Guidance: How to complete a swimming pool dye test

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A dye test is a recognised method of assessing the effectiveness of pool water distribution. It shows the performance of the pool water circulation system under design conditions and enables an operator to make adjustments to the inlet system to achieve the desired result.

Guidance available on completing a dye test

• EN 15288-1:2018. Swimming pools for public use. Part 1 Safety requirements for design. 
• EN 15288-2:2018. Swimming pools for public use. Part 2 Safety requirements for operation. 
• HSG179. 2018. Health and safety in swimming pools. 4th edition. 
• PWTAG. 2017. Swimming pool water [hardcopy]. 3rd edition. 

Use cases for a dye test

Potential use cases for a dye test include: 

• A commissioning test in new-build pools before they are handed over for operation. 
• To assess the adequacy of any remedial changes which impact pool water distribution.  
• To investigate a suspected pool water distribution problem affecting water quality. 
• To identify the source of a leak. 

Dyes permitted for use in a dye test

EN 15288-1 set out at A.2 the dye chemicals which can be used in a dye test: 

• Uranin - dosed ideally at 0.3 g/m³ of pool water. 
• E123 - dosed at 0.1-0.15 g/m³
• E133 - dosed at 0.1-0.15 g/m³
• Eriochrome Black T - dosed at 0.2 g/m³ 

The quantity of dye to be used shall be calculated prior to the test and shall equal the pool water volume plus 60% of the usable volume in the balance tanks. 

How to complete a dye test

1. All persons completing a dye test shall be competent in achieving the outcomes of the test procedure set out in EN 15288-1:2018. 
2. Ensure all pool users have left the pool and access/egress points have been secured (EN 15288-1:2018, A.1). Notify other members of staff that a dye test is about to be performed. 
3. The system should be set to operate at normal filtration flow and the lowest permitted volume flow (as specified by the manufacturer). 
4. De-chlorinate the pool water and bypass any ozone or carbon treatment filters. 
5. Inject the dye into the circulation system via an appropriate dosing pump and injector at a continuous flow and uniform rate over the test period. 
6. The faster the pool water becomes evenly coloured, the more effective the pool circulatory system is. The test period is 15 minutes. An even distribution of the dye within 15 minutes, with a total uncoloured area of less than 2% of the pool volume, is satisfactory,
7. Photographic evidence or video recording of the results shall be made. 
8. The time taken from the first appearance of the dye in the pool tank to complete water colouring shall be recorded in a technical report (EN 15288-1:2018, A.6). A full history of dye tests undertaken at the site since commissioning should be retained at the site (EN 15288-2, cl.7.7.5). 
9. Once the test is complete, remove the dye from the pool water by re-chlorinating the swimming pool. The duration of re-chlorination should be broadly equal to the dye distribution duration.  

Citation. Jacklin, D. 2022. Guidance on completing a dye test. Water Incident Research Hub, 3 September.