Rules for designing swimming pools for public use

The design of a collective sports pool cannot ignore specific national and regional regulations.

The usability and usability of collective sports facilities for swimming and other aquatic disciplines are regulated by international standards dictated by the respective Federations, by national legislation, by the coordination and control activity of CONI, by UNI standards, as well as by the provisions of the Ministry of the Interior regarding safety in the presence of spectators (standards against "violence in stadiums").
To these are added, or should be added, the regional regulations which are responsible for sanctions in the event of non-compliance, but the Italian panorama, even in this segment, is rather fragmented.
However, the standards dictated by UNI with the participation of CONI for sports facilities (in particular UNI 10637) already define a rather detailed framework, much more than in the case of other public facilities which enjoy greater flexibility.

A first idea on the subject, specific for swimming pools, comes from Ministerial Decree of Health 11 July 1991 - Memorandum of Understanding between the State and the Regions on the health and hygiene aspects concerning the construction, maintenance and supervision of swimming pools.
It is certainly not the most recent act (indeed it was suspended in 1993 and then revised by the STATE REGIONS CONFERENCE SESSION OF 16 January 2003 - Agreement between the Minister of Health, the Regions and the Autonomous Provinces of Trento and Bolzano regarding the health and hygiene aspects for the construction, maintenance and supervision of swimming pools), but it is an excellent first starting point to stimulate design sensitivity towards this type of sports facility.

Let's leave aside the open-air pools and focus on the A1 category pools, for public use, covered, mixed-type and convertible-type, that is, those that can operate not only in summer and in which heating and ventilation systems are required.

By plundering paragraph 7 of art. 3 of the 1991 Decree, we refer to the sports facility for swimming rationally connected, with adequate public transport services, to the relevant catchment area and in particular to schools, residential areas and any other sports centres present in the area concerned.

In paragraph 4 of article 2 the types of tanks are defined. Also in the compliance with the current rules of the Italian Swimming Federation (FIN) and the Fédération Internationale de Natation Amateur (FINA), the tanks are divided according to their use and among the most important aspects we point out:

• as regards competitive pools, minimum depth 1,10 m;
• recreational and swimming training pools, suitable for playing, bathing, etc., maximum depth 1,10 m for at least 1/3 of the pool surface;
• children's bathing pools, maximum depth of 0,60 m;
• multifunctional tubs allow for simultaneous use for different activities, or have convertibility requirements that make them suitable for different uses;
• the requirements for diving and underwater activity pools depend on the level of performance for which they are intended;
• swimming pools intended for therapeutic, thermal or rehabilitation purposes cannot also be used for recreational, training or sporting activities and the activities must be carried out under specialist health supervision.

From this it is clear that when you go to swimming pool at the spa, to lie around in a warm soak, you are in a recreational and not curative pool, where it is advisable not to swim too much, so as not to collapse from the heat. Also for this reason, these pools usually have non-rectangular shapes, but polylobate, with access steps, hydromassages, water games and other nice enjoyable gadgets.

It doesn't matter if the pool is public or private, what matters is if it is for public or private use. In this case we are interested in swimming facilities for public use.

Last distinction in paragraph 5, always of art. 2: swimming pools for public use and private swimming pools. Swimming pools are generally for public use; swimming pools that are part of single-family or two-family housing units are for private use, and their use, under the responsibility of the owner or joint owners, is limited to the members of the family and their guests..

Even though the 2003 Conference moved from single- and two-family homes to condominiums, it seems quite clear that in this case the emphasis is not on form, depth, or function, but on who is responsible in case of trouble. It goes without saying that if you go swimming in a public pool (which could also be that of a residence, a hotel, a campsite), there must always be someone on the pool deck to supervise. Usually these are lifeguards and swimming instructors, without them the pools would remain empty. They are just some of those responsible for the correct functioning of the facility, they are workers and for design purposes this must be taken into account, especially in terms of services, changing rooms and access to the pool deck, which should be separate from those reserved for practitioners and athletes.

