Testing Your Hot Tub and Spa

Why is regular hot tub and spa testing is required?

Whether you have a hot tub, commercial spa, or an inflatable hot tub, ensuring the highest water quality is essential. Like swimming pools, strict regimes around water testing are required for your spa.

Spas are becoming increasingly popular in the domestic and commercial market as a cheaper alternative to swimming pools, providing relaxation and medical benefits to users. With the increased risk around infectious diseases in spas, it is crucial that a strict testing and monitoring regime is in place. Like pools, the frequency of water testing will be flexible depending on the usage and location of the spa. Increased bather load will require more frequent testing. Your operating procedure will include daily, monthly and/or quarterly actions to ensure the highest water quality.

Hot tub and spa testing regulations

As always, regulations vary by country, region and sometimes system. In the UK, new guidelines HSG282 have been released to help the control of legionella and other infectious agents in spa-pool systems. The minimum key parameters under HSG282 in which you should test for:

  • pH
  • Disinfection (e.g. Chlorine, Bromine)
  • Total Dissolved Solids

When testing your spa-pool, you need to take samples at three different times to ensure good water quality. The first is when the jet functions are not in operation, and the second when they are. The final sample should be taken after the maximum use of the spa. The water chemistry will be affected by the jet systems and by bather load.

What tests you should be performing on your hot tub and spa?

As mentioned above, the minimum key parameters under HSG 282 in which you should test for are pH, disinfection (e.g. chlorine, bromine) and total dissolved solids (TDS). Whilst these tests are the minimum, further parameters should be included in your testing regime to ensure effective water quality monitoring:

What are the acceptable levels for each spa water quality test?

In Table 1 we have summarised the key testing parameters, including the target range which you should be achieving for each test parameter. These are based on industry guidelines, but we would always recommend you check your local regulations to ensure full compliance.

Parameter Description Target Range
Bromine Very favourable in spa disinfection as it is more effective at higher temperatures. 4.0 – 6.0 mg/L
Free Chlorine Free chlorine is a measure of the most active disinfectant. 3.0 – 5.0 mg/L
Combined Chlorine Measure of chlorine that has been used up during the disinfection process. 0 – 1.0 mg/L
pH The measure of how acidic or alkaline the water is, this influences efficiency of the disinfectant. 7.0 – 7.6 pH units
Total Dissolved Solids Measure of dissolved organic and inorganic substances in the water. No more than 1,000 mg/L
Total Alkalinity Alkalinity protects the water from changes in pH. 80 – 200 mg/L CaCO3
Cyanuric Acid Protects chlorine ions from degradation by UV light. This may be used for outdoor spas. Below 200 mg/L
Calcium Hardness Measure of whether the water is scaling or corrosive. 80 – 200 mg/L
Ozone Some spas will have ozone generators, which provides a secondary disinfection and effectively kills infectious diseases and means you can have lower levels of disinfectant. 1.2 – 1.5 mg/L O3
Phosphate Naturally present in water and is a key nutrient for algae growth. Below 0.01 mg/L
Turbidity Measure of how cloudy the water is. This can indicate key problems in filter media, poor water chemistry and other issues in spa maintenance. Below 0.5 NTU

Microbiological testing for spas and hot tubs

In addition to the key testing parameters already outlined, it is recommended you do a full screen of microbiological contaminants through an accredited water testing laboratory. Performed on a monthly basis, the following tests should be completed:

  • Aerobic colony count
  • Coliforms
  • e.coli
  • P Aeruginosa
  • Legionella (recommended every quarter)

To get the most accurate picture of your microbiological contaminants, the sample should be taken when the spa is at its maximise usage, or immediately afterwards.

Hot tub and spa testing equipment

There is a wide range of testing methods to monitor your water quality and the required solution is dependent on the use of the spa facility. For domestic use, where the use of the spa is sporadic and limited to a small number of users, a basic test kit could be used. For commercial settings where the spa facilities are used by multiple individuals, a digital test solution is required. A digital solution will provide you with the most accurate results for the critical water quality parameters, giving a much clearer picture of your overall water quality.

To comply with HSG 282 guidelines, a photometer can be used for disinfection and pH monitoring, with an electrochemical sensor used for TDS monitoring.

Palintest’s Lumiso Pooltest 4 photometer has been specifically designed for testing spas and indoor pools, covering the key water quality parameters; Total & Free Chlorine, Bromine, pH and Total Alkalinity. This should be used in conjunction with our electrochemical TDS meter, for TDS and temperature measurement, giving you complete compliance to HSG 282.

For more information around our Palintest offerings for your spa maintenance, contact our team.

Health and safety guidelines for effective management of hot tubs and spas

To ensure that you are operating your hot tub or spa in a safe manner, you should consider the following guidelines:

  • Always ensure that bather numbers do not exceed the number of seats or stated bather load outlined in the manual.
  • In commercial settings such as holiday lets, the hot tub should be completely drained, cleaned, refilled and disinfected weekly or after each rental.
  • When refilling a hot tub, hypochlorite should be added to keep the chlorine residual at 5.0 mg/L. Please note, dosage of hypochlorite may be significant.
  • Cartridge filters should be cleaned regularly and monitored to ensure that the filter is operating properly; replacing when necessary.
  • During commissioning the hot tub or spa should be shock dosed with chlorine at 50 mg/L for 1 hour, with pH maintained between 7.0 – 7.4, before being fully drained. This also applies when a hot tub has been left empty and unused.

Whilst not a requirement, it is suggested that all spa facilities, including those for personal use, follow the guidelines of HSG 282 to ensure safe bathing.


For more information about spa testing, download our spa chemistry guide, containing all the information you need for effective management of spa facilities.


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