Unstabilized chlorine tablets?

[camp po]

I take care of a commercial pool with 56,000 gal. of water. Currently, we chlorinate with 3" dissolvable tablets in constant feeders. The problem with the amount of stabilizer already in the tabs. My cynauric levels are too high, but I have no way to control it...other than replacing all the water like my pool supplier suggested. My question is...do 3" tablets WITHOUT stabilizer exists? As I search this type of chlorine on other sites they all seem to have the same amount. If they do not exists then I'll have to change how I chlorinate which will probably be the topic of my next post . Any help?
Thanks!

[aylad]

Hi, and welcome to the forum!

Ben is really the only one around here with commercial pool experience that can help when you start discussing how to chlorinate without tabs. If he hasn't checked in here by then, I'll shoot him an email and ask him to take a look at this post.

In answer to your question, there are cal-hypo tabs that do not contain stabilizer, but the ones on the market now are junk--get mushy and completely dissolve way too fast to be used as a feed system. Besides, the chemical reaction that occurs when they break down provides quite a bit of heat and makes them unsafe to use in a closed feeder. It would also be a real mistake to use them in a feeder that previously used trichlor, because explosions can result when those two are mixed. There are also lithium tabs, but they are extremely expensive and would not be suitable at all for a commercial pool, simply due to the cost. I don't even know if they would work in a feeder for a pool that size.

So...the short answer to your question is that there are other tab forms that are not stabilized, but none that would work for your situation.

Sorry, I know that's not the answer your were hoping for!

[chem geek]

The following are chemical facts that are independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

CYA isn't "added" to chlorine. Trichlor and Dichlor products are a specific chemical form that is a combination of chlorine attached to CYA. Cal-Hypo is similar but isn't pure and the highest concentration you can get is around 73% or so and with Cal-Hypo the higher the concentration the more flammable and less safe in storage.

You need to use unstabilized chlorine for at least the bulk of your chlorine usage. That means chlorinating liquid or bleach. The volume of product needed is much higher than that of Trichlor because Trichlor is around 90% Available Chlorine while chlorinating liquid is around 11% and bleach 6-7%. For dosing, there are peristaltic pumps you can use. Another alternative would be to use a saltwater chlorine generator.

[camp po]

Thank you both for your input. I tried replying earlier, but it seems since I registered to this forum on my lap-top I wasn't able reply with my mobile device...or maybe I can and I'm doing something wrong ( which is likely the case). Either way, I'm grateful for the help. Your answers have confirmed what I've suspected all along...I need to start looking at other forms of chlorinators. I just needed to rule out the 3" tablets route. So I have read the FAQ's post which was very helpful and did answer many of my questions except for 2...can saltwater generators be used with commercial pools? and b/n saltwater generators and automated liquid chlorine systems, which one can I set and not worry about for a week while I go on vacation?
Chem geek, my CYA has been high so your "technical" explanation is helpful. So to clarify, using Trichlor tablets as one's main form of chlorine isn't recommended. So, if that's what your saying, how/why does one use Trichlor?

[waterbear]

You might want to look into changing over to a cal hypo feed system for commercial pools. They are pricey but they work well. Another alternative is a SWCG. There is always a peristaltic pump and chlorine tank for sodium hypochlorite, with or without orp control (I would forget the orp control personally.)

[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.