Chlorine tab question

[waterbear]

P.S. Tabs in the skimmer verses a floater will not change anything

Tabs in the skimmer can potentially damage your equipment. It is the equivalent of pouring acid into your skimmer. If you have a cartridge filter they will damage the cartridge! Not too good for a pump or heater either!

[Mariza]

So question then...how long does it take the tabs to build up
unacceptable CYA levels? I currently have a pool with probably
only trace amounts of CYA. I bought a tub of the 3inch tabs before I
found this site and read up on the BBB method.

I think my pool is around 22000 gallons, plaster IG. We switched from
Bacquacil to Chlorine about 3 weeks ago. I just finished cleaning out the algae /leaves and haven't managed to get the chlorine to my proper levels yet. I started on liquid bleach (6%) and haven't used tabs at all yet.

Mariza

[aylad]

It depends on your starting CYA level, how fast you have the floater set to erode, and what levels you consider unacceptable. MOst people like to shoot for the 20-40 range. Others run theirs higher. It all depends on how much chlorine loss you have on average, and how diligent you are about daily chlorine additions. The tabs will continually drive your pH down, so if you're already having low pH problems, I would skip the tabs and stay with bleach.

Janet

[chem geek]

Tabs in the skimmer can potentially damage your equipment. It is the equivalent of pouring acid into your skimmer. If you have a cartridge filter they will damage the cartridge! Not too good for a pump or heater either!

You are correct that tabs in the skimmer can corrode equipment due to the high acidity, but it turns out this only happens to a significant extent if you are cycling your pump. If you leave your pump on 24/7, I originally thought this would put too much acid through the system, but a quick calculation showed that it wouldn't since the puck still took more than a day to dissolve.

One 3" puck dissolving in my 16,000 gallon pool with TA of 100 changes the pH by less than 0.1 ([EDIT]this doesn't count the additional 0.1 decrease in pH that occurs when the chlorine gets "used"; the tablet also[END-EDIT] increases FC by about 2.5 and CYA by about 2.1). If the puck were to completely dissolve in the skimmer in the time for one full turnover of water in the pool, say 3-4 hours, then the pH drop in that water stream would be 0.1, but since it takes longer to dissolve than that, the pH decrease [EDIT]in the water from the skimmer[END-EDIT] is actually smaller.

On the other hand, if the pump is not always on, then the puck in the skimmer will dissolve into stagnant water and the pH can drop to very dangerous levels as evidenced by my thermometer that corroded (this all happened when I first started my pool 3 years ago and stupidly used Tri-Chlor tablets). Then, when this very low pH stagnant water is first streamed through the pump when it turns on, this burst could cause corrosion in the equipment [EDIT]and damage to the cartridge filter[END-EDIT].

Now I am not recommending that people put pucks into their skimmer. I think that's too risky to do on general principle, but it does appear that the end result depends on whether the pump is always on or not.

Richard

[waterbear]

The point is most people do NOt run their pumps 24/7..once again real world usage, real world advice.

[chem geek]

The point is most people do NOt run their pumps 24/7..once again real world usage, real world advice.

That's true, but Waterdragon, who posted the initial question, said "I always run the filter 24/7" in his post so that's what got me thinking about the distinction. I probably wouldn't have even considered it otherwise. Anyway, you are right that the bottom line practical conclusion is not to put acidic tabs (like Trichlor) in the skimmer.