Posted by Luis Cordeiro on

Swimming pool for public use - How to prepare a safe reopening from the maintenance point of view of the installation?

Following the Pandemic we live in today, the swimming pools for public use were closed to control the spread of the virus when the State of Emergency was declared.

However, a significant proportion of the complexes had already taken such action in advance.

From that time until now, we are all aware that the normality we knew will not return so soon.

We will have to learn to live with this new reality and create a different "normality", which will undoubtedly involve cross-cutting measures throughout society to minimise contagion from the new Coronavirus (SARS-CoV-2), and where procedures for social distancing and enhanced hygiene are always present.

It is in this perspective, that CIMAI, thanks to the capital of knowledge it possesses, both in the treatment of swimming pool water and in the development and production of disinfectants, acquired over more than 30 years of experience, looks to the reopening of our swimming pools.

So, in a direct way, what we can say when we look at a pool is that our central problem is not the pool water.

That is, from the chemical point of view, the swimming pool water, as long as it permanently has the disinfectant concentration between 1.0 - 2.0 mg/l and the pH below 8.0, complying with all other procedures, such as continuous monitoring of chemical parameters, adequate circulation, filter washing, etc., will certainly be in good microbiological conditions, so there is no need for any chemical shock treatment when the much desired reopening.

In that case the question may arise as to: why these facilities have not yet been reopened.

The answer is complex, as the problem of swimming pools for public use is related to the dry and humid spaces themselves, which provide physical proximity between users.

That's why changing rooms, swimming pool docks, benches and reception areas will always be spaces where there will be a high risk of contamination. It is not easy to maintain safety distances between users during circulation in a complex, and it is almost impossible to avoid frequently touching: handles, handles, light switches, shower mixers, etc ...

In addition to the above, there are scientific studies that argue that when physical exercise activity, where respiratory movements increase its frequency and depth, the risk of Coronavirus transmission increases.

But of all the areas of a swimming pool, those that certainly have a greater risk of contagion are certainly the changing rooms, because it is in these areas that many people circulate simultaneously and users repeatedly touch the same materials.

To make this situation worse, there is something that certainly increases the risk of contagion in the locker rooms. SARS-CoV-2, as we all know, is a respiratory virus, as such it is transmitted by small droplets (so small that they cannot be seen and can remain suspended in the air, or on hard surfaces for hours). Now, of course, in the changing rooms the amount of aerosols formed as a result of bathing in showers is very high, and since the transmission is also by aerosols that persist in the air, we are certainly faced with an environment where there is a high risk of contagion.

So what do we have to watch out for in a swimming pool to be able to reopen it safely, from a maintenance point of view?

  • Analyse in detail all the guidelines that the guardianship will issue, and comply with the instructions defined therein;
  • Draw up a new sanitation plan for the entire facility;
  • Put all equipment into operation and evaluate the need for additional treatment to the water plan. Confirmation of the microbiological quality of the water through laboratory analysis;
  • Maintenance procedures to the building water network of the facility. Confirmation of Legionella absence through research and quantification analyses;
  • Wash and disinfect, before opening, all spaces and surfaces with appropriate products and in accordance with the recommendations of DGS and WHO;
  • Other procedures considered necessary.

Analyse in detail all the guidelines that the guardianship will issue, and comply with the instructions defined therein;

We will not comment on the procedures of social distancing, occupation rates of the various areas, because there are entities with significantly superior knowledge to define which are suitable for each area, in order to safeguard the health and safety of all those involved and certainly the DGS will define which are mandatory and/or recommendable.

It will be the responsibility of those responsible to analyse them and implement them in the facility.

Draw up a new sanitation plan for the entire facility;

The current cleaning and disinfection procedure has to be safely reviewed and changed. In order to have a guaranteed disinfected facility, the frequency and the products usually used will certainly have to be replaced.

Therefore, those responsible should look across the entire installation, define operating procedures, frequencies, materials, products, personal protective equipment to be used, for cleaning and disinfecting the entire installation.

This plan should be drawn up in accordance with the guidelines of the DGS, but also with the collaboration of the professionals concerned. Only in this way will we have a team duly committed to what needs to be implemented in practice.

For example, in accordance with the DGS guidelines, the frequently touching surfaces should be cleaned at least 6 times a day, but it may even be necessary to increase this frequency.

Put all equipment into operation and evaluate the need for additional treatment to the water plan. Confirmation of the microbiological quality of the water through laboratory analysis;

In addition to putting all equipment into normal operation, records of disinfection and pH levels should be evaluated during the time the plant is closed.

As we have said before, as long as the pool water has had at all times the concentration of disinfectant between 1.0 - 2.0 mg/l and the pH below 8.0, complying with all other procedures, such as continuous monitoring of chemical parameters, proper circulation, filter washing, etc., there will be no need for any chemical shock treatment.

