How to safely reopen spa pools and hot tubs after COVID-19

Since the early weeks of the COVID-19 pandemic, various pieces of guidance have been released to support the management of spa pool and hot tubs. As we once again face the gradual move out of lockdown, we wanted to summarise that information for you.

We focus in particular on the latest guidance from PWTAG Technical Note 47. The information here offers excellent advice on managing the risks associated with Legionella and COVID-19 from spa pools and hot tubs. We would suggest reading through this guidance prior to addressing the chemical requirements set out below.

Reopening after prolonged periods of disuse

It is likely that your spa or hot tub has been closed for a prolonged period and that you have drained the water to keep it operational. If it has been empty for the last four months or more, you will need to thoroughly clean and disinfect the system. If you have kept it running, you will need to super chlorinate to 50 mg/L and then drain.

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

1. Cleaning

To clean your spa or hot tub effectively you will need to carry out the following steps:

  • Remove and flush any existing water including the balance tank
  • Disinfect and clean the removable jets and internal user-facing surfaces using Sodium Hypochlorite (BV102), Chlorine Dioxide (BV1304) or Sodium Bicarbonate
  • Remove any scale build-up

At B & V Chemicals, we have a range of cleaning products suitable for the spa surfaces, pipework and surrounding areas, as shown in the table below.

Cleaning chemicals
Spa Surface Cleaner
An easy to apply and effective cleaner to clean waterline and surrounding surfaces of pools and spas.
Spa Foam Away
Use to prevent and destroy unsightly foam on the surface of spa pools.
Spa Flush
Used regularly prior to draining, spa flush will ensure pipework and internal spa surfaces is clean and free of soap, oil, and biofilm.
Deck Cleaner
A cleaner for decking, walkways, and surrounding surfaces. Use as required.
Multitreat SHD (Indicator)
All-in-one a cleaner, de-scaler and disinfectant for showerheads.


2. Refilling

The next step is to refill the spa or hot tub:

  • Once refilled with fresh water you will need to keep the pH level of the water as close to 7.0 as possible to conduct the super chlorination to 50ppm chlorine (BV102) for at least 1 hour
  • Ensure circulation is at full operation, including all jets and nozzles, as this will ensure the disinfectant is being circulated correctly
  • After the 1-hour period is over, thoroughly empty all pipework and the bulk water
  • Return to routine operation, paying attention to the manufacturers and required control parameters for the unit and its water content.

A best practice tip when refilling your spa is to use rapid dissolving calcium hypochlorite (BV21) 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 testing, as the risk of Legionella contamination is increased when the spa has been inactive for a prolonged period of time.

3. Disinfection and testing

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

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 of 7.0 – 7.4 provide ideal conditions for chlorine to be most effective at killing microorganisms. To ensure sufficient disinfection, it is advised you maintain a range of 3.0 – 5.0 mg/L of chlorine residual and 4.0 – 6.0mg/L for bromine.

B & V’s sanitising chemicals, such as those listed below, can be used here.

Sanitising chemicals
Spa Bromine tablets
A slow dissolving tablet form sanitiser designed to maintain a consistent level of bromine.
Spa Bromine Granules
A highly effective granular bromine-based sanitiser that will kill and prevent bacterial and algal growth.
Spa Non-chlorine shock
A granular non-chlorine potassium monopersulphate shock treatment used to increase the effect of bromine without contributing to chlorine levels.
Spa Chlorine Dioxide tablets
An effervescent Chlorine Dioxide tablet designed for rapid effect disinfection of spa pools.
Calcium Hypochlorite
A granular Calcium Hypochlorite treatment for continuous and shock treatment of pools and spas.
Sodium Hypochlorite
A liquid sodium hypochlorite product for continuous and shock dosing of pools.

The pH levels should be kept as close to 7.0 as possible for effective disinfection and ideally in the range of 7.0 – 7.6. Should the pH levels increase so should the disinfection. However, products are available to help lower and balance the pH level, such as Spa pH minus (BV184).

B & V's full list of balancing chemicals include:

Balancing chemicals
Spa pH minus
A product to decrease pH to within the desired range of 7.0 - 7.6 to reduce scale formation, cloudy water and increase sanitiser effectiveness. 
Spa pH plus
A product to increase the pH to within the desired range of 7.0 -7.6 to reduce corrosivity, staining and increase sanitiser effectiveness. 
Spa Soft Scale Inhibitor
Used where the calcium hardness of the water exceeds 200mg/l to prevent scale deposits and cloudy water. 
Spa Hardness Increaser
Used to increase calcium hardness where the calcium hardness of the water is less than 200mg/l to reduce corrosivity, staining and foaming. 
Spa Clear Liquid
Keep water looking crystal clear with this easy to use clarifying liquid. 
Spa Clear Powder
Keep water looking crystal clear with this easy to use clarifying powder. 
Spa Total Alkalinity Increaser
A total alkalinity increaser to raise total alkalinity in water that is below 80mg/l. 

This is a brief summary of the basic requirements and products that could be used in reopening your spa pool or hot tub. The PWTAG offers detailed guidance on how to successfully reopen your facilities should you wish to learn more.

B & V Chemicals are happy to offer any support and guidance you need to ensure your spa pool or hot tub is safe for users. You can get in touch with us here.

Shane Lynch

Shane Lynch

Shane Lynch has been in the Water Treatment industry for 15 years, specialising previously in industrial water treatment applications. He is now working as a sales and support consultant for the B & V Chemicals team, offering customers technical and specialist product support.

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