- Pool bowl shape and soil type
- Optimal dimensions and depth of the future pool
- Construction of a concrete pool on non-porous soil
- Construction of a concrete pool on heaving soil
- Pool water treatment
- Pool chemicals and alternative water treatment methods
- In custody
In this article: choosing a pool shape; how to calculate the depth and dimensions of the pool bowl; how to build a pool on non-rocky soils; construction on heaving ground; water treatment systems and types of filters; microbiological purification of pool water.
A private pool … a couple of decades ago this luxury was beyond the reach of most homeowners. Note that a concrete container 2 by 3 meters, in one way or another, finished with ceramic tiles and with water changed every two to three weeks cannot be considered a pool. Today we know that a full-fledged pool is not just a concrete container with water, it must be equipped with a set of necessary equipment, including those from the field of water treatment. We will figure out how the construction of swimming pools is carried out, what equipment they should be equipped with and why.
Pool bowl shape and soil type
Work on the creation of a private pool begins with an analysis of the local soil, finding out how deep the groundwater lies and what is the greatest depth of soil freezing in the cold season. The owners of the future pool will be exceptionally lucky if the soil in the area allocated for an artificial reservoir is sandy, gravelly or rocky, i.e. not prone to swelling due to deep groundwater.
On such non-porous soils, you can do without taking measures to protect the pool bowl from damage that can be inflicted on it when the soil swells as it freezes. In the case of clayey soils, where the groundwater is shallow, you will either have to arrange the pool bowl from elastic and flexible polymer-based film materials, or build additional thermal insulation under the bottom and walls of the concrete pool bowl.
On heaving soils, only a rectangular shape of the pool is permissible – this shape will provide the best resistance of the concrete bowl to soil swelling, and it will be easier to lay the heat-insulating layer.
Non-porous and slightly porous soils allow you to build a pool of complex shapes, both classic rectangular and oval, round, conical or more complex geometry.
Optimal dimensions and depth of the future pool
When designing a home pool for households of different ages, it is necessary to take into account their average height: a 2-year-old child – 500 mm; 5-year-old child – 1,050 mm; child 12 years old – 1 350 mm; adult – 1 750 mm.
Now let’s figure out the optimal depth of an artificial reservoir. The pool for children under 5 years old should not be deeper than 500 mm, for children from 5 to 12 years old – no deeper than 800 mm, swimming (i.e. not jumping!) Pool for adults – 1 440 mm. However, the depth of 1,140 mm for adults will not be enough when they jump into the water even from a meter height – here you need a depth of at least 2,300 mm, otherwise there is a high probability of collision with the bottom of the pool. For reservoirs equipped with a 3-4 meter jumping tower, the minimum depth in the perimeter of the jumper’s entry into the water will be at least 3,150 mm – it must be maintained in the 5-meter jumping zone of the pool, then the depth is reduced to the optimal 1,440 mm.
Why shouldn’t you create a pool of one, deep enough depth? The answer is simple – it is unprofitable both at the stage of its creation and during operation, in both cases the costs will increase. The optimal solution would be an artificial reservoir, divided into swimming and jumping zones with different depths, designed for both children and adults..
Depending on the purposes of the future use of the pool, it is necessary to calculate the dimensions of the water “mirror” – for example, for a round pool, the optimal diameter will be 4000 mm. If a swimming pool is supposed to be used, it is required to plan a “mirror” of water under the paths: for one path – width 2 250 mm, length 5 250 mm; two tracks – width 4000 mm, length 5250 mm. Accordingly, for a long pool, the parameters will be as follows: for two lanes, medium length – 4350 mm wide, 8000 mm long; two tracks, long length – width 4 500 mm, length 12 500 mm. That is, the longer the length of the water “mirror”, the wider the pool paths should be.
When choosing a place for laying a pool, it is necessary to take into account the local wind rose – the best option would be such a layout in which the winds blow along the “mirror” of the pool along its length, in this case leaves falling on it and other volatile pollutants will accumulate from the windward side, in which installation of a drain-overflow pipe will be appropriate. Separately, you should pay attention to the trees surrounding the basin of the pool – willow, broom, horse chestnut and poplar will drag their roots to an artificial reservoir, disrupting the waterproofing and damaging the walls of the pool (underestimating the capabilities of these trees would be a big mistake). Ideally, the relief in the area where the pool is supposed to be created should have a natural slope, which will greatly facilitate excavation work and the organization of the water drainage system.
