Hydrotherapy pool water safety is not an issue to be ignored as such facilities can present increased risks to patients, staff and others, especially if the water used in them is not managed and maintained correctly.
In this expert guide the water safety specialists at Water Treatment Services review the use and management of hydrotherapy facilities and what issues owners, managers and operators need to be consider to ensure optimum water quality and safety are maintained.
In the guide we consider the responsibilities around the control of legionella and Legionnaires’ disease, managing microbiological contamination, the requirements for hydrotherapy pool water testing, maintaining safe water temperatures, general water quality issues and good pool hygiene practices.
We have also included a number of useful tables that summarise what pool water quality tests are required, recommended testing frequencies, interpretation of the results, and specific action levels for both chemical and microbiological parameters.
Hydrotherapy pool water safety
If you own, manage or are responsible for a hydrotherapy pool special care should be taken to keep the water used in the pool clean and safe, given that this type of facility is often used by people with underlying medical conditions making them more susceptible to illness and infection.
Hydrotherapy pools are now commonplace in many large hospital physiotherapy departments, rehabilitation facilities and some care homes.
They also have role to play in many other types of complementary therapies for both humans and animals.
If you own, manage or are responsible for this type of pool there are a number of key points to bear in mind which will help to keep staff and patients safe, reducing the risk of illness and infection resulting from poor pool hygiene.
As the use of hydrotherapy pools grows across the world, ongoing research is helping to establish the best ways of using the warmth of the water to help improve health, recovery and well-being.
Academic papers on the topic are published in both medical journals, and Aquatics journals.
What is hydrotherapy?
Hydrotherapy is a therapeutic treatment involving water at various temperatures and pressures designed to provoke a response from the human body. It typically involves the use of standard swimming pools, hot tubs, spa pools or specially constructed physiotherapy tanks.
These sorts of pools are often found in hospitals, rehabilitation centres, care homes and residential facilities, whether funded publicly or by charitable donations.
What is aquatic therapy?
Aquatic therapy takes a slightly different approach, although still involves the use of water.
Aquatic therapy is more about using the resistance caused by being immersed in water to rehabilitate patients after an operation, illness or accident.
It can be used as part of an athlete’s training programme as exercising in water can reduce the risk of injury.
It can also be used in veterinary applications for the rehabilitation of animals recovering from operations or injury. For these types of therapy, it’s essential that the pool water is of an appropriate quality before patients and staff are allowed to use it.
Managing hydrotherapy pool safety
Typical water temperatures used in hydrotherapy pools are higher than those recommended for swimming pools and this can create more favourable conditions for the growth and proliferation of several waterborne pathogens.
These can include Legionella bacteria, E .coli, Pseudomonas aeruginosa, Coliforms, Mycobacterium avium and Mycobacterium species, along with less common infections such as amoebal, parasitic and other gastrointestinal infections, furunculosis (caused by Staphylococcus aureus) and Molluscum contagiosum (a viral skin infection producing papillomas).
Whatever the reason for having a hydrotherapy pool, there are a number of important issues that need to be considered that will help pool owners, managers and operators manage the risks associated with them to keep staff and patients safe, and comply with the law.
Managing the risks from Legionella bacteria and Legionnaires’ disease
Legionnaires’ disease is a rare but serious infection of the lungs. Most people who contract the disease eventually recover, although it can be very serious for people who are already ill or have a compromised immune system.
Legionnaires’ disease is caused by Legionella bacteria and is caught by inhaling fine droplets of water that have been contaminated with Legionella bacteria.
a water safety risk assessment is an essential management process for all hydrotherapy pools
The UK’s Health and Safety Executive’s Approved Code of Practice (ACOP) L8 deals with the control of Legionella bacteria and Legionnaires’ disease and makes for essential reading for those responsible for the operation of hydrotherapy pools.
The HSE’s ACOP L8 has a special legal status and requires owners, managers and operators of hydrotherapy pools to manage the risks associated with them.
