Pool water treatment

Basic principles of pool water treatment

The pool water is exposed day after day to extremely variable conditions. Every user of the pool, mother nature and the external environment, inevitably introduce organic and inorganic substances into the water.

If you ignore this, the water in your pool will soon become cloudy and unpleasant as failure to treat the water provides the ideal conditions for the growth and proliferation of algae and bacteria in it.

Water treatment is essential, otherwise:

Bacteria will form in the tank which will make the water cloudy and the walls slippery.
The water will soon turn green if the formation of algae is not prevented.
The pool walls will become rough if nothing is done to counteract the precipitation of calcium.
The pH value of the pool water will soon exceed acceptable limits if it is not corrected periodically.
A series of measurements of physical and chemical parameters will help you make sure that the water in your pool remains clean and crystalline, perfectly hygienic and free from unpleasant odors.

Operation of the swimming pool

The circulation of water in the pool, filtration (physical treatment) and the addition of chemical treatment products (chemical water treatment) form the basis of the pool water treatment routine. The chemical and physical treatment procedures are complementary to each other and have the same importance for a truly effective periodic treatment. The circulation and filtration of water alone are not sufficient to keep the water clean and free from micro-organisms. The chemical treatment of water is therefore essential. In this way, bacteria, fungi and viruses can be eliminated just as algae can only be avoided by preventing their formation through the adequate dosage of algaecide products. Furthermore, many particularly fine particles and turbid substances can be removed from the water only by flocculation.

Each pool owner must therefore perform the chemical treatment of the water in the pool in order to be able to bathe in hygienically pure water. Therefore, knowledge of the basic principles of pool water treatment is crucial for a truly effective and economical treatment. On average, pool treatment procedures take no more than 10 minutes per week and will soon become a routine practice.

Calculation of the pool water volume

First of all you need to know how many cubic meters of water your pool contains in order to make the correct dosage of disinfectant products. The formulas used to calculate the volume of water will vary depending on the shape of the tank:

Rectangular pools:
length (in meters) x width (in meters) x depth * (in meters) = …… Mc

Oval pools:
maximum length x maximum width for depth * x 0.89 = …… Mc

Double circle or 8-circle pools:
max length x max width for depth * x 0.85 = …… Mc

Round pools:
diameter x diameter x depth * x 0.79 = …… Mc

* Depth = average depth of the pool water.

Physical water treatment

Most of the larger polluting particles are retained by the filter in a well-built system. We generally suggest running the filtration system in order to allow the filtration of all the pool water 2–3 times in a day. Normally this corresponds to filtration times of approximately 6–8 hours. If you use a sand filter you will have to backwash the filter at least once a week, taking care to restore the water level in the pool by adding fresh water. The procedure indicated for sand filters can also be followed for other types of filters. In any case, it is recommended to carry out backwashes that lead to a subsequent refilling of water in the pool equal to at least 3% of the total volume.

Large particulate pollutants that end up in the tank can be removed using the screen or an automatic cleaner.

Chemical water treatment

The chemical treatment of water includes 4 different phases:
1. The regulation of the pH value
2. Disinfection
3. Prevention of algae
4. The flocculation
Each pool owner can choose between 3 different treatment methods:
– The method of disinfection based on active oxygen
– The chlorine-based disinfection method
– The bromine-based disinfection method

The regulation of the pH value

Adjusting the pH value is essential for proper water treatment. The pH value of the water indicates its tendency to be acidic or alkaline. The pH value is also an important parameter for obtaining an effective disinfection treatment. The ideal pH value for an excellent water treatment is in the range between 7.0 and 7.4. The pH value can, however,

vary considerably depending on the hardness and temperature of the water and must therefore be measured regularly and at least once a week. The measurement is traditionally performed with the Pool-Tester. Dissolve the phenol red (DPD pH) tablet in the measuring cuvette without touching it with your fingers and compare the color obtained with the color scale shown on the tester. Measuring pH is therefore child’s play using this tool.
A pH value outside the indicated range could cause the following problems in the case of water that is too acidic or alkaline:
acidic water (ph between 0 and 6.9) involves:

Corrosion of metals
Aggressive water on metal-containing fittings
Deterioration of flocculation

alkaline water (ph between 7.5 and 14.0) involves:

Irritation of eyes and skin
Decrease in the effectiveness of disinfection products
Deterioration of flocculation
Tendency to calcium precipitation
Periodic adjustment of the pH value will reduce the need for treatment products as the effectiveness of disinfectants is greatly reduced by a high pH.