In the event that the pool water treatment systems have been interrupted, a shock treatment following the ratio CxT = 255, where C is the concentration of free residual chlorine in ppm and T the contact time in hours (for pH=7.5 and Temperature=25º C).

It is, however, necessary that before opening, collections are made by an entity duly accredited for this purpose in order to perform the physical-chemical and microbiological analyses defined in standard NP 4542:2017, and thus attest to the quality of the pool water.

Empty, clean and disinfect the sanitary hot water circuit. Confirmation of Legionella absence through research and quantification analyses;

With the closure of the swimming pools for public use and other facilities, we created a potential risk in our facility: the development of micro-organisms in water circuits, in particular Legionella and others.

Therefore, operations to prevent and mitigate this risk should be carried out in both the cold and hot water circuits.

These procedures have to be adapted to the procedures carried out during the closure, i.e. the installations where water discharges continued have a much lower risk potential than those that were completely stopped.

Cold water circuit:

The vast majority of facilities where there are swimming pools for public use, are supplied directly by the municipality's water distribution company, and do not have cisterns or water storage tanks, so this is an advantage, as it is one less critical point. Those who have these tanks should clean and maintain them in accordance with DGS guidelines.

In the rest of the network, disinfectant should be injected if possible in order to reach the end points with at least 20 ppm of chlorine, and all end points should be opened regularly.

Hot water circuit:

It is true that part of the installations opted to turn off the heating systems and no longer have domestic hot water, but they have stopped water in the installation, which greatly increases the probability of Legionella's development.

Therefore, and to mitigate this risk in the installation, we will have to adopt certain preventive procedures, namely:

  • Emptying the sanitary hot water tanks and washing them, if possible, in accordance with DGS guidelines;
  • Dismantling all perlators/filters of taps and showers, cleaning and disinfecting them with a chlorinated disinfectant duly notified to the DGS;
  • Filling the deposits and thermal or chemical disinfection of the whole system, following the procedures already defined by the regulatory authority;
  • Confirmation of the absence of Legionella by laboratory tests at an accredited body.

Wash and disinfect, before opening, all spaces and surfaces with appropriate products and in accordance with the recommendations of DGS and WHO;

As far as disinfection is concerned, we will advise what from a technical point of view is best suited to the various areas in order to ensure a safe environment for those who frequent it and for those who carry out their professional activity there. Our technical advice is based on the guidelines of the DGS and WHO at the time of drafting this document, as well as our experience in this area.

The new Coronavirus (SARS-CoV-2) can be transmitted by direct contact and indirect contact, through droplets expelled to surfaces.

In light of current knowledge, it is thought that SARS-CoV-2 can remain on surfaces for at least 48 hours.

All surfaces can be vehicles of contagion, but the risk of this contagion varies depending on the frequency of handling, touch or use. The surfaces with the greatest risk of transmission are those that are frequently touched, i.e. those handled or touched by many people and very frequently, throughout the day. Examples of these surfaces are: door handles, light switches, elevator buttons, shower mixers, washbasin taps, toilet handles, tables, countertops, chairs, handrails, teaching material, benches and lockers, among others.

Therefore, and looking at the usual typology of the facilities, we have 4 different types of areas for which a detailed hygiene plan must be drawn up.

  • Pool Pier;
  • Common Areas (reception, sanitary facilities, etc);
  • Locker rooms;
  • Technical areas (exclusive to teachers or maintenance staff).

In this document we do not intend to detail the sanitization plan, but only to leave some recommendations that may serve as a basis for the procedures to be implemented before the opening and that may also help in the elaboration of the future sanitization plan of the facility.

We draw attention to the benefits of natural ventilation of any space in the facility, where this is possible.

Pool Pier

This is a barefoot area in which we should pay particular attention to cleaning and disinfecting the following areas:

  • Floor;
  • Didactic material;
  • Foot-washer shower;
  • Other materials (seats, hangers, etc.);
  • Other areas (walls and glass);


The paving of the pool pier, facing the proximity of the water plane, should be washed and disinfected with a product that is not incompatible with the water of the pool itself, i.e. that does not react with the chlorine of the water. In addition, it must be low foaming.

The frequency of this cleaning and disinfection should certainly be increased. Ideally, hygiene should be carried out after the end of each hour of use, however, given the size of most spaces, this will certainly not be possible. Alternatively, compulsory footpaths for access to water plans can be created and daily disinfection can be reinforced on these footpaths, particularly after each hour of use. In this case, an overall disinfection of the pool quay can be considered, twice a day.

For the pool pier, our technical advice is to use a chlorine-based product, which we know to be effective in inactivating the new coronavirus and other viruses, bacteria and fungi.

Didactic material

The disinfection of this material was already particularly important, but now it is even more important, since it is material that is used by different users, so in our opinion it should always be disinfected after use.

Since the educational material is intended to be in contact with swimming pool water and people, a product that is innocuous should be used when the material comes into contact with water. We therefore recommend a chlorine-based or hydrogen peroxide-based product.