Article 4, in addition to referring to specific attachments, pays particular attention to the distinction of spaces and paths, with little possibility of hybridization and with an absolute prohibition of any architectural barrier.
We find two other interesting things in art.5: the figure of the person in charge of technological systems, which in some way tells us that this is a specialized area almost in itself, subcontractable to specialized external companies, and the presence of the first aid room (the guarantee of accessibility of emergency vehicles to the system is also mentioned previously). These are two very different aspects that have one characteristic in common: the danger of the worst damages that can occur inside the swimming facility, damages that can derive from poor functioning, careless planning, or neglect. Obviously the part where we can make ourselves useful is that of planning.

Article 7 says something rather interesting (or pernicious) for the designer, it is there between the lines that passes almost unnoticed: Disinfection (daily) in these areas it will also have to extend to vertical surfacesThe areas in question would be those for swimming and bathing activities and in toilet facilities. The latter are not a concern, but the vertical walls of the pool deck are often quite high and difficult to clean. Even if you don't want to take it literally, it is good to think about a certain ease of periodic cleaning of walls and windows, as well as the storage areas for the related equipment, with sufficiently comfortable access routes to the pool deck.

Continuing in the annexes of the decree, the rule becomes even more stringent. As in other cases, precepts and minimum standards should not be understood as limitations, but as useful ideas for designing spaces.

Certainly measures and limits must be respected, but their general meaning must also be grasped in order to place oneself in a correct design perspective that can do better than respecting only the individual measures.
We report some of the provisions present in the annexes of the decree with the intent of promoting a careful and conscious approach to the design of these particular sports facilities in which it seems that there is absolutely nothing that can be left to chance, because here chance is almost synonymous with risk.

… allow easy visual inspection of all parts of the basin by supervisory personnel;
the washing water from the edge of the pool must not flow into the overflow channels of the pools;
flat spaces free from obstacles must be provided along the entire perimeter of the pool (perimeter platforms) with a width of no less than 2,00 m at any point;
in the perimeter areas of the pools at least one drinking water fountain must be calculated;
provide spaces that are distributed but directly connected to the body of water so as to allow users to stop ... in indoor swimming pools ... sized at least 0,6 times the surface area of ​​the body of water.

The perimeter spaces around the pool and those directly connected to swimming and bathing activities must be delimited by an impassable separation element from the surrounding areas.
The height of the pool compartment, measured from the free surface of the water, must not be less than 3,50 m at any point.

They are also prohibited in the changing rooms protrusions and sharp edges that may constitute a danger to the safety of users and staff; particular care must be taken in the choice and positioning of appliances and accessories (heating elements, water outlets, electrical outlets, handles, etc.).
…the changing rooms must constitute the element of separation between the shod path and the barefoot path.
The storage of equipment to be used in the pool must be directly accessible from the pool area.
The first aid room must be clearly marked and easily accessible from the pool and must allow for quick and easy communication with the outside through routes that can also be accessed using stretchers.

For indoor swimming pools, in the swimming and bathing activities section, the air temperature must not be lower than the temperature of the water in the pool.
The relative humidity of the air must not exceed the limit value of 70% under any circumstances. The air speed in the areas used by the users must not exceed 0,15 m/s and an external air exchange of at least 20 mXNUMX/h per square meter of pool must be ensured.
In other areas intended for visitors (changing rooms, toilets, first aid) the air temperature must not be lower than 24° C, ensuring an air exchange of no less than 4 volumes/h.

… the level of illumination on the walking surface and on the water surface must not be less than 150 lux at any point.
In all naturally lit environments, an average daylight factor of no less than 2% must be ensured.
In the swimming and bathing section of indoor swimming pools, the reverberation time must not exceed 1,6 seconds at any point. The noise level
generated by the systems and other installed sources must not exceed the limit of 50 dBA commensurate with the maximum environmental level.

Another important text to refer to is the CONI RULES FOR SPORTS FACILITIES – Approved by resolution of the CONI National Council n. 1379 of 25 June 2008.
In particular, we highlight art. 6.3 for rest areas, art. 7 for the heights of spaces on pool decks, lighting, orientation and attention paid to the possibility of glare from artificial lighting, ventilation, temperature and relative humidity, with references to specific tables and to the UNI EN 12193 standard. Art. 7.13 focuses on the routes between activity spaces and storage areas for cleaning, maintenance, set-up, etc. equipment, which must be as short as possible and free of differences in level.

The most important technical regulation in the sector, specific for public swimming pools, is UNI 10637 which contains guidelines for the design of the filtration, circulation and recirculation system of swimming pools in general.

