Swimming Pool Turnover Explained

Swimming Pool Turnover

Swimming pool turnover is the time it takes for a volume of water equivalent to the swimming pool volume to make one pass through the system. It is calculated by dividing the volume by the flow rate.

It would be impossible to calculate the turnover time, without knowing the flow rate. Therefore, all pools should be fitted with a flow rate meter.

If the turnover time of a pool is too long, pollution levels will start to build up. If the turnover time is too short, the water will be travelling too fast through the system and this will have a negative impact on the effectiveness of the filtration system (slower filtration is usually better than faster filtration).

Flow Rate

To ensure your pool is properly disinfected and free of pollutants, it’s crucial to have excellent circulation hydraulics. That means every corner of the pool should be served with a steady flow of water, and without good hydraulics, your pool could be at risk.

The speed at which water flows through your pool’s circulation system is referred to as the flow rate, which is typically measured in cubic metres per hour (m3/hr). Sometimes, flow rate is expressed as gallons per minute (GPM) or litres per minute (LPM).

If you don’t know your pool’s flow rate, you won’t be able to determine its turnover time – the amount of time it takes for the pool volume to make one full pass through the circulation system. That’s why it’s essential to measure your pool’s flow rate accurately.

To measure flow rate, you’ll need a flow meter that’s regularly maintained and calibrated to ensure accurate readings. Knowing your pool volume is also important. You can calculate your pool volume by multiplying the length by the width by the average depth and expressing it in cubic metres (m3).

For instance, if your pool is 25m long, 12m wide, and has an average depth of 1.4m, its volume would be calculated as follows:

25m x 12m x 1.4m = 420m2

If the flow rate was indicated as being 150m3/hr (from the flow rate meter in the plant room), then the pool turnover would be calculated like this:

420m3 / 150m3/h = 2.8 hours

Recommended Turnover Rates

• Diving Pools 4 – 8 Hours
• Domestic Pools 4 – 8 Hours
• 50m Olympic Pools 3 – 4 Hours
• 25m General Use Pools 2.5 – 3 Hours
• Leisure Pools Over 1.5m Deep 2 – 2.5 Hours
• Leisure Pools 1 – 1.5m Deep 1 – 2 Hours
• Leisure Pools 0.5 – 1m Deep 0.5 – 1.25 Hours
• Leisure Pools Less Than 0.5m Deep 10 – 45 mins
• Hydrotherapy Pools 0.5 – 1.5 Hours
• Teaching Pools 0.5 – 1.5 Hours
• Waterside Splash Pools 0.5 – 1 Hour
• Interactive Water Features 20 mins
• Domestic Spas 15 mins
• Commercial Spas 6 mins
• Leisure Water Bubble Pools 5 – 20 mins