Elimination of algae in swimming pools
The management of swimming pools, both for sports and leisure use, requires knowledge of a number of factors, of a physical, chemical and biochemical nature, without which it can be difficult to keep the water in which you swim clear.
One of the most frequent problems is that of algae.
The algae enter the water in different ways, for example they are introduced by microscopic particles on someone’s swimwear, or by a small speck on the equipment, inflatables or toys that are inside your pool. But wind and humidity are also some of the causes that cause algae to bloom in the pool.
Unlike toxic algae, such as ostreopsis ovata, which can form in marine waters, none of the three types of algae that can proliferate in the pool are dangerous for humans.
However, the algae in your pool can make the water so cloudy that you won’t be able to see a person in trouble while diving. Add to this the fact that the algae in the pool provide food for some types of bacteria that can create some problems.
When the water in the pool starts to get cloudy, this is a sign that algae are starting to proliferate.
Depending on the type of algae that infects the pool, the color of the water can become greenish, yellowish or even blue-black.
Another sign is the presence of some sort of residue of one of these colors on the stairs, in the corners, on the walls of the pool and around the jets and skimmers.
Types of algae –
In order to establish the type of algae, it is necessary to look closely at all the points where the algae begin to grow and to understand how to eradicate them we begin to classify them:
– green alga; it is an alga whose color is given by chlorophyll. It is the most common problem in the pool and also easier to eradicate. Green algae float in the water, making it cloudy and giving it a greenish tinge. They also stick to the walls and floor at the bottom of the pool. Poor filtration and the lack of adequate sanitation favor the growth of green algae. It can be brought into the pool by swimwear and toys that have been used in natural waters;
– yellow seaweed; it can be mistaken for pollen or sand in a shady corner of your pool; it is almost certainly yellow alga instead; yellow algae are also called brown or mustard algae. Although it is a rarer seaweed and is not slimy, it is resistant to chlorine, which makes it difficult to treat.
– Black algae; these, in fact, are represented by a cyanobacterium and not by an alga. It is an organism that reproduces easily and, in addition, its roots can burrow into concrete surfaces, making it difficult to get rid of black algae from your pool. For this reason it grows back quickly if the treatment is not aggressive enough to ensure that none of the roots hang around.
– pink slime; this is also a bacterium that grows in swimming pools, especially inside polyvinyl chloride (PVC) pipes. It is sometimes called pink algae, although this is a misnomer. It is an eliminable presence and is not harmful to humans.
The system for eliminating algae from the pool is the same for all three types of algae mentioned above, with one exception that we will mention below.
Algae Elimination –
The initial method is that of manual suction as pool robots are not designed to eradicate the proliferation of algae.
The most effective method is to manually switch the aspirator to “drain” mode, bypassing the filter to prevent the recirculation of contaminated water. With this operation, particular attention must be paid to the points where algae can easily form, such as ladders, steps, in corners, on walls and around jets and skimmers.
It will also be necessary to brush the walls and the bottom of the pool; this allows to physically eliminate most of the algae and to ensure a more aggressive action of the chlorine against the remaining residues.
During this operation, particular attention must be paid to the corners and shaded areas, where algae usually take root more, especially in the most difficult to reach points and then proceed with those where the cleaning action is simpler.
It is therefore important to evaluate the alkalinity and pH of the water. For a quick analysis, you can use the test strips or a digital kit. In fact, water with low alkalinity inhibits shock chlorination (ie the shock treatment).
In fact, the more resistant types of algae require more aggressive treatment, so if the infection is extensive, you will need a lot of chlorine to drastically reduce their presence.
In this regard, calcium hypochlorite shock is recommended, following the instructions carefully to evaluate the required amount.
Then multiply this amount by 2, 3 or 4 times based on the type of algae that has proliferated in your pool.
In general, the quantities are:
– green alga: multiply x 2,
– yellow or dark green algae: multiply x 3,
– black algae: multiply x 4.
Furthermore, the advice is not to use stabilized chlorine as you will end up having an excess of cyanuric acid, which inhibits the disinfectant, and can lead to the proliferation of algae in your pool, or to have worse problems. It is also advisable to place the equipment for cleaning the pool in the shallowest part while performing the sanitization, in this way your tools will also be sanitized.