It was created in 1997 in the wake of the aforementioned State and Regions Agreement of 1991, it was modified and integrated in 2006 and 2015 and today a new review process which should end at the end of 2022. 
At the moment, UNI 10637 applies in all regions that have not yet issued specific laws on public swimming pools. It contains specific standards for the plant systems of the pools and therefore concerns the design of the architectural organism up to a certain point.

Types and construction techniques of swimming pool basins

One of the features that differentiates the various types of swimming pools is the way in which the water that comes out due to the presence and movement of swimmers is recovered.

If a few people enter a pool full of water, a corresponding volume of water must come out, possibly without flooding the surrounding area. For this reason, there are various systems for recovering the water, which is then filtered, treated and reintroduced through outlets usually located on the walls.
While in small, normally private pools, surface recovery devices called skimmers can be used, for public pools over 100 m25 in surface area, i.e. all those we are interested in, those in which you swim that are 50 or XNUMX metres long, overflow systems are used. 
This system requires that the pool floor and the water are at the same level, the water overflows over the edge and falls into a perimeter channel normally covered by grids, from which it is conveyed into a compensation tank, from here it is taken by the filtering and treatment system which will then distribute it into the pool through the nozzles.
Different types of infinity pools are identified depending on the proximity of the perimeter collection channel to the edge of the pool, the covering of the channel with grids, or the use of slot systems, or under-edge overflow. The grids, usually made of plastic material, are perhaps the least aesthetically valuable solutions, but they have the advantage of easy inspection and cleaning.
Having clarified that the water will then return to the pool from the recovery channel (certainly filtered and treated...), it is also clear that it is not appropriate for the water and detergents used to clean and sanitise the entire pool surface to end up there, which should be conveyed elsewhere and then discharged.

Moving on to the structure of the tank and assuming a reinforced concrete foundation slab, different construction typologies can be defined for the perimeter walls.
A small, trivial consideration: if the tank is underground, the walls must resist the thrust of the ground towards the inside when the tank is empty, if it is above ground they must contain the thrust of the water towards the outside when the tank is full.
In any case, the walls and the bottom must reduce as much as possible the heat dispersion from the water to the outside.
The walls of the swimming pools can be made of bolted galvanized steel, with panels possibly covered in plastic material and also in stainless steel, but more often they are made of reinforced concrete poured on site, or with insulating formwork to be lost in blocks of high density polystyrene, or polystyrene, which facilitate both the construction and the elimination of thermal bridges. There are also pools in fiberglass, but they are normally small in size and are intended for domestic use.

The internal lining, which must always be light in colour, must also ensure the waterproofing of the pool.
Swimming pools often use tile coverings that are also well suited to defining the marked lines on the bottom of the pool at the center of each lane, but you can also use coverings with heat-sealed PVC membranes with different surface finishes that, unlike tiles, have fewer problems related to cracking at the joints. In any case, the aspect of waterproofing the pool and the elastic response of the covering to natural structural settlements are of fundamental importance and require careful installation, using quality materials.

Air conditioning and air treatment of an indoor swimming pool is a particularly complex matter and requires careful system design.

The starting data are that the air temperature must always be equal to or higher than that of the water, that it must be between 26 and 29°C and that there is a large production of water vapour, therefore the relative humidity tends to rise above the values ​​of 60-70% which precede conditions of discomfort for swimmers, staff and spectators, as well as producing phenomena of surface condensation especially on external walls and windows, or in any case colder ones.
Considering that the dew point temperature rises as the relative humidity decreases, that molds are particularly comfortable in warm, humid environments, that chlorine-based substances used to sanitize the pool water make the steam particularly corrosive, it is easy to understand how important the treatment of the air in the pool environment is, not only for the swimming structure (hygiene, maintenance, etc.), but also for the health of those who swim or work there, because respiratory problems, skin and eye irritations can arise.
But even less is enough for swimmers to feel “short of breath” just when they should be recovering, and this has a major impact on the quality of service perceived by those who pay to swim. It goes without saying that all this has repercussions when it comes to renewing the monthly pass, especially if there are other facilities nearby.

