Stephen DeM. Gage - He just looks smartHere is how it works. Start with a dirty pool and turn on the filtration equipment. Dirty water exits, and clean, sanitized water returns. No arguments there? Now, the clean water mixes with, or better dilutes, the dirty water and the pool becomes a "tad" more clean. Remember the coffee and tea police? This process continues until eventually, all of the dirt has been remove that was suspended in the water. What settles on the bottom, is removed by vacuuming or in-floor...or brushed to the "drain."That is how it works, and here are the numbers they came up with nearly 100 years ago. They expressed the volume of water entering the pool in terms of the "volume" of the pool and called it turnover rate or "T." So when the amount of water in 24 hours was equal to the volume of the pool, T = 1. If it was twice the volume, T = 2 and so on.What they demonstrated experimentally and mathematically is that it takes 7 turnovers to remove 99.9% of the dirt present. The numbers for pool purification look like this:T = 1 - 63% removedT = 2 - 86%T = 3 - 95%T = 4 - 98%T = 5 - 99.3%T = 6 - 99.7%T = 7 - 99.9%what is interesting is to go from 99.9% to 99.99% (0.09%) requires TEN turnovers! That last...almost .1% requires three more turnovers. Of course, all of this assumes no more dirt was added to the pool - not likely, those dirty people just won't stay out. They went on to model dirt coming into the pool and how many days it took for the system to "catch up" with the increasing load.Their conclusion by 1920?The recirculation system should be designed for a minimum of 2 turnovers and for heavy bather load, 3 or more. They suggested:" It is evident that the recirculation system should be kept in operation continuously and that the filters should be operated in the most efficient manner. If the Filters have an efficiency of only 50%, or the recirculation system is operated only half of the time, the effect will be the same as though the recirculation system were only half the size."that sums it up. Water is cleaned through sequential dilution and sanitization. Nothing is happening when the filter is off or the pool is stagnant. Doesn't matter where you take it from, so long as you put it back throughout the pool.I think the best part of the entire committee work was the slogan of the day:
Wouldn't it be great to say this today?