Reopening Your Spa & Hot Tub Facilities After COVID-19 Shutdown

As we are getting closer to COVID-19 restrictions being lifted in many countries, the long wait is almost for spas and hot tubs to open to the public. Over the past year in the UK we have seen a rise in the popularity of staycations to holiday homes and cabins with hot tubs.

We have collated the guidance from Public Health England and PWTAG on operating commercial spas and hot tubs to help you to understand what is required to help you reopen your facilities.  All recommendations are based on local guidance, we always recommend you seek advice from your local advisory board.

For a full guide on reopening your leisure facility including your pool please take a look at our reopening your pool guide.

COVID-19 transmission in hot tubs and spas

Hot tubs are designed so that individuals sit in close proximity facing each other. Current evidence demonstrates that coronavirus is primarily transmitted through contact and inhalation of respiratory droplets. An individual who is infected can emit droplets containing COVID-19 when they cough, sneeze, talk or laugh. The droplets will be a mixture of small aerosol droplets (<5 microns) and large droplets (>10 microns).

The smaller aerosol droplets can stay airborne for hours and can be transported long distances by the wind, whilst the large droplets will fall under gravity from the infected person. Therefore, in a hot tub setting the virus will fall either into the water or potentially in front of another individual. There is a possibility that the air-jet circulation in spas will increase the risk by spreading contamination through aerosols generated directly from the pool water.

Spas have a much higher bather load to the volume of water. Hence the spa water will be subject to a higher concentration of organic material from bathers. Contaminated aerosols are therefore likely to be generated even when the spa is unoccupied.

Reopening your spa or hot tub

With your spa or hot tub closed for a prolonged period you would have likely opted to drain the water or keep it running. If your spa facility has remained empty for the last 4 months, then you will need to meticulously clean and disinfect it. Whilst if you have kept it running you will need to super chlorinate to 50 mg/L and then empty. This thoroughly cleans your spa and ensures that any bacteria or contaminants in the water are removed. Your testing equipment may not be able to test up to this level of chlorine, and therefore a dilution method will be required.

To conduct a dilution, you will require a dilution tube. Fill the dilution tube to the necessary mark, for example x2 with water from the spa. Then top up to 100 mL using deionised water and 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 from your photometer and times it by dilution factor (e.g. x2). For further guidance on dilution procedure watch our instructional video here.

Dilution Calculation: Test Result x Dilution Factor

PWTAG have set out some specific points to consider when reopening your spa or hot tub:


  • Remove and flush any existing water including the balance tank
  • Disinfect and clean the removable jets and internal user facing surfaces
  • Remove any built-up scaling


  • Once refilled with fresh water you need to keep the pH level of the water as close to 7.0 as you can to conduct your super chlorination to 50 mg/L for at least 1 hour
  • Ensure circulation is at full operation, including all jets and blowers, to ensure the disinfection is being circulated correctly
  • Once the hour is over thoroughly empty all pipework and the spa
  • Return to routine operation

A best practice tip when refilling your spa is to use rapid dissolving calcium hypochlorite or sodium hypochlorite solution at 5 mg/L as this will ensure that all pipework is chlorinated as the water levels rise.

Once you have filled your spa, a microbiological test will need to be conducted. This includes legionella as the risk of legionella contamination is increased when the spa has been inactive for a prolonged period of time.

Hot tub and spa operation after COVID-19

How is bather load affected?

Historically bather load in hot tubs and spas is dictated by the size and seating of the spa. Under the “new normal” spa capacity will also need to consider social distancing. This may mean that bather capacity in spas will be reduced and could even be limited to use by one person at a time.

It is advised that individuals only use the hot tub for 15-minute sessions, with a 5-minute interval to allow for optimum disinfection to be maintained.

Bathers should disinfect or wash their hands prior to entering the building and should be encouraged to take a shower prior to using the facilities. This will enable the available disinfection to focus on COVID-19 rather than other contamination introduced by the bather.

How often does the water need replacing?

Under HSG:282 the importance of replacing water is highlighted. In a commercial setting, once the spas have reached number of bathers 100 times the volume in m3 the water needs to be replaced. For more information on spa chemistry, HSG:282 and testing watch our webinar here.

For hot tubs and spas used as a business activity (rentals, holiday lets, etc.) the water should be replaced after each rental, or weekly, whichever is sooner.

Disinfection & testing of your hot tub

It is widely agreed among experts that adequate disinfection of the water will render COVID-19 inactive and hence the risk of catching the virus from the water is significantly reduced. Risk is further reduced when the virus becomes diluted in the water. The main risk remains from airborne aerosols and contaminated surfaces.

Current evidence demonstrates that with the correct pH and disinfection levels the virus should inactivate within 15-30 seconds once in contact with the water. PWTAG advise that lower pH levels make it easier for the chlorine to kill microorganisms. To ensure sufficient disinfection, it is advised you maintain a minimum of 3.0 mg/L of chlorine residual and 4.0 mg/L for bromine. pH levels should be kept as close to 7.0 as possible for effective disinfection. Should the pH levels increase so should the disinfection. Combined chlorines should be as low as possible and never exceed 1.0 mg/L.

UV light can inactivate chlorine making it less effective at disinfection; cyanuric acid is used to protect the chlorine molecules from the UV light. However, cyanuric acid also reduces the efficacy of free chlorine, requiring significantly more contact time to kill a range of pathogens. Although no testing has been done to see the effects of this in relation to COVID-19 it is reasonable to assume this is the case.

Therefore, it has been recommended by PWTAG that during these uncertain times spas dosed with cyanuric acid should ensure that the levels do not exceed 100 mg/L and that free chlorine levels remain at least 5 mg/L. You may have to replace more water than often to lower the cyanuric acid levels.

Testing is essential to ensure you are maintaining the disinfection residual and optimal pH levels. Free chlorine, combined chlorine and pH should be tested as a minimum at the beginning of the day and every two hours after.

Secondary disinfection helps to remove pathogens and contamination that are not affected by primary disinfection. It is advised that you still adhere to the disinfection and pH levels discussed regardless of whether secondary disinfection is used or not. Primary disinfection residual is crucial for deactivating COVID-19.

Circulation of your spa

To reduce the risk of the virus being transmitted there should be:

  • Sufficient primary disinfection residual to denature the virus
  • Sufficient dilution of the virus in the water

Maintaining circulation at 100% will ensure sufficient dilution of the virus in the water, as well as distributing the primary disinfection.

Modern spas come with an array of booster and air jets which offer a range of health benefits. However, in current circumstances the operation of these poses a potential risk of COVID-19 to bathers. The risk can be reduced by regularly circulating chlorinated water and disinfecting the air jets with a 50 mg/L solution of free chlorine at least once a week.

Cleaning of your spa and leisure facilities

Prior to reopening a full deep clean of the facility should be done. Regular cleaning requirements will be increased in both around the spa and the changing rooms (if shared facilities). It is up to the operator to determine how this fits into the operating procedures.

When operating multiple spas, dedicated cleaning apparatus should be used for each spa to reduce cross-contamination. Hot tubs that operate with cartridge filters should be washed at 60⁰C or replaced. Filters should then be soaked in a chlorine solution, and dried before reinstalling them.

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

Palintest is always here to offer guidance and support your pool and spa testing needs, if you have any further questions please contact our team by filling in the form below.

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