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How To Prepare For Reopening Your Pool Facility

April 20, 2021 0 Comments

How To Prepare For Reopening Your Pool Facility

Over the last few months, many pools and spas have been closed due to COVID-19 restrictions. With summer approaching in the Northern hemisphere and the reopening of leisure facilities getting nearer we have collated guidelines from the CDC in the US, PWTAG in the UK, and Swim Australia, helping you to understand what is required to reopen your pool facilities. As always, regional differences do apply, so please check with your local governing body for further guidance.

What are the risks associated with COVID-19 and swimming pools?

It is widely agreed from experts that the risk of catching COVID-19 from a swimming pool is minimal. Research from various countries including America, the UK, and Europe, agrees that pool water is safe when maintaining chlorine levels at 1.5 mg/L (or above) and pH levels between 7.0-7.4. This is because when the virus enters the water it becomes diluted and the active disinfection renders the virus inactive.

Effective testing and management of your pool facility can ensure that the water remains safe for pool users. Management of external facilities is also critical, with guidance on this provided in the final section of this article, see Maintaining safety in pool and leisure facilities after COVID-19.

Understanding pool water chemistry

Whenever pools have been closed or inactive for a prolonged period, more attention should be given to your pool water chemistry to ensure bather safety and to protect the infrastructure of the pool facility.

With your pool closed for the last few months, you would likely have opted to either:

  • Drain the pool water;
  • Stop water circulation;
  • Reduce circulation and regular monitoring of water chemistry

Chlorine shock treatment and dilution

When your pool facility has been closed or not in use for some time, it is typical that you administer a shock treatment. A shock treatment involves a high chlorine dosage to thoroughly ‘clean’ the pool and ensuring that any bacteria or contaminants in the water are removed.

PWTAG advise dosing your pool with up to 20 mg/L of chlorine to deactivate any bacteria or virus within the pool water and system. As these levels are not typical for standard pool maintenance, your testing equipment may not measure chlorine at these higher levels and therefore you will be required to perform a dilution of your sample. We recommend using a dilution tube for this to ensure accuracy. Fill the dilution tube to the necessary mark, for example x2, and top up to the 100 mL using deionised water, then mix the solution. The dilution is now complete and this sample can be used as the new blank sample and for the test sample. To calculate your result, take the reading on the photometer and times it by dilution factor (e.g. x2). After the shock treatment, normal chlorine levels should resume. Watch our instructional video showing you how to perform a dilution here.

Dilution Calculation: (Test Result) x (Dilution Factor)

The WHO suggests that a residual concentration of free chlorine of 0.5 mg/L or more is sufficient to eliminate enveloped viruses. However local bodies are suggesting a minimum 1.5 mg/L. PWTAG recommend maintaining chlorine levels at 1.5 mg/L or above to ensure that you remove the risk. For pH levels, PWTAG recommend maintaining levels between 7.0 and 7.4, with 7.2 the optimum pH for effective disinfection. As COVID-19 is still an evolving situation, local guidelines may change and it is advised that you check with your local authority about disinfection and pH levels.

Once disinfection and pH levels are normalised, normal practices can resume, this includes automatic dosing, secondary disinfection (e.g. UV or ozone), and heating. As the water reaches the optimum temperature, you should take the final tests including:

  • Microbiological
  • Free and combined chlorine
  • pH
  • Total Alkalinity
  • Calcium Hardness
  • Cyanuric Acid (if present)
  • Total dissolved solids

Once these tests meet local guidelines, pools can be reopened to be public.

How to maintain your pool water chemistry

Initial testing is critical for ensuring that your water is safe for bathing after prolonged inactivity or pool closure. However, each commercial pool should have a regular testing procedure to minimise risk and ensure that the pool is always safe for bathers. Regular testing of your disinfection and pH will ensure that any coronavirus and other microorganisms remain inactive in the water. Other parameters you should consider are:

Calcium Hardness:

Calcium Hardness is a measure of how corrosive your water may be. In water with elevated levels of calcium hardness, white deposits will form and leave your pool prone to scaling.  If calcium hardness levels are too low, then it becomes corrosive and can start to attack your fixtures and fitting, damaging the pool infrastructure and integrity.

Cyanuric Acid

Cyanuric acid is usually referred to as stabiliser, protecting chlorine molecules from degrading caused by UV light. Cyanuric acid provides a shield around the chlorine molecules to ensure it remains at its optimum disinfection potential. This is not used in all pools and therefore testing is not required for all pool facilities.

Total Alkalinity:

Total Alkalinity is critical for ensuring pH levels remain stable. All things have a specific pH including pool chemicals and even bathers. Maintaining pH helps ensure that disinfection can be effective. Total alkalinity acts as a buffer to prevent dramatic changes in your pH. If the total alkalinity level is too high, then the pH levels become too resistant to change, which in turn can make disinfection less effective.

Total Dissolved Solids (TDS):

A high level of TDS can demonstrate a deteriorating water quality.

Water Balance testing

Testing for pH, disinfection, total alkalinity, calcium hardness, cyanuric acid and TDS, all form part of the water balance calculation, which can be done using either the Langelier Saturation Index or the Ryznar Index.

Other test parameters can also be useful in determining the safety of the pool to protect both the bathers and pool infrastructure. Widespread testing is proven to be both cost-effective for treatment and safer for pool users. Other parameters which are also recommended for testing include:


Microbiological testing is arguably more critical than ever during these unprecedented times. For microbiological testing, water samples are usually sent to your local laboratory for analysis.


Phosphates are naturally present in water and can be introduced by the environment from soil and twigs, and also through bathers from hair and body products. Phosphates are a food source for algae and can turn your pool water green.