Construction of a concrete pool on non-porous soil
It will be easier and more convenient to build a pool of concrete, which allows you to build almost any configuration of the bowl – you just need to correctly set the formwork, not forgetting that the most convenient shape will be a rectangle, the length of which is two to three times the width.
Having chosen a place taking into account the wind rose and the natural slope of the relief, we mark the perimeter of the pool bowl, we determine the location of the pit for drainage. The dimensions of the excavated pit should be larger than that of the future pool bowl – width and length by 500 mm, depth by 400 mm. When forming the bottom of the pit, it is required to create a slope of 5-7o towards the drainage pit, at the lowest point on the bottom of the pit, a drain pipe with a diameter of 100 mm is installed (before the start of concreting the bottom of the pool). A pipe is laid from the branch pipe to the drainage pit or sewer well under a slope.
A drainage pit is created at a distance of at least 5,000 mm from the near wall of the pool, if there is a natural slope of the relief – down the slope. To create it, it is necessary to dig a hole with the dimensions of 1000 by 1000 mm and such a depth that the bottom of the drainage well is 500 mm below the level of the drain hole on the bottom of the pool (minimum depth – 1500 mm). A drain pipe is inserted into the drainage pit, the bottom of the pit is filled with rubble along the lower part of the outlet of the drain pipe (the minimum thickness of the rubble cushion is 200 mm). A metal casing is installed over the neck of the drain pipe – a box without a bottom, on one side of it there is a recess along the diameter of the drain pipe, then the drain well is completely filled up with large fragments of brick battle, concrete or cobblestone. A metal or wooden cover is laid on top of the finished drainage pit.
Having finished work with the drainage system, we proceed to work on the bottom of the pool. First of all, a sand layer of 50 mm thickness is poured onto the entire surface of the bottom of the pit, and it is carefully rammed using a wooden block with handles for lifting and lowering. Next, a layer of crushed stone cushion is formed with a layer of 100 mm, only a small fraction of crushed stone is suitable here. Having covered the entire surface of the bottom of the pit with gravel, we carefully go through it with a wooden tamper. Next, concrete is laid on the bottom with a layer of 100 mm, after its hardening – a reinforcing mesh of wire and another layer of concrete, also 100 mm.
The casting of the concrete walls of the pool bowl is performed at the stage of concreting the bottom. It should be noted that the formation of a small slope of 5-7o near the walls at the stage of excavation of the pit will facilitate their concreting, because the soil will crumble less, thereby increasing their strength. The panel formwork of the walls is exhibited following the laying of concrete on the bottom along the wall, reinforcement mesh is laid in it and concrete is poured, the binder (cement) grade of which is M500. As the concrete is poured into the wall formwork, it is required to bayonet it – repeatedly pierce it with a piece of reinforcement of sufficient length so that the concrete at the bottom of the pool bowl and on the walls merges, i.e. no seam was formed between them. Further concreting of the walls should be carried out without a long break between pouring, bayonetting and compacting the concrete using a rammer. The thickness of the concrete layer at the bottom and on the walls of the pool bowl must be the same, from 200 to 250 mm.
The screed of the bottom and plastering of the walls is carried out 10-12 days after the walls are concreted – during this period the concrete will gain the necessary strength. To perform waterproofing, you will need a special composition of the screed solution – an aqueous solution of ceresite emulsion is introduced into a dry mixture of cement and sand (ratio 1: 3) (the ratio of emulsion and water is 1:10, called ceresite milk).
Ceresite emulsion is a white or slightly yellowish substance, similar in consistency to sour cream, has an ammonia smell. It consists of ocher, lime, oleic acid and alumina sulfate dissolved in water.
The thick composition obtained from a mixture of ceresite milk and a cement-sand mixture is placed on the concrete surface of the pool bottom pre-moistened with water by rubbing, which will increase the adhesion between the waterproofing layer and the concrete. Then a layer of waterproofing, the thickness of which should not be more than 25 mm, is equal to a trowel, at the final stage it is trowelled. If during the work on concreting and screed it is hot, sunny weather, then it is necessary to cover the surfaces to be concreted with wet burlap, from time to time wetting the concrete with water and not letting it lose moisture until it gains strength.
It is better to finish the pool bowl with tiled materials and glue on special cement adhesives for pools – the combination of these materials will increase the waterproofing of the pool. It is necessary to prepare in advance the plaster, previously applied to the concrete walls, for subsequent tiling. To do this, draw shallow diagonal grooves on the wet plaster with a piece of reinforcing wire – they will increase the adhesion of the tile to the plaster, and you can start gluing the tile after the surface of the plaster dries a little.