If the pH value is too high (over 7.4), the pH-Minus product must be added to the water. The pH value will gradually drop after adding this product.
If, on the other hand, the pH value is too low, then the product to be added will be the pH-Plus which will increase the pH parameter in the water.

Disinfection of water

Pool water is an excellent living environment for various microorganisms (bacteria, fungi, algae). Only a small part of bacteria and fungi are pathogenic and pose a risk to the health of bathers, but even microorganisms that are not dangerous to health can create problems in the pool by causing turbidity and slippery deposits on the bottom and walls. Water disinfection is therefore the only effective solution to eliminate these microorganisms and, with them, the problems they cause, while maintaining hygienically pure water.
You can choose between three different water disinfection programs:

chlorine-based disinfection
disinfection based on active oxygen
bromine-based disinfection
a) Disinfection of water with chlorine
Traditional disinfection with chlorine not only has bactericidal effects, but also eliminates impurities and non-filterable organic substances, through oxidation (the so-called cold combustion). Disinfection with chlorine is the most reliable option, especially when the water is subject to strong contamination, for example due to temperatures constantly above 28 ° C or due to particularly difficult environmental conditions that bring many pollutants in Basin. With the development of various stabilized chlorine-based products, chlorine-based treatment has become simple and safe.

b) Disinfection of water with active oxygen
Consumer demand for more delicate, chlorine-free products has led to the development of new treatment programs, in particular based on active oxygen. The active oxygen-based treatment system offers numerous advantages:

– No chlorine smell
– Particularly gentle on the skin
– No type of redness or irritation to eyes or mucous membranes.
– The water is considerably more pleasant and resembles fresh spring water
– After the bath the skin and hair are not dry.
– It is completely non-foaming, with neutral pH and does not contain heavy metals, so there is no risk of metal precipitation.
It is also compatible with chlorine so you can possibly switch to the chlorine-based method or make chlorine shocks at any time you deem it necessary.
– Guarantees safe and effective disinfection.
– It also has an effective algaecide action that prevents the formation of algae.

c) Bromine-based water treatment
Bromine-based disinfection is an effective alternative to the use of chlorine. Bromine, like chlorine, is a halogen and this makes it particularly suitable for the treatment of swimming pool water. Bromine is very efficient in fighting bacteria, viruses, fungi and eliminates organic water contamination by means of the oxidation process.
Bromine has the following benefits:
– Bromine does not have the unpleasant smell of chlorine
– Does not irritate eyes or skin
– It is free of calcium, has a neutral pH and can be used regardless of the hardness of the water.
– It offers excellent savings in the disinfection phase thanks to its high tolerance to changes in the pH of the water. 87% of the disinfectant power is also maintained at the very high pH value of 8.0, unlike chlorine which at the same pH has only 33% disinfectant capacity.

This treatment method is particularly suitable in the case of swimming pools where the smell of chlorine is annoying but where a strong disinfection and safety capacity is still required as for

the whirlpools or spas. From the user’s point of view, bromine arises as a middle product between chlorine and active oxygen.

Prevention of algae formation

Algae are the oldest life form on earth. Among the 10,000 existing types of algae, there are unfortunately some specimens that prefer the pool as an environment for their proliferation. Algae are plant microorganisms that produce unwanted organic substances. These substances in turn constitute the ideal food for bacteria and fungi. The algae reproduce and spread through spores that are carried everywhere by the dust present in the air. They can therefore reach any swimming pool, even those closed inside homes. It is therefore necessary to prevent its growth.

Disinfectant products by themselves are not always sufficient to avoid algae growth. Some types of algae may also be resistant to chlorine, since the disinfectant molecule does not always pass through the mucous membrane that covers the larger algae colonies.