This includes appointing a Duty Holder and competent Responsible Person to manage the risks, carrying out a detailed water safety or legionella risk assessment, implementing suitable control measures to manage the identified risks, regular testing to ensure the control measures are effective and maintaining records of tests and any actions taken.
Other essential guidance documents include the following:
- Health & Safety Executive HSG282 – The control of legionella and other infectious agents in spa-pool systems
- Health & Safety Executive HSG274 – The control of legionella bacteria in water systems
- Department of Health & Social Care HTM 04-01 – Safe water in healthcare premises
Microbiological testing of hydrotherapy pool water
If your hydrotherapy pool water becomes contaminated by waterborne pathogens including bacteria and other microorganisms, this can make people using the pool ill.
Bacteria can enter the pool in different ways including from the source or fill water, bathers, organic materials, through pool filters or sometimes because of faults in the mechanical components of the pool.
There is lots of advice available explaining how you can monitor your pool water for microbial quality including information from the water quality experts at Water Treatment Services. However, your risk assessment should give more detailed recommendations regarding the type and frequency of any water testing and these recommendations should be followed.
Unless your risk assessment recommends otherwise you should carry out the following microbiological tests weekly or when the pool is first used or recommissioned, following ill-health associated with the pool, if there are problems of contamination, or changes to the water treatment or general maintenance programme.
Further testing after reports of illness may also be needed for other organisms such as Cryptosporidium, Staphylococcus aureus, Giardia and possible viruses.
It is recommended that weekly water sampling should be carried out when the pool is in use, ideally when it is heavily loaded or immediately afterwards.
The best place to take samples is at the deep end, away from any inlets. It is also worth noting that leisure pools often have complex water flows to different areas and these may need more than a single sample.
You will need to arrange to have the water in the pool tested on a regular basis to make sure that it is safe.
The industry standard is that hydrotherapy pools are tested more frequently than swimming pools, given that the people using them are often more prone to infection than other members of the public. The UK’s Pool Water Treatment Advisory Group (PWTAG) recommends weekly microbiological tests.
As well as routine testing, you should also be testing hydrotherapy pool water after setting it up before it gets its first use, and before it goes back into use after it has been out of service for repairs.
If you are unsure about the quality of the water or suspect it may have been contaminated, test again.
If you’ve changed the way you are treating the water, you should also increase the frequency of pool water testing to make sure the new regime is working effectively.
Only companies offering UKAS accredited testing facilities such as Water Treatment Services should be used to test hydrotherapy pool water for microbiology.
Samples should be taken from the pools deep end at a depth of between 200mm and 400mm, ideally when it is in use or immediately afterwards.
At the same time as you take the samples, measure the levels of disinfectant used as this will help the lab with their analysis.
The key parameters from the microbiology report are the levels of E .coli, Total Coliforms, the Aerobic Colony Count or ACC, and Legionella bacteria.
This ACC result is sometimes referred to as Total Viable Count (TVC) or just Colony Count. Figures might start to rise with more people using the pool, lower levels of chlorine (disinfectant) or issues with the effectiveness of your water treatment programme.
A marginal failure of your microbiology tests means you should retest the water to confirm the first result.
If the microbiology report shows coliform bacteria in the pool water, then this shows that there are problems with faecal contamination or bad hygiene. Levels of up to 10 colony forming units (CFU) in 100ml of water means that the tests should be repeated.
Testing for legionella
It is recommended that hydrotherapy pools are tested for the presence of Legionella bacteria more frequently given that the people using them are potentially more prone to infection than other members of the population.
In hospitals and healthcare environments the main concern is protecting susceptible patients, so any detection of legionella should be investigated and the pool systems re-sampled to help interpretation of the results.
If pool water testing shows legionella at more than 100 cfu per litre of water, then repeat the tests and review the legionella risk assessment and control measures in place. Any required remedial actions should be implemented without delay.
Disinfection of the system should be considered.
Should results for legionella exceed 1000 cfu per litre then immediate action to close the pool and exclude people from the area should be taken.
The pool should be shock dosed for a minimum one hour.
