What is swimming pool water?
Swimming pool water is treated water specifically maintained for use in swimming pools. The same approach is used for water used in spas, hot tubs and hydrotherapy pools. Impurities introduced into the water from swimmers and the wider environment are managed through chemical and mechanical treatments to ensure the water remains clean, clear, and safe to use.
Treatments include the application of chemical disinfectants such as chlorine or bromine, pH balancers, algaecides, and stabilisers. Filtration and circulation equipment is also used to remove debris, while regular testing and maintenance ensure the water remains visually appealing, hygienic, safe, and comfortable for swimmers.
Why test swimming pool water?
Unlike other water systems found in homes and commercial premises where the water is flushed or drained away after each use, swimming pools, hot tubs and spas could be considered as a re-circulating water system where the water is retained and re-used many times over.
If you’re not testing the chemical and microbial water quality regularly, taking steps to maintain balance and keep it clean, issues such as pH and water clarity can change, and more worryingly bacteria can start to grow rapidly.

What bacteria can contaminate a pool, spa or hot tub?
Bacteria such as E. coli, Pseudomonas aeruginosa and Legionella thrive in warm, poorly or untreated water and have the potential to make people using the pool or spa very ill.
Don’t assume that water which appears crystal clear is clean and safe to use – the types of bacteria which can grow in water are invisible to the naked eye.
UK laws dealing with water quality testing in pools, spas and hot tubs
UK health and safety laws dealing with swimming pool and spa water quality, testing and treatment really only come into play if you’re running a business such as a leisure centre, gym or hotel, or the pool is in a holiday property which is let to paying guests.
Owners and operators of pools and spas need to ensure sure that the water quality and treatment programmes are effective and meet current standards. Although the law might not apply to domestic pools and spas, they provide excellent guidelines and standards which it makes sense to read, understand and comply with.
For more information both the Health and Safety Executive and the Pool Water Treatment Advisory Group (PWTAG) provide excellent guidance to help pool operators comply with health and safety law.
Microbial water testing for pools and hot tubs
It is very important that regular microbial analysis is carried out to ensure the effectiveness of the water treatment programme is maintained and the pool is safe to use. Specialist microbial analysis is carried out in the laboratory, not in-field.
Swimming pool water testing
Swimming pools operated as part of a business should be tested on a monthly basis.
Microbial testing of privately operated pools is at the owner’s discretion, however we recommend the same testing frequency.
Our swimming pool microbial laboratory testing suite includes for the following: