How to clean a swimming pool guide

Ned Kampmann

There are four main methods of how to clean a swimming pool: mechanical, biological, chemical, and with the help of ultraviolet radiation.

Mechanical cleaning of the reservoir eliminates mechanical debris. Biological cleaning normalizes the balance of nutrients in the water. Exposure to ultraviolet radiation kills bacteria and unicellular algae. Chemical cleaning normalizes the chemical composition of the water in the reservoir.

This article will explain how to clean your pool and how to get pool water clear.

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Swimming pool water cleaning

The stages of pool pollution

The first stage comprises mechanical blockages by debris – fallen leaves, needles, twigs, the dried stems of plants, pollen, lint, as well as plastic bags and other household waste. All this garbage floats on the surface of the water for several days and then sinks and begins to rot.

How to clean pool leaves

At the second stage the pool can already be considered “dirty”. Its surface is coated with an oily film and it usually gives off an unpleasant smell. Pools with very muddy water smell no better.

The next stage is the loss of species diversity, i.e. the filling of the reservoir with one type of vegetation, which almost completely displaces all the others. Usually outdoor swimming pools are prone to duckweed, cattail (this plant with broad leaves and brown buds-cobs is often wrongly identified as reeds), and blue-green algae (with severe outbreaks of flowering they release toxins dangerous for animals, fish and humans).

How to get pool water clear from oily film

An increase in gas in the reservoir is another sign of contamination. Fortunately, chemical contamination, for example with petroleum products, is not often found in pools. This problem is mostly caused by pools that are replenished by storm water flowing from major roads or ones located in areas with a significant number of industrial enterprises.
Small amounts of gasoline from the lawnmower getting in the water is not so scary – this is quickly “neutralized” by microorganisms present in the pool.

Random ingress of a small amount of gasoline from the lawn mower is not so scary – it is quickly “neutralized” by living in the pool microorganisms.

 How to clear a cloudy pool

The main causes of pollution

There are two main reasons for the contamination of your pool. The first is when harmful organic matter, fungi and bacteria accumulate on the bottom. This significantly decreases the oxygen content in the water. The effects can be different, ranging from the appearance of an oily film on the surface to the growth of duckweed.

The second cause of pollution is the presence in the water of too many nutrients (phosphorus and nitrogen, which are waste products of fish and animals, as well as the result of dead plants decomposing). The levels of such nutrients in the water can be reduced with underwater vegetation such as potamogeton or ceratophyllum.

Swimming pool cleaning DIY

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How to clean a pool with mechanical cleaning

Mechanical swimming pool cleaning is the easiest and cheapest way to get rid of excess aquatic plants, algae and debris. Mechanical filters operate by passing water through a container filled with a porous material (quartz sand, gravel, or special pellets). Organic particles and algae are removed by backfilling and deposited in the filter. The finer the filter material, the smaller the particles it sifts out.

How to get pool water clear DIY

Another tool for mechanical cleaning can be even an ordinary net for catching floating debris. If you don’t want to do it manually, use the skimmer. The filtering part of the structure is a plastic tank with a grate at the bottom. The skimmer is placed directly into a pool. Due to the fact that the upper edge of the basket is just below the surface, the device constantly draws in water and floating debris. The skimmer pump is responsible for discharging the liquid and any dirt is left on the grid.


For mechanical cleaning of the bottom and walls you can use an “underwater vacuum cleaner”. At its core is a conventional vacuum cleaner, but it sucks in dirty water with different suspensions – bottom silt, algae, and the dead remains of plants. The cleaner is usually equipped with some additional accessories that allow algae to be cleaned off rocks or the insides of narrow slits to be vacuumed. When the container becomes filled with sludge, the vacuum cleaner should be turned off. Such a vacuum cleaner can only be used in pools with an artificial frame (concrete, polymeric form, or film). Pebbles on the bottom will not hinder the process if they have a diameter greater than 0.4’’ (10mm).