The pool should then be drained, cleaned and thoroughly disinfected.
The legionella risk assessment and control measures should be reviewed and remedial actions completed as required.
Once these works are complete the pool can be refilled and retested, with a programme of frequent testing implemented until you are confident that the issues have been resolved.
Testing for E .coli
If you identify E .coli in your pool water, then this is a clear indication that faecal material has entered the pool.
The contamination might have come from dirty skin, or from accidental introduction into the water.
If you find E .coli in the pool, then repeat the pool water testing procedures straight away.
E .coli can cause serious illness, and can’t be ignored.
Testing for Pseudomonas aeruginosa
Another problematic bacteria in hydrotherapy pools is Pseudomonas aeruginosa.
Higher levels of this bacteria can cause infections on the skin, in eyes and ears.
While healthy individuals generally have little to worry about, patients who are already ill, have open wounds or compromised immune systems may be at risk.
If testing of the pool water shows more than 10 cfu per 100ml of water, then repeat the tests.
Look at how the water is circulating around the pool, and how the disinfection and filtration is working to try to identify areas in the pool which would allow the bacteria to grow.
Watch out for the accumulation of biofilm (slime) on pool and equipment surfaces as this can encourage the growth and proliferation of bacteria.
Frequency of microbiological testing, interpreting results and recommended actions
|Aerobic colony count (or total viable count) @ 37°C||Weekly||Aerobic or total colony count >10 cfu/ml||If the colony count is >10 cfu/ml and is the only unsatisfactory microbiological result, and residual disinfectant and pH values are within recommended ranges, the water should be re-sampled and re-tested|
|Aerobic or total colony count >100 cfu/ml||Check treatment system and manual testing results records immediately|
|Implement any remedial action as required|
|Re-sample and retest|
|Coliforms and E coli||Weekly||Coliforms and E coli present >1 cfu/100 ml||Occasional positive samples may occur if the pool has been sampled immediately after a contamination event before the disinfection system had time to be effective. A repeat sample should be taken whenever coliforms have been detected|
|Coliforms ≤10 cfu/100 ml||A coliform count of up to10 cfu/100 ml is acceptable provided that the residual disinfectant and pH values are within recommended ranges, there are no E coli present and the aerobic colony count is <10 ml|
|Coliforms present on repeat test or if >10 cfu/100 ml at any time||Indicates that disinfectant regime is ineffective|
|Shock dose the spa pool with 50 mg/l free chlorine circulating for 1 hour or equivalent|
|Drain, clean and disinfect|
|Review control measures and water safety risk assessment|
|Carry out remedial actions identified|
|Refill, disinfect and adjust pH to recommended range; and retest next day and then at frequent intervals until satisfactory control is achieved|
|Pseudomonas aeruginosa||Weekly||P aeruginosa present 10–50 cfu/100 ml with or without raised coliform, E coli or colony count||Take a repeat sample for testing|
|Scrub walls of balance tank, if any, and cleanse the filter|
|Chlorinate to 10 mg/l free chlorine, circulate and flush|
|If repeat sample contains P aeruginosa the filtration and disinfection processes should be examined to determine where the organism has been multiplying|
|P aeruginosa present >50 cfu/100 ml with or without raised coliform, E coli or colony count||Close pool|
|Shock dose the pool and balance tank, if any, with 50 mg/l free chlorine circulating for 1 hour or equivalent and flush through|
|Drain, clean and disinfect|
|Review control measures and water safety risk assessment|
|Carry out remedial actions identified|
|Refill, disinfect and adjust pH to recommended range; retest next day and then at frequent intervals until satisfactory control is achieved.|
|Legionella||Weekly||<100 cfu/l||Under control but maintain control measures. In healthcare environments the primary concern is protecting susceptible patients, so any detection of legionella should be investigated and, if necessary, the pool re-sampled to aid interpretation of the results in line with the monitoring strategy and risk assessment.|