The Flocculation

The pool water is filtered to eliminate dirt and turbidity. However, the filter is able to retain only the larger dirt particles. Smaller particles can only be retained by means of additional measures. Flocculation allows you to remove even the smallest particles. The flocculant is added before the filter and forms flakes in the water, capable of retaining even the finest polluting particles, trapping them on their surface so that there is a larger element that can be blocked by the sand contained in the filter. The elimination of this dirt and of the flocculant itself occurs through the normal filter backwashing operation.
In addition, good flocculation contributes to increasing the effectiveness of the disinfectants used. The quality of the water is significantly improved by using the flocculant and you can enjoy swimming in your pool in crystal clear water. Flocculation is suitable for any type of treatment and its effect is particularly evident in the case of treatment based on active oxygen. Result: the filtered water is crystal clear and impeccably clean.

Automatic water treatment

DOSITA SRL offers various advanced equipment for automatic analysis, control and dosage operations that guarantee constant hygiene and impeccable water quality.
They are the ideal tool for anyone who does not want to use manual treatment products.

The advantages of automatic water treatment are as follows:
– Automatic dosing of disinfectants and pH regulators: for a more effective and economical water treatment than products to be dosed manually.
– Safe disinfection even during periods of high bathing frequency and with high concentration of pollutants.
– There is no need for shock treatments even when the pool is not used for long periods, saving chemicals.
– The simple, proven and effective technology minimizes the need for maintenance.
– The type of dosing pumps used guarantees minimum noise during the operation of the equipment
– Audible and visual alarms immediately report unexpected parameter changes
set or detected.
– The system is easy to install

Periodic water analysis

The chemical treatment of swimming pool water is based on the correction of two fundamental parameters: the pH value and the disinfectant content. For this it is essential that an analysis of these variables is carried out at least once a week.
Regardless of the treatment system you have decided to adopt, whether with chlorine or oxygen, the analysis of water parameters is very simple and fast with the DOSITA analysis tools.

The ideal pH value is in the range of 7.0-7.4, the disinfectant concentration level depends on the treatment program adopted.

Additional indications

a) Start of season
If the pool is empty and without calcium deposits or dirt deposits on its surface, check the filter and fill the pool as well. First of all, adjust the pH value between 7.0 and 7.4, then program the type of water treatment you will perform and possibly perform a chlorine shock. After the chlorine shock, let three days pass before starting the actual water treatment.
Remember that once the tank has been filled, the pH tends to vary very quickly in the first few days and must consequently be measured and adjusted more

b) Cleaning
Cleaning the tank is an essential prerogative to subsequently have hygienically pure and crystalline water. It is advisable to clean the pool, empty, at least once a year. This rule applies not only to outdoor swimming pools but also to indoor pools or inside homes. This is because calcium precipitations, grease and dirt deposits are a common presence in all tanks, even in those with apparently clean water. Cleaning with empty tub removes both visible dirt
that the microorganisms (invisible bacteria) that lurk on the surface of the tank.

The cleaning of the tank should be carried out regularly even when the tank has been filled as grease, dust, oils and creams brought into the water by bathers are deposited in a particular way on the edge of the tank.
We should be very careful to use non-specific detergents for swimming pools and perhaps of low cost and quality: these introduce substances into the water that could cloud it and generate foam as well as favor the development of algae. Furthermore, many non-specific products can damage the pool by ruining its coating, in particular that of pools coated with PVC (liner).

c) Stabilization of hardness
The hardness of the water can be divided into total hardness and carbonate hardness and is expressed in ° dH (German degrees)

Light Water
In this case the pH value is not very stable.

Hard water
The greater the hardness of the water, the greater the risk of calcium precipitation and trobidity of the water.

In regions with a high value of water hardness it is greater the probability that the walls of the swimming pools become rough, that the filters become clogged and the heat exchangers become encrusted or clogged, considerably reducing their heating performance, thus increasing energy consumption (an encrustation 1 mm into the exchanger reduces heat transfer by 15%).

d) Additional dosing tools Disinfectants in concentrated form (such as chlorine tablets) should not be dosed directly in water and placed in contact with painted or synthetic surfaces (such as liners) as there is a risk that they may whiten the surfaces same. You have to dissolve them in water using the floating dispenser.

