Understanding swimming pool water quality parameters

Understanding and effectively managing swimming pool water quality parameters can help keep your customers safe and your equipment functioning longer. It can create a more appealing facility and potentially save you thousands of pounds every year. 

Swimming pool water quality management is an art and science. Achieving exactly the right level of disinfection, while managing effective backwash and replacement activities is a delicate balancing act. It entails deploying the right resource when required and exercising informed judgement around implementing efficiencies. The right testing regime will give you the data you need to make these critical decisions in the most effective way.

What are the regulations for swimming pool water quality maintenance and testing?

It should be noted there are no swimming and spa-pool specific health and safety laws in the UK. However, pool and spa operators must comply with their general duties under the H & S at Work Act 1974 and associated regulations. 

For UK operators, the Pool Water Treatment Advisory Group (PWTAG) standards are regarded as best practice (also exhaustively documented in their Swimming Pool Water Book) - while HSG 282 is the main guidance document surrounding spa pool water testing.

Why monitoring and testing is important

Both swimming pools and spa pools (such as hot tubs and whirlpool spas) represent unique operational and health risks. They can easily be contaminated by sweat, urine, faeces, hair and skin - and become places where dangerous microbes - including Legionella bacteria - flourish.

What are the specific operator and pool manager responsibilities around microbiological sampling?

Although the risk of serious infection from pools is low in the UK, the PWTAG still say there are an average of 15 outbreaks in the UK annually. 

Operators are required to analyse water from their pools each month for E. coli and coliforms, Pseudomonas aeruginosa, and Aerobic Colony Counts.  For Spa Pools, where warmer temperatures increase the risks of certain bacteria, tests for Legionella should also be conducted once a quarter or as defined by the risk assesment.  However, considerations around Legionella should form part of the risk assessment for all pools - and testing carried out if deemed necessary.

The guidance says pool managers should ensure that microbiological samples are:

• Taken at appropriate intervals
• Results recorded in the pool log book along with chemical analysis results
• Remedial actions and follow up samples taken following an adverse report

Microbiological tests should be:

• Performed by trained and competent personnel to prevent sample contamination
• Microbiological analysis should be carried out in a laboratory accredited for the analysis to ISO17025 standards

Adverse indications

The aerobic colony count (ACC) after 24 hours incubation at 37°C will show the overall microbiological quality of the pool. The continued presence of coliforms and especially E. coli is likely to indicate the presence of serious contamination arising as a result of a breakdown in the treatment system. 

The presence of the potential pathogen P. aeruginosa could also indicate treatment failure with likely colonisation and biofilm formation on the pool filter and elsewhere. 

If there are health problems associated with the use of the swimming pool, it may be necessary to test for other organisms, including:

• Staphylococcus aureus,
• Cryptosporidium, 
• Giardia

In these circumstances advice should first be sought from the local Health Protection Unit and a microbiologist.

Chemical testing requirements

Chemical tests should also be performed, preferably on site, at the same time as sample collection for microbiological tests. Results should be recorded in the log book and note:

• pH value and the concentration of free and total disinfectant in the pool water
• Maintenance records and bather numbers for the pool 
• Information on any mechanical failures 
• Water appearance

Clearly, any adverse results from these tests may require the pool to be closed or its use restricted whilst the problems are resolved.

When a more regular regime is required

Microbiological sampling should also be done daily or at least weekly:

• When a swimming pool is first used or recommissioned
• After a report of ill-health following pool use
• If there are problems or contamination incidents

7 benefits of swimming pool water testing

Effective swimming pool water testing is vital not just because it protects users from possibly lethal infection, but it can indicate underlying maintenance issues and prevent damaging overdosing.  

Active management prevents dirt build-up, destroys hazardous microbes and renders organic matter inactive. And there’s much that a regular testing regime can tell you about how to prioritise and optimise these processes for the most cost-effective management of your swimming pool.

An effective swimming pool water testing regime - including chemical analysis and microbial testing - can indicate:

1. Whether replacement and backwashing are being undertaken appropriately. With rising water and disposal costs you need to be certain these activities are being performed at the right time and with the right results. 
2. If disinfection levels are adequate. Appropriate dosing is vital if you are going to control the growth of dangerous bacteria and keep the pool water clear and hygienic for users
3. If there has been unnecessary or excessive chemical dosing. Not only can this excessive dosing pose a potential health risk to pool users, it can damage equipment and pool finishes
4. If the water treatment plant is coping effectively with the bather load
5. The condition of the filter bed and if any maintenance needs to be done
6. Crucial intelligence about pool quality, general hygiene levels and the bathing experience
7. If the plant is under strain or likely fail in the near future