How to clean a swimming pool DIY

How to clean a cloudy pool with biological treatment

Biological treatment is based on the biochemical decomposition of organic matter (proteins, fats, and carbohydrates) to methane, hydrogen sulphide and carbon dioxide. It is performed by aerobic and anaerobic bacteria in special devices. Biological treatment filters can be found in the product range of almost all firms specializing in this sphere.
In the biological filter chamber is a porous substance in which microorganisms are broken down. This is the main solution to the problem of a cloudy pool.

How to clean a pool with biological treatment

How to get pool water clear the chemical way

Chemical cleaning of pool water is performed by adding different chemical reagents and makes it possible to restore the normal pH of the water to remove harmful ammonia and metal compounds, saturate a pool with oxygen and dissolve algae.

When using chemicals it is recommended to strictly observe all the instructions concerning dosage because certain substances in excessive doses are harmful not only for the flora, but also for humans. The majority of such chemicals are created so that their residues are decomposed into water and carbon dioxide and, therefore, are harmless.

The use of chemicals in many cases can be avoided if your pond is home to not only decorative but also useful plants. For example, the so-called plant-oxygenerators (callítriche, hornwort, fontinalis, and elodea). They contribute to the saturation of water with oxygen.

 How to clean your swimming pool chemical way

How to clean a swimming pool with ultraviolet radiation

One other possible method of water treatment is the application of ultraviolet radiation, which affects the DNA of viruses, bacteria, and microalgae, thus effectively killing them. The UV filter design should be complemented by a mechanism that prevents the growth of algae on the lamp. This may be positioned along the lamp’s plastic rim, on the inner side of the foam and can be set in motion using a special handle on an external filter case. To maintain the intensity of UV radiation it is recommended to replace the lamp every one or two seasons.


Water quality

The level at which your pool will be suitable for plant life and swimming largely depends on the water you fill it with. Depending on its origin, the water in the pool will have different properties. First of all, it can have different levels of hardness and acidity. Water hardness is determined by the content of dissolved salts of calcium and magnesium.

Water that is too hard causes the formation of deposits on the working parts of the pump, fountain and filter equipment, resulting in it breaking down more quickly. Water that is too soft and poor in nutrients slows down the development of plants. Special indicators and test sets are sold in garden centers, which allow you to measure the level of water hardness. The normal level of water hardness in a pool is not higher than 7 mg• EQ/dm3 (200 dn).

How to get pool water clear with chemistry

The acidity is determined by the pH level. A neutral pH is 7. Lower values for water are considered acidic, and higher ones – alkaline. From time to time the level of acidity of water in the pool should be measured, because it may change after precipitation, and also due to exposure to sunlight, which can contribute to the formation of new chemical compounds.

Check out our algae in pool removal guide

Where to get water for pools

To get water for the pool best of pure spring or well if you are sure that they are clean. Springs flowing near highways, often contain oil impurities caught in them along with stormwater.

It is best to source water for your pool from a pure spring or well if you are sure that they are clean. Springs flowing near highways often contain oil impurities along with storm water.
Centralized water supply systems, involving centralized treatment, contain large amounts of chlorine. Therefore it is recommended to pre-fill the tank, wait a few days until the chlorine disperses, and only after that to fill the pool. A good option is rainwater, as it is soft and does not contain lime, nitrates, or phosphates. This means that it is poor in nutrients, and algae will struggle to spread.


Thorough pool cleaning

Pools with flowing water do not need to be cleaned as thoroughly as those with stagnant water. Harmful conditions occur less frequently in conditions of constant water change. The illumination of the pool also impacts on this.

How to clean a pool: complex cleaning

Full cleaning of the basin includes all three essential stages: mechanical, ultraviolet radiation, and biological. The sequence of stages can be changed: first can be applied treatment with ultraviolet radiation, then mechanical cleaning and biological filtration. In the second case, the mechanical filter will pick up a greater amount of garbage, which will have existed in the pool initially and formed after the passage of the water through UV disinfection units (for example, clumps of algae). It is important to understand that buying just one of these filtering methods will not solve the problem of maintaining the purity of pool water. Thus, ultraviolet radiation destroys algae, but does not remove it from the water, which is the task of mechanical cleaning. A biological filter working alone will find it difficult to cope with a heavy load – it will frequently become clogged. That is how to clean your pool thoroughly.

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