Foot wash shower

The foot-wash showers should not have standing water, this should be drained automatically after each passage. Since this is a frequent passage area, it should be properly sanitized, with the same periodicity as the pool pier. The product to be used on the floor should be the same as the floor of the quay and the remaining areas should be sanitized with products suitable for the materials to be disinfected.

Other materials (seats, hangers etc)

The continuity of the existence of this type of material, which is also frequently touched by users, should be considered by those responsible.

The safest way is surely to remove them at this stage. If you choose to keep them, they will have to be subject to frequent disinfection. Depending on the type of material, a chlorinated base product, hydrogen peroxide or alcohol can be used.

Other areas (walls, glass, etc)

These will be the areas with the lowest probability of contagion, yet they should be sanitized on a daily basis, and the choice of products to be used will depend on the type of materials they are made of, but they should be chlorinated, peroxide or alcohol-based.

Common Areas (reception, sanitary facilities, etc.)

Before we go into the disinfection of these areas, the rules of the frequency of the space and the procedures to be adopted, by employees, users and accompanying persons, should be defined.

Measures to ensure social distancing as well as adequate individual protection for each zone should be clearly considered and disclosed.

In terms of common areas, it is normal to have 3 distinct areas:

  • Reception;
  • Benches;
  • WC´s.


This is an area that is usually quite near the entrance. Therefore, it will be important to ensure that disinfectant is available at the entrance, so that all users and visitors to the space can thus proceed to their hygiene as soon as they enter the facility.

All areas of frequent touch, such as desks, door handles, switches, lift buttons and others, should be properly disinfected at least 6 times a day. In the case of systematic touch surfaces, such as door handles, and in accordance with the DGS guidelines, they should be sanitized on an hourly basis. The choice of products to be used will depend on the type of materials they are made of, but they should be alcohol, chlorine or hydrogen peroxide based.

The floor and glass should be washed and cleaned at least twice a day, and the walls at least once a day.

Here, as above, the choice of product type will depend on the materials to be sanitized, and in these areas the ideal will always be a solution containing detergent and disinfectant.


Depending on the guidelines that the authority will issue for the occupancy rate of the facility, they should take this into account in order to define the occupancy rate of these zones as well.

In accordance with DGS guidelines, chairs/stands should be sanitized with alcohol or hydrogen peroxide products whenever users leave.

Sanitary Facilities

The toilet facilities should be washed at least 3 times a day, preferably with products containing detergent and disinfectant, in which case a chlorine-based product is most appropriate.

The frequent touch zones in WCs should follow the above mentioned instructions, both with regard to products and frequency.

In these areas the existence of hand washing products must always be safeguarded, and the solution may also pass through a product that in addition to washing, also disinfects.


As we said before, this is the most sensitive area in the facility. The usual rate of occupancy of the changing rooms, combined with the conditions of the changing room, means that concern about this area is particularly high.

It is expected that when the facilities are reopened, these areas will still be banned for some time, but we will have to wait for the guidelines that will be given by the DGS.

Surely the instantaneous capacity will have to be lowered and the frequency of sanitization will have to be strongly increased.

In a bathhouse, removing the walls and ceilings, all the other areas end up being in frequent contact. And even the walls and ceilings, due to the enormous rate of aerosols generated inside the changing rooms, are surfaces that can easily be contaminated. Therefore, with regard to the frequency of sanitization of these spaces, all the guidelines to be defined by the DGS will have to be followed. The products must be suitable for the materials to be sanitised and in accordance with the frequencies laid down.

Depending on the guidelines that the authority will issue for the occupancy rate of the facility, they should take this into account in order to define the occupancy rate of these zones as well.

Technical areas (exclusive to teachers or maintenance staff)

These areas are restricted, however we still have frequent contact surfaces (already listed above) and others.

Teacher's rooms

In the case of areas reserved for teachers and other pool pier professionals, the areas of frequent contact should continue to be sanitized at a frequency of 6 times a day, or another that is appropriate to the rate of occupation of these areas.

The remaining areas such as floors, windows, etc. should be cleaned and disinfected at least once or twice a day.

Technical equipment areas

Depending on the size of the installation, this is an area normally attended by 1 or 2 maintenance technicians only.

Therefore, even the so-called "frequent contact zones" do not have such frequent contact, so that, except for other indications from the DGS, it will suffice to ensure their disinfection once a day.

Cleaning of other surfaces, such as the floor and others, should also be done once a day.

In any of the restricted areas mentioned above, the products selected must be suitable and compatible with the materials we intend to sanitize.

Other procedures deemed necessary

Specific procedures, which from the point of view of the maintenance of a specific installation, prove necessary.

Heights of uncertainty are usually generating new paths and opportunities, so we are all called to look at the facilities from a new perspective and think "outside the box".

This is the time to go further, to do it differently, putting everyone's safety and health first!


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