A splash pad sprays water upward and outward, directly at the people standing on it. Most of those people are young children, who put their faces in the jets, swallow mouthfuls of water and breathe in the fine mist that hangs over the pad on a warm day. That combination, a breathable aerosol delivered straight to a vulnerable audience, is exactly what makes interactive water features a water-safety concern rather than just a maintenance task. Whether your feature runs fresh water to drain or recirculates it through a tank, it needs a deliberate, site-specific regime covering both Legionella and Pseudomonas.
This article is general information for operators and duty holders, not medical advice. For symptoms or health concerns, direct people to the NHS guidance on Legionnaires’ disease [7]or to a clinician.
Two designs, two risk profiles
Interactive water features generally fall into one of two designs, and knowing which you have is the foundation of everything else.
A run-to-waste (or “potable feed”) system draws fresh mains water, sprays it once and sends it to drain. There is no storage and no recycling, so the water arriving at the jets is as good as your incoming supply, provided pipework does not let it warm up or stagnate between bursts of use.
A recirculating system collects sprayed water in a balance tank or reservoir, treats it and pumps it back to the nozzles. This is more efficient with water but carries a higher infection risk: the same body of water is reused, it warms in sun and in plant rooms, it picks up dirt, sun cream, leaves and faecal contamination from bathers, and it offers the warm, nutrient-rich conditions that waterborne organisms favour. HSE treats aerosol-generating water features as “other risk systems” that require identification and control under the same risk-based approach as cooling towers and spa pools [1].
Both designs aerosolise water at users. The design tells you how hard you have to work to keep that water safe.
The dual concern: Legionella and Pseudomonas
Two organisms dominate the assessment, and they behave differently.
Legionella is an inhalation risk. The bacteria multiply in warm water and infect people who breathe in contaminated aerosol, which is precisely what a spray pad produces. Splash pads and interactive fountains have been linked to waterborne infection in published outbreak and surveillance literature, and recreational water features that aerosolise water are recognised as a credible source [1][2][3].
Pseudomonas aeruginosa and other waterborne organisms are more a feature of recirculated, warm, sunlit water and of skin, eye and ear contact during play. Where water is reused and bathers are immersed in spray, the recreational-water concern broadens beyond Legionella alone [2][3]. For background on this organism and where it thrives, see our guide to Pseudomonas aeruginosa in water systems.
The practical conclusion is that an interactive feature with recirculation should typically be managed much like a pool or spa, with continuous disinfection and monitoring, while even a run-to-waste feature needs controls against stagnation and warming.
Practical checklist for operators
Use the following as a starting framework. It does not replace a competent, site-specific risk assessment, which is the legal and practical anchor for everything below [1][9][10].
- Know your design. Confirm in writing whether the feature is run-to-waste or recirculating, and map every tank, pipe, pump, filter and nozzle. You cannot control a system you have not drawn.
- Maintain a disinfectant residual where recirculating. Treat recirculating features as recreational water: hold a continuous, measured disinfectant residual (commonly chlorine or bromine based) within the range your treatment regime specifies, and keep the water balanced so the disinfectant works [2].
- Run adequate turnover, filtration and UV. Size circulation so the whole water volume passes through filtration frequently, and consider supplementary UV. The aim is to remove the bather-introduced soiling that feeds microbial growth [2].
- Control temperature. Warm water accelerates growth of Legionella and Pseudomonas. Limit how much the balance tank and exposed pipework heat up in sun and in plant spaces, and treat warm water as a trigger for closer monitoring [1][2].
- Clean and manage the balance tank. Schedule routine cleaning, disinfection and inspection of tanks, gullies, drains and nozzles. Remove debris, biofilm and any standing sediment, because biofilm shelters organisms from disinfectant.
- Flush after downtime. Features are seasonal and often sit idle overnight, between events or over winter. Stagnant water is a primary growth opportunity, so flush thoroughly and, for recirculating systems, re-establish treatment before reopening. Our guidance on Legionella in misting systems and humidifiers explains why intermittently used aerosol equipment deserves particular attention.
- Monitor and keep records. Log disinfectant residuals, pH, temperatures, turnover and cleaning, and arrange microbiological sampling appropriate to the design (Legionella and, for recirculating features, Pseudomonas and general indicators). Records demonstrate control and reveal drift before it becomes a hazard.
- Site away from intakes and dwell points. Position features so aerosol does not drift into building air intakes, windows, seating or queues, and so prevailing wind does not concentrate mist over crowds [1].
- Define competence and response. Name who runs the daily checks, who interprets results and what happens, including closing the feature, when a parameter goes out of range.
A pool-grade mindset, applied to play
The mental model that serves operators best is to treat a recirculating interactive feature with the same seriousness as a hot tub. The principles of continuous disinfection, controlled water balance, turnover and disciplined record keeping that govern spa pools transfer directly, and the consequences of neglect are comparable. Our article on the safe operation of spa pools and hot tubs under HSG282 is a useful companion, because much of that discipline applies wherever warm, recirculated water is sprayed at people.
Run-to-waste features demand a lighter but still deliberate regime focused on preventing the supply from warming or stagnating, and on keeping nozzles and surfaces clean. In both cases, the regime should be written down, owned by a named competent person and reviewed whenever the system, its use or its surroundings change.
Frequently asked questions
Are splash pads a Legionella risk if the water goes to drain?
A run-to-waste feature lowers the risk because water is not reused, but it does not remove it. The system still creates a breathable aerosol, and water can warm and stagnate in pipework between bursts of use, which is where Legionella can grow [1]. A competent assessment should still cover stagnation, temperature and cleaning, even for potable-fed features.
Is Pseudomonas a bigger concern than Legionella on a splash pad?
It depends on the design and how people use it. On recirculating features with warm, reused water and close skin, eye and ear contact, Pseudomonas and other recreational-water organisms can be a leading concern alongside Legionella [2][3]. The safest approach is to assess for both rather than assume one matters more, and to control the warm, soiled water that favours either.
Who is responsible for a shopping-centre or park water feature?
Responsibility sits with the duty holder for the premises or the system, typically the employer, owner or operator who controls it. Their general duties to assess and control health risks arise under health-and-safety and substances legislation, with HSE guidance setting out how to do it for water systems [1][9][10]. Where management is shared or contracted out, the assessment should record exactly who does what.
What is the single most important control for an interactive water feature?
There is no single control, but the closest is a competent, site-specific risk assessment that drives a written scheme, because it determines which controls you need and how to run them [1]. For recirculating features in particular, maintaining a continuous, monitored disinfectant residual in balanced water is commonly the most decisive day-to-day measure [2].
Sources
- HSE, HSG274 Part 3 (2024), What are other risk systems and risk identification and control, p.101 to 102. https://www.hse.gov.uk/pubns/books/hsg274.htm
- HSE, HSG282, treatment and monitoring expectations for interactive and recirculating water features. https://www.hse.gov.uk/pubns/books/hsg282.htm
- UKHSA and published outbreak literature, evidence that splash pads and interactive fountains have been linked to waterborne infection (as cited in recreational-water guidance). https://www.cdc.gov/legionella/about/index.html
- NHS, Legionnaires’ disease, conditions overview. https://www.nhs.uk/conditions/legionnaires-disease/
- HSE, Control of Substances Hazardous to Health Regulations 2002 (COSHH), as applied to Legionella. https://www.legislation.gov.uk/uksi/2002/2677/contents/made
- HSE, Health and Safety at Work etc. Act 1974, general duties. https://www.legislation.gov.uk/ukpga/1974/37/contents