Unstabilized chlorine tablets?

[aylad]

So, if that's what your saying, how/why does one use Trichlor?

Trichlor can be useful IF the user understands the effect it has on the water. Trichlor adds CYA, as chemgeek explained, and is very acidic, so it tends to drive pH downward. It is useful for folks to use on a short-term basis, like vacations, to keep the pool clear until their return, or at the beginning of the pool season, when the owner wants to raise the CYA levels in the water. I personally use it at times in my pool. I live in a very warm climate, and my pool gets full sun all day,. I intentionally run CYA levels at around 100 ppm in order to decrease my chlorine useage, and due to high evaporation rates and splashout due to a high bather load, I have to top off my pool very frequently with tap water that is a pH of 7.8. There are times that it is very hard to maintain my CYA levels where I want them without using trichlor, and it helps keep my pH down in the lower 7-ish range. So..it can be useful, in the right situations. People just tend to get themselves in trouble when they don't account for the result of a high CYA without a corresponding chlorine increase.

BTW, you should be able to reply with your mobile device just like you do with your computer--it's just that your replies are going into a moderator queue and can't be seen on the forum until one of us mods it in, and Lisa and I haven't been too good lately about checking in as often as we normally do. I'll try to do better.....

[chem geek]

Also, I wouldn't say never use one source over another since some Trichlor use can be OK if you have some water dilution. However, for sure, it can't be your primary source of chlorine. The Cal-Hypo will increase CH, but does so at a slower proportional rate so water dilution helps more in this case. Basically, with CYA you run into problem certainly at 100 ppm or more though even lower levels can be an issue but handled with a higher FC target (assuming your regs allow that).

So let's say you have 10% water dilution per month. That would be 5600 gallons per month or around 1300 gallons per week which is more than a usual backwash but is possible for intentional dilution for 186 bathers (at 7 gallons per bather as per APSP-11 and other standards) or around 27 bathers per day (think of this as bather-hours per day). The following would be the steady-state levels assuming 2.5 ppm FC per day where around 0.5 ppm FC of that is to handle the bather load (it's about 4 grams chlorine per bather) and 2 ppm FC loss from sunlight and overnight.

Trichlor: (1300/56000)*Level = 7*2.5*0.61 so Level = 460 ppm CYA
Cal-Hypo: (1300/56000)*Level = 7*2.5*0.7 so Level = 528 pp CH
Chlorinating Liquid or Bleach: (1300/56000)*Level = 7*2.5*1.65 = 1244 ppm Salt

So you can see that with sufficient water dilution, the pool is manageable with Cal-Hypo (that was waterbear's point) with only slightly elevated CH levels that should be no problem and can easily be compensated (if necessary) with a lower TA and/or pH. You can also see that using chlorinating liquid or bleach isn't an issue with the salt level either. It's Trichlor that's a problem with its high CYA level. In fact, if you really do have a lot of water dilution, then Cal-Hypo has the benefit of replenishing calcium that you'd otherwise have to replenish with other means unless your fill water had very high CH to begin with.

[waterbear]

However, trichlor is not the first choice for a commercial pool and is, in fact, not permitted at all in some localities in commercial pools.