(Created page with "=Turnover of Pool Water= You will see its aid in the TFP Forums that turnover is a myth. What is meant by that shorthand saying is that there is no science behind the pool wa...") |
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=Turnover of Pool Water= | =Turnover of Pool Water= | ||
| − | You will see | + | You will see it said in the TFP Forums that turnover is a myth. What is meant by that shorthand saying is that there is no science behind the pool water needing any number of "turnovers" and that 100% water turnover is not achievable. |
Trying to achieve a turnover goal gets pool owners to focus on the wrong metrics when selecting a pump and then running the pump faster then necessary if it is a variable speed pump (VS). | Trying to achieve a turnover goal gets pool owners to focus on the wrong metrics when selecting a pump and then running the pump faster then necessary if it is a variable speed pump (VS). | ||
| − | There are times, such as during the | + | There are times, such as during the [https://www.troublefreepool.com/blog/2018/12/12/slam-shock-level-and-maintain/ SLAM Process] clearing algae, when you need maximum filtering and running your pump at high speeds 24/7 is recommended. For normal pool operation that is unnecessary and is further discussed in the Pool School [https://www.troublefreepool.com/blog/2019/01/18/determine-pump-run-time/ Determine Pump Run Time] article. |
You need to run your pump for a reason, and all we are saying is that "turnovers" are not a reason by itself. | You need to run your pump for a reason, and all we are saying is that "turnovers" are not a reason by itself. | ||
| − | If you have a SWCG, then you need to run the amount of time it takes to generate the amount of chlorine your pool needs. That is a real reason to run the pump. | + | ==Running the Pump to Achieve Turnovers is Unnecessary== |
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| + | If you have a SWCG, then you need to run the amount of time it takes to generate the amount of chlorine your pool needs. That is a real reason to run the pump. You might only have to run my pump 6 hours, because you have a large SWCG and a small pool, or you might have to run your pump for 18 hours, because you have a large pool with a small SWCG. The point being that we believe in running the pump to achieve some result, and not just to meet some magical number that someone pulled out of their rear. | ||
The main reasons to run your pump are: | The main reasons to run your pump are: | ||
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#To skim your pool. | #To skim your pool. | ||
#To mix chemicals if you manually add them. | #To mix chemicals if you manually add them. | ||
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| + | ==Turnover of 100% Cannot be Achieved== | ||
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| + | Pools have very poor hydraulic efficiency and so even when you run multiple turnovers, the pool equipment does not "See" all of the water. Even if you assumed "perfect" mixing of the pool water, you would see the following dilutions:<ref>https://www.troublefreepool.com/threads/1-hour-pool-turnover-and-moving-water-possible.50935/post-430457</ref><ref>http://consensus.fsu.edu/FBC/Pool-Efficiency/FAU-FPL-NSPI_1984_study-efficiency_of_circulation_systems.pdf</ref> | ||
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| + | *1 turnover: 63.2% | ||
| + | *2 turnovers: 86.5% | ||
| + | *3 turnovers: 95.0% | ||
| + | *4 turnovers: 98.2% | ||
| + | *5 turnovers: 99.3% | ||
| + | *6 turnovers: 99.75% | ||
| + | *7 turnovers: 99.91% | ||
| + | *8 turnovers: 99.966% | ||
| + | *9 turnovers: 99.988% | ||
| + | *10 turnovers: 99.995% | ||
| + | |||
| + | You never get to 100% and again, the above assumes perfect near instantaneous mixing in the bulk pool water. | ||
| + | |||
| + | Thus, in a theoretical pool with perfect mixing (so basically, no pool ever in existence), it takes 7 turnovers of the water to get the pool equipment to "see" 99.9% of the water. Therefore, any sanitizer that doesn't establish a residual concentration (ie, UV, Ozone) will be very ineffective at sanitizing. | ||
Revision as of 14:57, 23 June 2022
Turnover of Pool Water
You will see it said in the TFP Forums that turnover is a myth. What is meant by that shorthand saying is that there is no science behind the pool water needing any number of "turnovers" and that 100% water turnover is not achievable.
Trying to achieve a turnover goal gets pool owners to focus on the wrong metrics when selecting a pump and then running the pump faster then necessary if it is a variable speed pump (VS).
There are times, such as during the SLAM Process clearing algae, when you need maximum filtering and running your pump at high speeds 24/7 is recommended. For normal pool operation that is unnecessary and is further discussed in the Pool School Determine Pump Run Time article.
You need to run your pump for a reason, and all we are saying is that "turnovers" are not a reason by itself.
Running the Pump to Achieve Turnovers is Unnecessary
If you have a SWCG, then you need to run the amount of time it takes to generate the amount of chlorine your pool needs. That is a real reason to run the pump. You might only have to run my pump 6 hours, because you have a large SWCG and a small pool, or you might have to run your pump for 18 hours, because you have a large pool with a small SWCG. The point being that we believe in running the pump to achieve some result, and not just to meet some magical number that someone pulled out of their rear.
The main reasons to run your pump are:
- To generate chlorine if you have a SWCG or tab feeder.
- To skim your pool.
- To mix chemicals if you manually add them.
Turnover of 100% Cannot be Achieved
Pools have very poor hydraulic efficiency and so even when you run multiple turnovers, the pool equipment does not "See" all of the water. Even if you assumed "perfect" mixing of the pool water, you would see the following dilutions:[1][2]
- 1 turnover: 63.2%
- 2 turnovers: 86.5%
- 3 turnovers: 95.0%
- 4 turnovers: 98.2%
- 5 turnovers: 99.3%
- 6 turnovers: 99.75%
- 7 turnovers: 99.91%
- 8 turnovers: 99.966%
- 9 turnovers: 99.988%
- 10 turnovers: 99.995%
You never get to 100% and again, the above assumes perfect near instantaneous mixing in the bulk pool water.
Thus, in a theoretical pool with perfect mixing (so basically, no pool ever in existence), it takes 7 turnovers of the water to get the pool equipment to "see" 99.9% of the water. Therefore, any sanitizer that doesn't establish a residual concentration (ie, UV, Ozone) will be very ineffective at sanitizing.