Turbidity is a measurement of how cloudy your water is. Turbidity is used as a general water quality indicator across many sectors including for drinking water. High turbidity levels can indicate issues with your water treatment management and can make for a less enjoyable experience for the bather. More critically, high turbidity can be a safety risk if the lifeguards cannot see the bottom of the pool which would force the pool to be closed.

Recommended test limits for pools

Below is a quick guide to recommended parameter levels proposed by PWTAG. We have also provided recommendations for testing frequency based on our own industry experience.

Palintest recommendations are based on industry knowledge, industry guidelines and best practice, however local guidelines will vary and therefore you should always check your local authority to ensure local compliance.

Parameter PWTAG – UK Palintest Recommended Frequency
Combined Chlorine <1 mg/L Daily
Free Chlorine 1.5 – 3.0 mg/L Daily
pH 7.0 - 7.4 Daily
Calcium Hardness 80 - 200 mg/L Weekly
Cyanuric Acid* <100 mg/L Weekly
Total Alkalinity 80 - 200 mg/L Weekly
TDS** <1000 mg/L Weekly
Phosphates <0.01 mg/L Monthly
Turbidity <0.5 NTU Monthly

*Cyanuric Acid – although cyanuric acid does protect the chlorine molecules from UV light, it does reduce disinfection efficacy of free chlorine, which increases the time required to destroy pathogens. If cyanuric acid is used, PWTAG suggest that levels remain lower than 100 mg/L and that a minimum free chlorine of 5 mg/L is maintained.

**TDS – source water will vary between regions, with TDS usually between 500-1000 mg/L. The general rule is that your TDS should not rise more than the recommended level above your source water and should not exceed 3000 mg/L. When operating salt water pools, TDS levels may be higher. For more information on how to test salt water pools click here.

Preparing your Pool Testing Equipment

If your pool has been out of use, it is also likely that your pool equipment has been inactive. For test equipment including photometers, effective maintenance is key to maintain optimum performance.

Before starting your testing process, we would advise you to complete a full check of your testing equipment to ensure it is still functioning correctly. A thorough clean of your equipment should be completed before use. For your photometer, we would advise you to clean the optical area of your instrument to remove any contamination.

By using check standards, you can verify that your photometer is still within calibration; enabling you to have full confidence in your test results. A complete clean should be completed before running your check standards as any dirt or residue in the optical chamber may affect the result. If your check standards fail or if your instrument needs a recalibration, then please contact us to discuss the options. You can find more information about this service here.

Maintaining safety in pool and leisure facilities after COVID-19

Palintest is proud to be recognised as testing experts in the pool and spa industry, however we are aware that pool testing is only one part of effective pool management. Therefore, we coordinate with other industry experts to ensure that we can offer you the best information to ensure effective management of your complete leisure facilities post COVID-19 lockdown.

What facilities can be reopened?

COVID-19 is a respiratory virus, meaning it is transmitted through the air. Therefore, the likes of whirlpools, spas, water slides and other recreational elements are seen as a higher risk. As coronavirus can be transmitted through the air, these types of leisure facilities are more prone to providing aerosols into the air enabling the virus to travel. For this reason, the CDC and many other authorities have advised that these facilities should remain closed.

Social Distancing in Swimming Pools

Whilst the swimming pool water is disinfected and protected, social distancing is still important to ensure that the virus does not spread between bathers through the air. All pools must define a new bather capacity to ensure swimmers have enough room to ensure they can maintain social distancing. It is advised that you check with your local authority on social distancing guidelines.

Through effective disinfection and filtration, the virus can be inactivated quickly. Maintaining your circulation at 100% distributes the free chlorine to minimise the risk of infection and ensures good dilution of any released virus particles.

Maintenance of your wider pool and leisure facilities

Receptions, changing rooms, entrance/exit areas, restrooms, lockers, drinking fountains, handrails, shared pool equipment and showers are seen as high-risk areas for the public. Social distancing guidelines remain in many countries and these must be followed especially in high traffic areas. Swimming Australia and other authorities have advised against any large gatherings when possible, including: swim parties, swim classes, group training.

As always seek local guidance on social distancing including recommendations on larger gatherings. For many regions, these guidelines are changing frequently and pool owners must review regularly to ensure local guidelines are met at all times.

Maintaining showers, lockers, wash facilities and drinking fountains

The availability of showers and lockers should be reduced, ensuring that each unit has at least one inactive unit in between active ones. This ensures that social distancing can remain and makes it easier to identify areas which require more frequent cleaning. As with all public facilities, cleaning frequency should be increased; with a focus on disinfecting frequently touched surfaces like door handles, changing rooms, lockers, toilets, showers, and handwashing facilities. To help maintain your cleaning regime, look to introduce cleaning times between swim sessions when the public is not within the facility. For example, having 1-hour slots every 1.5 hours to ensure you have 30 minutes to disinfect between each group of swimmers.

Drinking fountains, showers and other facilities should also be checked before reopening. The risk for legionella contamination is increased when these facilities have been inactive. To ensure there is no Legionella risk, a sample should be sent to your local testing laboratory, with disinfection completed before reopening.

It is essential that any indoor pool has good ventilation to reduce risk from aerosols that may contain COVID-19 viruses. Where feasible, facilities should try to introduce as much fresh air from outdoors into the facility to help circulate the air.

It is recommended that facilities should prevent supplying towels where possible. If towels are supplied then these need to be washed after each use at 60⁰C or the warmest setting appropriate.

Safety of staff and the public in pools

As per WHO guidelines, vulnerable staff and customers should refrain from returning to any public facility. If a member of staff or the public show symptoms of COVID-19 they should not enter the facility and follow local government guidelines on testing and isolation.

As mentioned earlier guidelines can differ between regions so Palintest always recommends that you seek advice on your local authority legislation.


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