Sunday, 6 November 2016


Steps to remove algae in swimming pools

1. Brush the walls and floor of the swimming pool to remove as much of the algae as possible.

    This will greatly reduce the amount of time it takes to kill and clear the algae bloom.

2. Ensure that the pH level is within the range of 7.2 - 7.6. This will ensure that any chlorine

    added will work more efficiently - high pH levels in particular will impair the efficiency of
    the chlorine doing its job.With the pool filter system running, add a chlorine based
    swimming pool shock at the rate of 1.6 kg. per 1,00,000 litres of pool water dosage for
    killing algae. The pool filter system should continue to run 24 hours a day.

3. If the condition of the swimming pool does not significantly improve after 12-24 hours of

    filtering, add a second dose of chlorine pool shock at the increased rate. Repeat this process
    until the algae has been eliminated.

4. Once the algae is dead it will turn a white or grayish color, and it will be suspended in the

    pool water or settle to the floor. When there is no longer any sign of the color green in your
    pool, thoroughly vacuum the swimming pool. It is recommended that you vacuum dead algae
    to waste and not through filter.

5. The pool filter should be backwashed or cleaned to be sure that dead algae is not trapped

     inside the filter. If the filter is not thoroughly cleaned the algae may quickly return.

6. Test and balance all of the pool chemical levels using the following guidelines. Free

    Chlorine: 1-3 ppm, pH: 7.2 – 7.6, Alkalinity: 80 – 120 ppm and Calcium Hardness: 200 –
    350 ppm.

7. Begin adding an algaecide pool chemical on a weekly basis to prevent algae from returning.


  • Pay closer attention to the chlorine level of your swimming pool water in the future. Algae and harmful bacteria are almost immediately destroyed by a free chlorine level of 1 ppm or higher. You have experienced an algae problem because you have not properly maintained the chlorine level, and it was allowed to drop below 1 ppm. Test pool water frequently and make any necessary adjustments for a clean, safe and easy to maintain swimming pool.
  • Chlorine pool shock needs to be dissolved in a large bucket of water before it is added to the swimming pool. Always add chemicals to water when dissolving. NEVER add water to chemicals.
  • Monitor your pool filter system closely during this entire process and thoroughly backwash or clean the filter each time the pressure rises 10 psi. above the normal operating pressure. The dead algae that your pool filter collects may quickly dirty the filter, and need to be cleaned out frequently.
  • Phosphate Levels - high levels of phosphates in pool water will result in your pool using much more chlorine than usual. They are also one of the main food sources for algae, therefore it is important to have these levels checked fairly regularly especially if the pool seems to be using more chlorine than usual. A pool with a particularly bad case uses approximately 2.5 times the amount of chlorine that it should have, making it very difficult to maintain.

  • The swimming pool cannot be used until the algae is dead, and the chlorine level of the pool 
    water has returned to a safe level of 3 ppm or less.

Chlorine and swimming pool algae..

Why does chlorine kill swimming pool algae?

Chlorine kills bacteria and other single-celled algae by a chemical reaction called oxidation, which is 
sort of like burning by acid. Most drinking water also has chlorine, for the same reason. 
Our skin is tough enough that weak chlorine in water won't hurt us, but you've probably noticed that 
in some swimming pools your eyes start to sting if you stay in too long. That's the chlorine starting 
to "burn" them. 
Water, including swimming pool water, contains disease germs. Chlorine is the most common 
sterilizer. Slight amounts of chlorine are used to kill germs, but are harmless to people. Where water 
is sediment-free, only one or two parts of elemental chlorine may be added to 10 million parts of 
Remember that shock, or super chlorination can never do much harm, but the bathing experience 
will be unpleasant until the chlorine drops to its normal level. Under normal conditions, there 
should be NO apparent odour of chlorine; if your pool smells of chlorine, this is due to the chlorine 
that is combined with other stuff and cannot escape - it actually means that there is not enough free 
chlorine in the pool. 
Algae can grow in swimming pools if nutrients are present and a sufficient level of free chlorine is 
not maintained. In addition to properly dosing your water, it is recommended that the algaecide be 
added in the morning on a bright sunny day for best results. Algae are plants and grow in the 
presence of sunlight. Adding algaecide during algae's best growth time will increase intake of the 
algaecide and make it more effective.

Green Algae - is very susceptible to chemical treatment. Superchlorinate with 10 to 20 ppm
chlorine in the evening. Keep the filter running and brush the pool walls and bottom. Periodically 

check chlorine and maintain above 3 ppm until water clears. Using an 



quaternary ammonia the next morning will help prevent the return of green algae.

Mustard Algae - is much more resistant to chemical treatment and clings more tightly to pool walls 

than green algae. Adjust pH and super chlorinate as for green algae then brush carefully. Later 

vacuum the pool, check chlorine and super chlorinate again if necessary. Mustard algae will 

generally return unless treated with a special mustard 


 or a copper based (CuSo4) algicidal. 

Algicide should be added in the morning to treat algae in daylight - its most active period.

Black Algae - can be controlled to some extent by frequent superchlorination and careful brushing 

with a stiff brush. (You should have a wire-brush attachment for your telescopic pole). Spot 

treatments can be made by turning off the recirculation pumps and pouring granular chlorine 

directly on recently brushed spots. You need to use strong algicides and maintenance of relatively 

high free-chlorine residual, but complete removal of black algae may require draining and cleaning 

the pool.

A very good "shock" for an algae bloom is liquid chlorine - it is cheaps, works quickly, will not
harm the pool surface. It also breaks down into plain water in 1-2 days, leaving no residuals. Be
sure to also algea brush your pool daily to eliminate spores on the pool wall 
(which chlorine cannot 


How to Diagnose and Clear Cloudy Swimming pool Water

1. Test the swimming pool water for Combined Chlorine, pH, Alkalinity and Calcium
Hardness. The two areas that are most likely to cause cloudy pool water are the pH and the
Calcium Hardness.
2. If the pool chemical levels are not within the following suggested ranges, adjust the
chemicals and run the pool filter system for 12-24 hours before re-testing. Free Chlorine:
1-3 ppm, pH: 7.2 – 7.6, Alkalinity: 90 – 120 ppm and Calcium Hardness: 200 – 350
3. If all the pool chemical levels test in range, the cloudy pool water is caused by fine debris
suspended in the pool water. You should backwash or clean your pool filter following the
manufacturer’s instructions, and run the pool filter system continuously for 24 to 48
4. If the water conditions have not significantly improved you should add a clarifier pool
chemical to the pool water to help your pool filter remove the fine debris from the water.
Continue filtering for 12 to 24 hours.
5. If the water conditions have not significantly improved you should add a second dose of
clarifier, or a stronger clarifier chemical and continue to run your filtration system.
6. Sometimes a pool can be too cloudy for a clarifier. If this is the case you will have to move
up to a flocculent. This will drop any suspended particles to the floor so you can vacuum it
to waste.


  • It is important that you continuously filter the pool water until the water is clear, and 

    closely monitor your pool filter pressure. Backwash or clean the pool filter as needed, 

    following the pool filter manufacturer’s instructions.