Construction of a concrete pool on heaving soil
In Russia, the most common clayey soils are heaving – it is more difficult to build a pool on them than on non-heaving sandy, rocky or gravelly soils, but it is also possible. The owner of a pool built on clay soils should take into account that it is extremely difficult to completely protect the pool bowl from the soil with a high water content swelling in the cold season and the periodic rising to the surface of the groundwater is extremely difficult – it will be difficult to avoid cracking. Below are a number of measures that must be taken when building a pool on heaving soils – they will protect the pool capacity from direct contact with moving soil.
Especially a lot of work will be done with the preparation of the base for the concrete bottom of the pool. At the bottom of the prepared foundation pit, with the first layer of 200 mm, dense oily clay is laid, on top – a 300 mm layer of expanded clay of the middle fraction. To level the surface of the expanded clay layer, a 20 mm layer of sand is poured onto it, after tamping, foam polystyrene plates of 40 mm thickness are laid on it, then another layer of sand, 50 mm thick and, finally, fine crushed stone, 100 mm layer. It may seem to you that such a base for the pool bowl is very complicated, but only such a “sandwich” can effectively perform the role of a damper on heaving soils in cold seasons..
Concreting of the bottom and walls of the pool is carried out similarly to the technology of building a pool on non-porous soils. Upon completion of the casting of the walls, from the outside they must be coated with heated bitumen and with its help, the entire area of the outside of the pool walls with reinforced pvc film must be pasted over (the average price is 30 rubles per m2). A layer of film will prevent the adhesion of concrete walls with the ground when it swells in the winter season, as a result, the soil will slide along the walls and will not damage them. Having glued the pvc film, we proceed to the formation of a castle of oily clay between the concrete wall of the pool and the pit – the walls of the pit should have a slope so that in the lower part the distance between the concrete wall and the pit is 250 mm, and in the upper part it was already 350 mm … An interlayer of dense greasy clay blocks the saturation of the soil with water near the walls of the pool, thereby reducing the scale of soil swelling in these areas, and will reduce the pressure of groundwater on the pool bowl.
In the winter season, additional protection of the pool bottom from freezing is required – if a snowy winter succeeds, then snow will be suitable for the role of a natural insulation, i.e. it should be collected and filled in the pool bowl. If the winter is snowless, it is necessary to lay the first layer of foam or expanded polystyrene slabs on the bottom, cover them with a layer of expanded clay on top.
Pool water treatment
Today, equipment for pools of various sizes and purposes is available on the market in a wide range. According to its purpose, it can be divided into the necessary, to which the water treatment system belongs, and additional, designed to increase the level of comfort of bathers..
When thinking about creating a private pool on their site, most homeowners do not take into account the installation of a water treatment system, suggesting that they solve the problem of treating contaminated water with a simple replacement – pour out the contents of the pool and fill with fresh water, cleaning the bowl of the artificial reservoir a little before refilling. The first two or three times this method looks quite working, but later, against the background of growing water costs and insufficient cleanliness of the pool bowl, its owner begins to search for suitable water purification equipment.
There are two existing systems for intake and filtration of pool water – overflow and skimmer. In pools with an overflow cleaning system, water is constantly located at the upper boundary of the walls of the pool bowl, and along its perimeter there is a horizontal tray covered with a plastic grate. Water from the surface of the pool goes into the trays by gravity and is forcibly pumped out by a pump from the bottom through the drain hole, from there sequentially into the collection tank, into the filter unit, water heater and chemical water treatment plant, where the calculated portion of reagents is added to the water.
The return supply of treated water to the pool is carried out through the bottom nozzles. The advantages of an overflow water treatment system: purification of a significant volume of water in a short time; allows use of the pool depth of 100%. Disadvantages: high cost compared to a set of equipment for skimmer filtration.
In a skimmer water filtration system, water intake is carried out through special overflow skimmers located at the waterline level on one side of the pool bowl. From there the water is piped to the filtration unit, and the water pressure at the inlet is increased by a pump. After passing through the filter, water heater and chemical purification, the water returns back to the pool, entering it through wall nozzles located parallel to the skimmers on the opposite side of the pool bowl. Advantages: a skimmer water purification system is cheaper, there are monoblock skimmers that do not require installation in the pool body (very convenient if the filtration system was not taken into account at the stage of pool construction). Disadvantages: less, in comparison with the overflow filtration system, the volume of purified water per unit of time, the distance from the edge of the sides of the pool to the waterline should be at least 100 mm.
