TreeFiter said:
chem geek, what I meant by trichlor tablets being an industry standard is that if you pick a pool at random, it probably uses trichlor tabs. You can't just go to Walmart and pick up most of the other options for chlorine. Yes you can buy bleach, but if your average pool owner was doing that instead of using trichlor tabs, there wouldn't be a whole section of the store devoted to pool products. I don't doubt that TFP is helping a significant number of pool owners, and that these methods are catching on, but you can't deny that trichlor tablets are a very significant source of chlorination. Thats not to say its without problems as you and others have demonstrated.
For almost ten years I was able to manage pools using only trichlor without many problems. Knowing what I know now, I suspect that regional climate plays a pretty big part in this. If every few weeks a pool gains a few inches of water from rain, there is constant dilution and CYA is managed without the need for me to do anything extra. In a more arid climate, I would imagine problems with CYA tend to be more significant.
It does vary in different areas of the country. As the previous post by chiefwej shows, short swim seasons, smaller pools, summer rains with overflow (not evaporation), winter rains or partial drain for winterizing, and backwashing sand filters can all keep CYA in check especially in combination. Also, some fill water is low in phosphates and if they aren't added to a pool then algae growth can be lower as a result.
As an opposite example was my own pool 10 years ago. I have a 16,000 gallon pool, an oversized cartridge filter (4-cart, 340 square foot total) that only needs cleaning once a year, dry summers with no rain, an electric safety cover where I used a pool cover pump over the winter so no winter rain overflow. The pool wasn't used quite as much as it is now so I only had 0.7 ppm FC per day chlorine usage where I maintained 3 ppm FC using Trichlor pucks in a floating dispenser. I also used lots of "extras" including an algaecide (mix of Polyquat and linear quat) but only every other week, clarifier, enzyme, and metal sequestrant since all of it was free since I knew someone who worked at a pool chemical manufacturer. My fill water has 400 ppb phosphates. The first year was fine, but in the middle of the second year I couldn't keep up with chlorine demand so I added more pucks to the dispenser and then to the skimmer and the pool started to look dull and then cloudy. It was the start of an algae bloom though I didn't know it at the time. My CYA had started out at 30 ppm, but after 10-11 months of Trichlor use it had increased to 150 ppm when the problems occurred.
That's when I found The PoolForum and Ben Powell's chlorine/CYA chart and decided to pull out my old chemistry books and learn pool water chemistry. I've never looked back.
Trichlor is very popular, but problems with algae in pools are also very common. However, it's a statistical thing given the circumstances so while a portion of the pools using Trichlor and not using mitigating methods (algaecides, phosphate removers) may have a problem, some pools have no problems at all for years, others have problems every few years, while some have problems every year. Pool stores and chemical manufacturers make more margin on algaecides, phosphate removers, clarifiers, flocculants, enzymes and other specialty chemical products.
As for pool store sales, the one in my area sells both Trichlor and chlorinating liquid -- lots of both. Again, this varies by area. [EDIT]
This thread is just the most recent example of someone getting "chlorine lock" every year (which of course is not really "lock" but too low an FC for a high CYA), presumably now towards the latter part of their swim season. We usually see most problem pools with algae in August and beyond since the CYA has built up over several months (and the FC not raised proportionately). Again, there are those with problems every year, some with problems every few years or this is the first year they've had problems, and others that never have a problem. The pool industry uses this fact to pretend that there's voodoo going on that cannot be explained and that it most certainly proves that "CYA doesn't matter" but we know that isn't true. They use the argument that "real pools" are different than laboratory chemistry as if somehow real pools are a parallel universe where the laws of physics and chemistry do not apply. It's insulting and ultimately deceitful. [END-EDIT]
