Circulation, Coffee, and Tea

I live in the south and we drink ice tea and eat at cracker barrel. It's just a way of life. As well, I like my ice tea and coffee sweetened...just never developed the taste for black coffee, but sometimes take it with cream.What does this have to do with circulation? The coffee and tea Police. These are unscrupulous servers walking around with a pot of java or pitcher of tea, just waiting to pounce on your cup. You see, its easy to get the right amount of cream and sweetener in the coffee, but if they catch you half cup, while you are not just can never get it right again. Just can never guess, or may not remember just where that glass was when they sprung a "warmer" or see, its a problem of dilution.One thing finally occurred to me by reading some of the historic work of Stephen DeM. Gage. You may not know him, but most of the standard practices of the pool industry owe their origination to his work. From very early 1900s to about 1928, Mr. Gage was THE defining person on circulation, sanitization, and filtration What I can say unequivocally is nothing he wrote then was incorrect and there is no doubt that Health Departments and Trade Organizations lifted his work, and the work of the American Public Health Association, and then changed it, or simplified it, to the point that it was no longer correct.Which brings us back to Dilution and some of Mr. Gage (and Bidwell's) Best work: water circulation and turnover. When we talk about 6, 8 and 12 hour turns, it all falls back on the statistical work of Gage and Bidwell. What is exciting is if we take suction COMPLETELY out of the discussion, it's far easier to understand how our pools are cleaned and sanitized and the key is sequential dilution.

gage - father of pool circulation

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?
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  • I am the same type of coffee drinker. Lot's of cream and plenty of sugar. You have to be quick with your hand to cover your cup and tell them not to mess with the mix. That usually works.
  • Great post, well stated.
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