Once the so-called shock or shock treatment has destroyed the algae, the pool water will become cloudy and with a blue tint.
At this point it is necessary to reactivate the filtration system continuously for at least eight hours, or until the water is clear again. To speed things up, you can also use a clarifier (flocculant) specific for swimming pools.
Once this is done, a second pool water test must be performed.
This second test is very important, as you need to know that the pool water chemistry is balanced and that the chlorine level has returned to normal.
At this point, to avoid, after so much effort, that the algae return, it is necessary to clean the filters of the pool (which could be full of microscopic particles of algae) by immersing them in diluted muriatic acid, or a simpler and more effective solution, replacing them.
As usual, we recommend the use of the clarifier, which helps to effect a flocculation that makes it easier to remove algae in the pool
In general, when you notice the presence of algae in the pool and have not yet started an uncontrolled proliferation, you can use a clarifier to eradicate them and save much of the subsequent work. The clarifier works by binding to floating algae particles, flocculating them and making suction easier.
If you have a multiport valve on your pool filter, turn off the pump and turn on the recirculation. In this way the clarifier will mix without filtering the water, adding a recommended amount.
This operation must be performed by circulating the water for a couple of hours, then the pump is turned off and left to rest for the whole night. As mentioned, the clarifier will bind to the algae, then it will settle on the bottom of the pool.
However, turn the multiport valve to Waste mode so that the dirty water does not return to the pool.
Hook the hose for the backwash to the door for the backwash / waste and direct the waste water appropriately.
Swimming pool suction –
This is done to ensure that all sediment is removed from the bottom. If the water becomes too cloudy, you need to stop and let the particles settle again before continuing with the suction. During this operation it is good to add water while vacuuming to remove much more material from the bottom.
After aspiration, a double shock treatment must be done to eliminate residual algae. It is best to brush the edges and floor of the pool before doing the shock treatment.
Activating the filter –
In general, 30 grams of algaecide are worth 2 hours of work for this operation. It is not used to eliminate algae from the pool, as although this product kills them it is much more effective as a preventive measure than as a corrective measure.
At this point, after having thoroughly cleaned your pool, wait for the chlorine to drop by a value of around five parts per million, after which a dose of algaecide can be added. Now you will have to brush the pool to remove the last bits of seaweed that are not seen. The algaecide will kill them so they can be filtered out.
Using the cover sheet –
Most of the algae or some bacteria proliferate thanks to photosynthetic activity; the use of a cover sheet, at least for smaller pools, is a good remedy when they are not used. In addition, the sheet, for swimming pools located in more dusty areas, guarantees a lower presence of solid substance which, in addition to being a factor of turbidity of the water (and therefore to be filtered), can be a vector of other algae and bacteria spores which considerably complicate the pool cleaning operations.
Final and ordinary management tips –
Proper pool maintenance helps keep algae away. However, some rules and precautions must be followed:
– First you need to make sure that the water chemistry is balanced; for this reason it is necessary to leave the pump on for 8-12 hours a day and perform “shock treatments” with a certain regularity;
– before introducing equipment, inflatables and toys into the pool, they must be thoroughly cleaned with a bleach-based detergent or with a sanitizing solution obtained by adding a spoonful of bleach to every 4 liters of water;
– also swimwear can bring algae into the pool. Obviously it will be impossible to check those of the guests but it is important that those who usually use the pool carry out this operation;
– if you have a concrete swimming pool and it has some cracks (a joint, a tile, etc.). it must be repaired immediately. These engravings are a perfect hiding place for algae, as they are shaded and almost impossible to clean;
– we immediately clarify that salt water pools are not immune to algae and, moreover, the procedure for removing algae in these is exactly the same as for a chlorinated pool. Just remember to use shock calcium hypochlorite.
– even if all these operations are carried out, it is possible to witness, at times, the proliferation, even less so, of algae. In general this occurs when you have high levels of humidity or wind, which are just two examples of factors that cannot be controlled. The important thing is to act as soon as you notice the algae in the pool, because they can grow rapidly and proliferate, becoming more difficult to eliminate with each passing day. Additionally, even a small amount of algae spores after cleansing and shock treatment will cause new algae to bloom. When you notice them, you need to act quickly and aggressively, and also make sure that the application of the algaecide becomes part of the normal water care routine.