The issue is particularly complex and, as for the construction and waterproofing of the pool and the related systems, the advice remains to consult professionals and companies specialized in swimming pool systems.
The regulatory reference is the aforementioned State-Regions Conference of 2003, therefore on the pool surface: air temperature ≥ water temperature (24-30°C); maximum relative humidity 70%; air speed ≤ 0,1 m/s; minimum external air exchange 20 m10339/h per m20 of pool. In addition, if there are stands and spectators, integrate ventilation based on UNI 20. For changing rooms and services, minimum temperature XNUMX°C and air exchange XNUMX volumes/hour.

Dehumidification is achieved with systems based on a refrigeration cycle, or with the introduction of cold and slightly humid air in winter to be mixed with recirculated air, two different systems to be chosen also based on the location, because if outdoors in the cold months the fog is almost a constant, also the air will be too humid most of the time.
In all of this, the quality of the casing is important: good insulation and the absence of thermal bridges will mean less condensation.

The treated air (therefore hot and dry) should be introduced near the partitions with the outside that are colder and subject to condensation. A portion of the “new” air (approximately 15%) must also be directed onto the pool to “clean” it from chlorine vapors right where the swimmers breathe.
Air intake must always be far from the supply vents and it is advisable to have intake grilles both in the upper parts of the internal volume and at floor level to extract unwanted chemical substances. If there are stands, it is advisable to equip them with additional intake grilles, but not with supply vents that would make the area where people are dressed even hotter.
It is not enough to rely only on the doors to ensure that the air from the pool deck does not pass into the changing room and from there to the other areas of the facility, it is also necessary to regulate the state of depression between the different environments. By expelling more air towards the outside of the pool deck than that which is introduced, its air will tend not to invade the changing rooms, which in turn will have to be regulated so as not to expand their air to other areas with a lower temperature.

With all that is prescribed regarding water and air, you should be able to have a functioning system, but these are necessary characteristics that could almost be included in the firmitas of the swimming pool facility, that is, taking for granted that if a person goes swimming the water is decent, the air too, hygiene is not lacking and the facility will not collapse on him, but you use e Venustas they have yet to arrive.
The quality of the artifact will depend largely on the organization of the paths, which we have seen to be particularly important and clearly on the formal solutions that the architect will be able to implement following prescriptions that are detailed, but which are not numbers. For this reason we propose various design ideas among the cad drawings in download, in the image links and in further references.

Cover image taken from sporteimpianti.it

References 

• The brand new architect's manual; Mancosu Editore; First edition (September 1, 2019); edited by Carlo Mancosu, Luca Zevi, Bruno Zevi; pp. B 109, B 168-178, 
• CONI regulations for sports facilities – Approved by resolution of the CONI National Council n. 1379 of 25 June 2008 – https://www.federnuoto.it/home/federazione/settore-impianti/normative/norme-coni.html
• https://www.coni.it/images/impiantistica/Norme_regolamenti/DM_18.3.96.pdf
• https://www.swimmingpool.eu/it/consigli/11526-norma-uni-10637
• http://www.ciaumbria.it/attachments/article/92/UNI10637%202015.pdf
• https://www.eurospapoolnews.com/actualites_piscines_spas-it/64452-piscina,pubblica,norma,uni10637,gl11,circolazione,filtrazione,disinfezione,trattamento,chimico,acqua.htm
• https://www.professioneacqua.it/la-uni-10637-va-in-revisione/
• http://acqua-spa.it/la_piscina/tipologiamodellipiscine.html
• https://www.sporteimpianti.it/wp-content/uploads/2019/07/WHO-guidelines.pdf
• https://www.studiotermotecnicotrovato.it/blog-hvac/hvac-piscine-coperte/
• https://www.archilovers.com/projects/116434/piscina-comunale-a-taggia.html
• https://www.archilovers.com/projects/79659/piscina-comunale-sant-arsenio.html
• https://www.theplan.it/architettura/piscine-dello-stadio-terni
• http://www.vg-hortus.it/index.php?option=com_content&view=article&id=678:una-piscina-pubblica-nella-periferia-romana&catid=1:opere&Itemid=2
• http://www.passalevaassociati.it/portfolio/piscina-olimpionica-calenzano/
• http://www.spagnolcostruzioni.it/ampliamento-piscina-comunale-cordenons-pn/
• https://www.ispastrutture.it/referenza/copertura-piscina-carmen-longo/