the pH.

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Total Dissolved Solids

Total Dissolved Solids (TDS) is the measure of the total of all the soluble substances dissolved in the water.

For swimming pools, the maximum recommended TDS level is 1,500 ppm. Values above this can lead to various problems with your pool. Some of the issues include: cloudy pool water, staining of the pool surfaces, scaling, hard water, a salty taste, algae growth and irritated skin and eyes.

In swimming pools using salt-chlorine generators, the large volume of salt added radically increase the TDS level. Sunscreen, sweat, debris and other chemicals also increase the TDS level and create a residue in your pool.

The TDS should be checked once every six months. If the pool water has become saturated with contaminants and the TDS level confirms this, the pool should ideally be drained and refilled with fresh water. There is no method to reduce TDS effectively without replacing some or all of the swimming pool water.

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Calcium Hardness

The measure of all the dissolved minerals such as calcium, magnesium and sodium is known as total hardness. Regarding pool water chemistry, it’s known as calcium hardness. High or low levels of calcium hardness can result in issues, so the recommended level for calcium hardness is 200 – 400 ppm. To find out the hardness of you swimming pool, you will need to perform a calcium hardness test.

You can increase the calcium hardness level by adding calcium chloride. If the swimming pool suffers low hardness due to the low quality of the fill water, calcium hypochlorite should be added. You can perform a calcium hardness test if you suspect insufficient levels.

High calcium hardness results in scale formation on the pool surfaces as well as scaling in the pipes, plumbing and filter. High calcium levels will also cause sore eyes of swimmers.

If the calcium is a result of pool chemicals, draining some or all of the pool water will lower the calcium hardness level. If the cause is the fill water, commercial hardness reducers or chelating agents will bond with the calcium to keep it trapped in solution.