There are three types of filters built into the pool water purification systems – sand, cartridge and diatomite. The filling and the main filtering element of sand filters is quartz sand, they are the cheapest and, in comparison with filters of other types, are large in size. Cartridge filters contain polypropylene membranes in their body, they are superior to sand filters in filtration quality, and, moreover, they have much smaller dimensions and weight. Diatomaceous earth filters are filled with crushed, fossilized marine organisms such as microscopic algae and small shellfish – such filters have long been used in aquariums. They have many tiny pores, so they are most effective in pool water treatment. Any of the described types of filters can be flushed out of accumulated dirt by directing a stream of water in the opposite direction, i.e. to output from the filter. The degree of filter contamination is determined by the readings of a pressure gauge built into the six-way valve at the head of the filtration unit.
Overflow filtration systems and sand filters are used in cleaning systems for large pools designed for dozens of people bathing at the same time. For a private pool, a skimmer water treatment system and cartridge or diatomite filters are quite suitable.
Pool chemicals and alternative water treatment methods
The filtration systems described above can only deal with mechanical pollutants, but additional water treatment is required to completely purify the water and maintain its chemical composition at an acceptable level for bathers. By the way, devices for its implementation are built into the overflow and skimmer treatment systems..
The most commonly used chemicals for disinfecting water in swimming pools are: chlorine stabilized against UV exposure in the form of tablets (90% active chlorine), granules (60% chlorine) or in liquid form (up to 12% chlorine); pH neutralizers, alkali is used to increase the pH level, acid to lower it; algicide, prevents the growth of algae; flocculant (coagulant) for collecting the smallest suspensions in water, sold in liquid form or in the form of tablets.
Disinfection of water in the pool is carried out only with stabilized chlorine, because cheaper unstabilized chlorine is rapidly eroded and destroyed by the ultraviolet rays of the sun. To periodically check the water for pH level, a special tester is required – a pH level in the range of 7.2-7.4 is considered normal. The collection of contaminants grouped by the flocculant is carried out either through the water intakes of the overflow and skimmer cleaning systems, or with the help of a specially water vacuum cleaner with a built-in filter. Chemicals in the form of granules and tablets are manually placed into the pool, the dosage is determined by the volume of water, liquid chemicals are intended for dosed automatic injection through filtration systems or through independent dispensers, usually of a float type.
In addition to chemical reagents, water can be purified by more gentle methods – ozonation, ultraviolet radiation, ionization and using active oxygen.
Water treatment based on the ozonation method is based on ozone, thanks to its oxidizing ability, all microorganisms that have penetrated the pool waters are easily and quickly destroyed. The ozonizer is built into the water filtration system, the ozone generated by it, after the destruction of bacteria, is converted into oxygen, i.e. does not harm a person in any way.
Ultraviolet rays emitted by emitters placed above the pool mirror are capable of destroying all types of microorganisms in a matter of minutes without changing the chemical structure of the water. Special professionalism is required when installing UV emitters, in no case should you be in the pool during their operation – this is dangerous for the skin.
Ionization allows not only to destroy most of the microorganisms in the pool, but also to coagulate the mud microparticles. The meaning of such water treatment is to saturate the entire volume of water with copper or silver ions. The ionizer is built into the water filtration system or placed separately, in a semi-submerged position on the side of the pool.
The method of water treatment with active oxygen is as follows – special chemical reagents are placed in the water, reacting with oxygen. Applied immediately before visiting the pool, treatment with active oxygen provides microbiological safety to the swimmer for several hours. This method is used most often in private reservoirs, cheaper chlorination is used in public pools.
Among the existing types of additional equipment for pools, it is worth highlighting a ladder, floating cover or blinds: if the depth of the reservoir exceeds 1,500 mm, then the ladder will greatly facilitate entry and exit into the water; the plane of the cover or blinds will protect the pool mirror from volatile debris and dust, significantly reducing the amount of work for cleaning equipment.
Interesting additional options will be: pool counterflow, which creates a strong countercurrent for the swimmer and increases the effectiveness of training; hydro and air massage, allowing you to create the effect of a jacuzzi in the pool; waterfalls and geysers. At night, the illumination with multi-colored underwater spotlights will turn the pool into a fairy tale, and the bathing itself will be unusually enchanting!