Hi Mike;
As Janet said, indoor pools are different than outdoor pools, and commercial pools are different than residential pools: indoor, commercial pools are REALLY different.
The good news is, I have some extensive experience with pools like yours. The bad news is, I have more experiential answers, than I do scientific ones. I found some things that seemed to work, but I can only guess why. If there is reliable info on what happens in a hot commercial indoor pool like yours, I haven't found it.
The problem is worse on hot pools, like yours, than on colder ones.
In general, the effects you describe are from chlorinated organics. In the potable water business, they are often called DBPs or Disinfection By-Products. You'll also seem them referred to as THMs -- Tri-Halo-Methanes, although that is a narrower term.
First, let me tell what I found does NOT work:
#1 - 'Shocking' or breakpoint chlorination.
If the organics were simple ammonia, that would work, but they are not. As a result, 'shocking' can actually make the problem worse.
#2 - Non-chlorine shocks
I found ZERO improvement, at any level of use. When I tested the, I was able to buy 'Oxone' cheaply in 50# (I think maybe they were 20Kg) bags, so I tested higher levels than recommended, as well as recommended levels. Using monopersulfate totally screws up ORP based control and DPD testing, but I found no improvement whatever in water quality.
#3 - Clarifiers
No effect, even though I was using a sand filter.
Second, there was one thing that I found absolutely and dramatically DID work: contaminant source control!
#1 - On one pool, I got a HUGE improvement by persuading the toddler-swim class teacher to shorten classes from 1 hour to 45 minutes, and require that moms put their toddlers on the potty before swimming, "whether they thought they had to go, or not". This step had the single greatest effect of anything I ever did!
#2 - Placing signs in the pool and women's locker room begging and pleading and threatening women to refrain from using lotion before entering the pool, and asking them to PLEASE wash it off, if they already had it on.
In general, you want to understand your contaminant sources:
+ USS competitive swimmers (ie, 2 hour practice swimmers) ALL pee in pools. I am NOT kidding or exaggerating about this. I absolutely do know. Anything to reduce this helps. Coaches hate it, but a mandatory hourly 'potty' break can work wonders. Of course, the coaches then have to chase all their slackers out of the bathroom after, so it becomes an ongoing effort to maintain the required break.
+ Babies and toddlers pee in pools, and babies poop in pools. Swim diapers do NOTHING to help with this. What makes a swim diaper is simply that they don't 'blow up' and clog the filter. There's nothing you can do about the babies, except keep them out of the pool. But the toddlers can be managed per above.
+ Older women in water aerobics may be the worst. (My wife was a water aerobics instructor for years, so I'm not guessing here.) They often wear too much lotion, too much perfume (it often lies in an absolutely choking layer 2" above the water*) and have leaky bladders (my wife would overhear them discussing their problems, in the locker room). A mandatory shower first policy + signs will help. With this population, they tend to be enforcers: (I had to do so, so you do too!). Explaining that THEIR discomfort results from their fellow swimmers body lotion or full bladder can work wonders, because they will say to each other what you can't.
+ Lowering water temperature will help too, because doing so reduced skin-drying effects AND sweating.
+ In general, encouraging showers helps a LOT because most people will pee when they shower, so you kills two birds with one stone, so to speak. Also, making sure NO class runs over 1 hours without a break helps.
+ But, you also need to OBSERVE your pool. There may be unexpected sources of contamination there, say a PT class that FOLLOWS a massage therapy session. In general, you are looking to reduce all of the following:
-- urine, feces, spit
-- sweat !
-- lotion, body oil, suntan lotion
-- hair conditioner
-- perfume
+ There is another class of problem contaminants I should mention, even though you indicated you did not use them:
-- algaecides
-- enzymes (see below)
-- defoamers
-- pH stabilizers (beside borax)
-- non-chlorine shocks (some can cause SEVERE problems!)
-- bromine tabs (hydantoin build up can cause serious problems, too)
-- hodge-podge pool chemicals -- use ONLY single ingredient products !!!! This is very important.
Third, there are some operational improvements that will help.
+ Improved aeration. (TO BE EXPANDED)
+ Improved ventilation (TO BE EXPANDED)
+ Lowered water temps (TO BE EXPANDED)
+ Chlorination consistency (TO BE EXPANDED)
+ Higher pH (TO BE EXPANDED)
+ Improved filtration (TO BE EXPANDED)
+ Enhanced filtration (TO BE EXPANDED => contaminant adsorption)
+ Improved operational stability (TO BE EXPANDED)
+ Regular water replacement plan (TO BE EXPANDED)
Finally, AFTER you've done everything above, it might be worthwhile to
+ test the use of enzymes (TO BE EXPANDED)
+ consider the use of UV irradiation (TO BE EXPANDED)
+ (last resort) adopt a European type ozonation / de-ozonation process with post chlorination
==> It's going to take awhile to finish this thread <==
Ben
* Funny story: one lady who frequented my wife's pool during the open swim period when my son and I (the one in this thread: Chattanooga Rat Race, minus about 18 years) apparently applied cheap perfume with lawn sprayer. Trying to swim laps, when she got in, choked me and triggered my son's asthma. But we worked out a solution. Like many of the women in her set, she did not want to get their hair wet . . . at ALL! So I'd have my son practice his butterfly stroke or do fast kick sets, every other lap. She got out, and complained to the manager -- with whom I'd already cleared my plan. (This lady was a complainer, and an irritant to other patrons as well.) The manager, struggling to keep a straight face, explained that it was an open swim period, and that the club really couldn't guarantee pool users would be able to keep their hair dry. She flounced off to the locker room in a manner possible only for overweight 65 year old women, hmphing all the way, as the staff collapsed into silent giggles.
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