|>100 cfu/l and up to 1000 cfu/l||Re-sample and keep under review. In healthcare environments if the minority of samples are positive, the system should be resampled. If similar results are found again, a review of control measures and a risk assessment should be carried out to identify any remedial action necessary, OR if the majority of samples are positive, the system may be colonised, albeit at a low level. An immediate review of control measures and a risk assessment should be carried out to identify any other remedial action required. Disinfection of the pool systems should be considered.|
|Review control measures and legionella risk assessment|
|Carry out remedial actions identified as necessary|
|>1000 cfu/l||Immediate closure of pool and exclude public from pool area|
|Shut down pool|
|Shock dose the pool with 50 mg/l free chlorine circulating for 1 hour or equivalent|
|Drain, clean and disinfect|
|Review control measures and legionella risk assessment|
|Carry out remedial actions identified|
|Refill and retest next day and then at frequent intervals until satisfactory control is achieved.|
Information extracted from Health & Safety Executive HSG282 and Department of Health & Social Care HTM 04-01
* The recommended testing frequencies and actions given here are provided as a guide, however, your water safety risk assessment should give more detailed recommendations regarding the type and frequency of any water testing and actions, and these recommendations should be followed. You should also test when the pool is first used or recommissioned, following ill-health (additional parameters may need to be tested), if there are problems of contamination, or changes to the water treatment or general maintenance programme.
Disinfection of hydrotherapy pool water
Most hydrotherapy and spa pool owners use chlorine to disinfect their pool water although other pool disinfectants are becoming popular including bromine, chlorine dioxide, silver stabilised hydrogen peroxide, ozone and ultra-violet light.
Maintaining optimum disinfection levels can help to stop skin becoming irritated, or allow waterborne pathogens to proliferate and potentially get into open wounds.
Skin irritation, known as dermatitis, is often caused by additives in water coming into contact with organic compounds like sweat or skin.
If you operate a spa or hydrotherapy pool, you should be measuring the free chlorine levels at least three times a day (as a minimum).
The levels should be maintained between 1.5mg and 5.0mg per litre of water.
Measure total chlorine levels at the same time as free chlorine, and these should not exceed 10mg per litre while the pool is being used.
Maintaining optimum pH conditions
We use the pH scale to measure how alkaline or acid a liquid is, including pool water. pH is expressed on a scale from 1 to 14. pH 7 is considered neutral, acidic solutions are below 7, above 7 is considered alkaline.
If the pH of the pool water drops too low and it becomes acidic problems will occur.
Acidic water conditions can make bathers’ eyes sting, or irritate their skin.
It can also start to corrode the metal fittings within the pool. If on the other hand the water starts to become too alkaline, scale can start to form and pool water clarity can be affected.
The pH levels of pool water can also have a significant impact on how effective any disinfectants, including chlorine are.
If the pH level is too high, chlorine can become much less effective.
Keeping the pH level of the water under control makes sure all disinfectant chemicals that you are adding to the water are working at their best.
It is recommended that water pH should be measured before you start using the hydrotherapy pool in the morning, and then every two hours throughout the day, and again after the pool has closed in the evening.
The ideal pH level for a pool should be between 7.0 and 7.6.
Maintaining water balance
Operators should also measure for the levels of total dissolved solids (TDS) and cyanuric acid. TDS should be no more than 1000mg per litre.
If the level of dissolved solids gets too high, this can mean that the metal parts of the pool workings will start to rust more quickly.
Steps should also be taken to control the alkalinity and calcium hardness of the water.
If the calcium hardness levels of the water become too low, corrosive water conditions can occur.
If the calcium hardness is too high, scale can start to form. Scale reduces the effectiveness of the pool filter system, can encourage microbiological contamination, and can raise energy costs.
Maintaining good water balance is all about taking measurements for pH, alkalinity, hardness, total dissolved solids and other factors, and trying to keep these various factors balanced.