Follow the basic rule for using the products:

Always melt the tablets using the floating dispenser.
It would be easier to recommend the dosage in the skimmer for each type of tablet, but it is not recommended since much of the disinfectant effect would be lost during the passage of the solution through the filter. The best dosage is therefore that carried out by means of the floating dispenser.

e) Avoid whitening of the tub surface. Concentrated treatment products have a whitening effect. For this reason, slow-dissolving tablets should never be thrown directly into the pool but placed inside a floating dispenser or in the skimmer. Fast solubility tablets dissolve best in the skimmer with the circulation pump running.
On the other hand, there are no risks of whitening the surfaces using the granular products that can be dosed directly in water as they dissolve immediately. For greater safety, also in this case, run the circulation pump and dose the granular product along the perimeter of the tank, preferably near the outlets.
Attention: if chlorine comes into contact with clothing there is a risk that they will be discolored, if not immediately, during the next wash.

f) Holiday treatment

Anyone who does not have automatic control and dosage equipment and must be absent for more than 8 days must take care to ensure adequate treatment in the period of his absence.
It would also be advisable to cover the pool if it is not being used. In any case, the circulation pump should not be turned off, to ensure adequate filtration, if anything, its operation should be reduced (to half the normal working time). If you have a sand filter, perform the following procedures: backwash with a replacement of an adequate amount of water, adjust the pH value between 7.0-7.4

If you have a cartridge filter: carefully clean the filter, adjust the pH value between 7.0-7.4 and fill the floating dispenser with an adequate number of tablets (the number of tablets to be put into the dispenser will vary according to the size of the pool). By reducing the opening of the slots of the floating dispenser, you can obtain sufficient treatment for about 3 weeks. Don’t forget to dose the product twice as normal to prevent the formation of algae.
On your return, even if the water is clean, first of all do not forget to backwash the sand filter or clean the cartridge filter.

g) Care of the filter
As a rule, the filters should be cleaned by backwashing at least once a week in order to remove the dirt that has accumulated inside them. In case of hard water, despite regular backwashing, calcium deposits may form inside the filter which in the long run could clog it reducing the filtering capacity.

We therefore recommend descaling and cleaning the filter 3-4 times a year.

Pool filters are an ideal environment for the proliferation of bacteria and the accumulation of dirt. Normally the filter should be completely clean after backwashing. Cloudy water, high consumption of disinfectants and a strong smell of chlorine, however, are clear indications that there is something wrong with the filter. Proper disinfection and the removal of turbidity through flocculation are essential procedures to ensure excellent filter functionality. However, the sand contained in the filters should be completely replaced every 2–3 years.

h) Care during the winter months

Almost all manufacturers and builders of swimming pools recommend leaving their pools, installed outdoors, full during the winter by only lowering the water level below the vents. There are many advantages of this procedure: if objects were to fall into the pool, the water would attenuate the impact that could otherwise damage the pool. Furthermore, keeping the pool full prevents any movements of the ground or pressures due to the raising of the water tables from damaging it. Furthermore, a swimming pool kept full is less affected by climatic variations.

A further advantage is obtained from the dosage of a specific product for the wintering of the pool. This product in liquid form prevents calcium precipitation and algae formation, thus making spring cleaning easier when the pool is reopened.

Keep in mind the following points for wintering the pool:

1. Adjust the pH 7.0 and 7.4.
2. Make a chlorine bump (to always be performed with the circulation pump running) so that any impurities cannot “hibernate” during the winter and then become active again when reopening.
3. Once the pool is no longer used, lower the water level under the skimmer and the vents to protect the circulation accessories from any ice formation on the surface.
4. Add the appropriate amount of product to the pool.
5. Empty the pipes of the circulation system and put the filter valve on “closed”.
6. Insert any dilating vessel object in the tub that can compensate for the pressure of the ice.
i) Fresh water replenishments / Backwashes / Total water changes
Even if the pool is regularly and perfectly treated, over time the accumulation of substances dissolved in water (especially salts formed by the reaction of chlorine such as chlorides and nitrates) cannot be excluded. High concentrations of chlorides have a corrosive effect on the metal parts of the pool, especially on aluminum and also on the best stainless steel.