Testing for chemical parameters and recommended actions
|Test||Typical Range||Recommended Action|
|<7.0 or >7.6||Close pool and check the operation and calibration of acid/alkali dosing units. Recheck pH once any faults have been rectified. If pH is still out of limits, the pool will need to be emptied and refilled with mains water to reach the typical pH range and additional treatment may need to be added to achieve this pH|
|Disinfectant||Chlorine 3–5 mg/l OR Bromine 4–6 mg/l||None|
|Chlorine <1 mg/l or >10 mg/l OR Bromine <2 mg/l or >12 mg/l||Close the pool, apply corrective actions and retest|
|Chlorine 1–2 or 6–10 mg/l OR Bromine 2–3 or 7–12 mg/l||Check dosing units are operating correctly. High levels of disinfectant can be lowered by partial replacement of pool water, once the underlying fault has been rectified. Low levels of disinfectant can be increased by shock dosing of pool water, once the underlying fault has been rectified|
|Combined chlorine||0<1 mg/l||None|
|>1 mg/l||Review control measures. High levels can be lowered by partial replacement of pool water, once the underlying fault has been rectified|
|Total dissolved solids (TDS)||No more than 1000 mg/l higher than the incoming fill water||None|
|>1000 mg/l higher than the incoming fill water||Review control measures. Pool will need to be emptied and refilled to lower concentration|
Information extracted from Health & Safety Executive HSG282
The results obtained from routine water quality testing can help identify a number of issues that may require attention including:
- the frequency of pool water changes are sufficient
- back-washing is effective
- water disinfection is working
- water treatment plant is effective
- under or overdosing of water treatment chemicals is avoided
- pool filters are working correctly
The test results taken should be recorded in a log book along with any remedial actions taken.
Monitoring water temperatures
It’s essential to have a process for keeping accurate records of pool water temperatures.
Measurements should be taken twice every day and recorded in a log book.
The water temperature should be kept at a steady level between 35.5°C and 36°C. For safety reasons it should never be allowed to exceed 38°C.
for safety reasons, water temperatures should not exceed 38°C
There are many neurological conditions which prevent patients recognising changes in temperature, and they may not notice that the water is too hot.
There is another group of patients whose health could deteriorate further if they are exposed to too much heat.
This group includes people with heart or lung conditions.
Additionally, if the water temperature drops, this can exacerbate a range of conditions such as chilblains and Raynaud’s disease.
Maintaining good poolside hygiene
The areas surrounding the pool should not be ignored.
They should be cleaned each day using pool water.
Additionally, every week, clean the poolside areas using chlorine releasing tablets in accordance with the manufacturer’s instructions.
If dirt accumulates on the poolside, you should have a spillage policy which tells members of staff how to clean it up.
Yearly inspections are also recommended… it’s best to do this at a time when the pool is emptied for thorough cleaning and any maintenance.
Effective hydrotherapy pool maintenance
It’s vital to have a written schedule for testing and maintenance your hydrotherapy pool.
You will need to develop a routine for testing the pool water every day, and find an independent, accredited specialist such as Water Treatment Services to perform the appropriate microbiology tests.
Your water testing and inspection policy should record what actions you take together with the standard of the water at the start of the day and the number of patients who are treated in the water during each session.
Patients and staff shouldn’t be in the water for more than an hour, and it’s usually best to split sessions into three blocks of 15 minutes each with a break between to reduce the risk of pool soiling.
Work out how and where you are going to store your sampling kits, to keep them in a good state. Always use equipment in accordance with manufacturer’s instructions, and train staff fully.
Specialist water safety risk management and water testing solutions
Water Treatment Services offer a comprehensive range of water safety risk management, water quality testing and laboratory analysis solutions to support operators of hydrotherapy pools in maintaining safe water conditions, protecting people and achieving compliance with current regulations.
Our experts can provide advice and support to help you identify the most appropriate strategies for the on-going management of your hydrotherapy facilities water to meet your needs.
Contact Water Treatment Services to find out more about our laboratory water analysis services including microbiological testing, chemical and in-field sampling services.
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians, in-field specialists and consultants we can offer professional, cost effective water safety and analysis support solutions across the whole of the UK and internationally.
Contact us today to learn how our expert water testing solutions can help you keep your water safe.
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