An excessive concentration of salts can only be prevented by regularly replacing part of the pool water with fresh water. Pools with very hot water in which there is strong evaporation are more subject to the accumulation of salts and require greater attention to replenish fresh water. In the case of private pools, the quantity
of fresh water to be added every week should be at least 3 or better still 5% of the total volume of water contained in the pool. These quantities are equivalent to about a 5-minute backwash (if obviously the filter is adequately sized).
The cover sheets significantly reduce the amount of evaporated water and therefore also reduce the necessary amount of fresh water to be added. Even in well-treated swimming pools, the accumulation of salts that cannot be removed by means of the filter or chemicals cannot be avoided. The only way to solve this problem is to change the water. Therefore, the general rule would be to completely change the water at least once a year for outdoor pools and every 2 or 3 years for indoor pools, even if the water is apparently clean. In the case of outdoor pools, it is preferable to carry out this operation in spring, thus taking advantage of the emptying of the pool also to clean the surface of the pool.
j) Filling water / metal precipitation
Pools with cartridge filters should only be filled with mains water. If, on the other hand, your pool has a sand filter then you can also choose to fill the pool with well water, taking care to follow the instructions below. If the filling water contains iron, manganese or copper (usually present in private wells) it is very likely that it takes on an unpleasant color (between rotten green and brown until it almost becomes black) and moreover that it is very cloudy.
This is due to the precipitation of metals but this does not necessarily mean having to empty the pool since it is possible in most cases to make the water clean through flocculation. Proceed as follows for the best removal of unwanted metal ions:

1. Bump chlorine to oxidize all the iron and manganese
2. Adjust the pH carefully
3. Flocculate to remove iron and manganese by letting the filtration system work continuously for a few days.

The pH that tends to increase should be checked and adjusted with particular attention during the first days after filling. The initial dosage of the products must also be checked and calibrated according to real needs as it can vary according to the different level of impurities present in the filling water.
If there is iron in the water, it will quickly take on a green to brown color.
If your pool is not equipped with a sand filter, then you should not use this well water.

k) Special features of whirlpools, spas and small pools.
If you own a SPA or whirlpool, you will have to follow special precautions: In the whirlpool there is a continuous flow of water and bubbles are generated by the injection
of air in water. Furthermore, the water temperature is generally higher than that of a normal swimming pool. Whirlpools are therefore more prone to the accumulation of particular types of bacteria that proliferate very quickly in a warm environment and increase the risk of infection.

The correct use of chemicals

Always remember that chemicals are highly concentrated and designed for the treatment of swimming pool water and certain safety measures must always be taken for their use. These products should always be used only for the purposes indicated. Read the instructions on the labels carefully before using them. Some basic indications are as follows:
Instructions for storage and use:
– Always keep chemicals locked up and store them in a cool, dry and well ventilated place. Avoid direct exposure of the products to the sun.
– Do not store chemical products in the same environment where you keep food, corrosive and flammable substances such as solvents and thinners, oils, paints.
– Do not mix chemicals with each other. Do not mix different types of chlorine with each other or with other chemicals whether they are in liquid or solid form.
– Avoid contact with eyes and skin. Solid chemical products that should be spilled should be sucked up and in the case of small quantities washed off with plenty of water. If the payment of the product should be of large quantities, consult your dealer.
– If the products come into contact with the eyes, rinse them immediately with plenty of water and consult a doctor. Don’t forget to show the doctor the jar of the product with his label.
– Remove the concentrated product from skin, clothes and non-acid-resistant materials as soon as possible, rinsing them with plenty of water.
– Keep all chemicals out of the reach of children, unauthorized persons and animals.
The various hazard symbols, included in the orange squares, are affixed to each package that requires their application. These symbols vary from one product to another and are used throughout Europe to indicate the potential risk associated with the concentrated chemical product in question.