Using tablets as a supplement for granular?

Hi. I have a 40k gallon, in-ground pool with vinyl siding and a DE filter. I usually add 6 to 12 grams of granular chlorine daily, depending on temperature, recent or upcoming rain, etc. For awhile I have been under the impression that chlorine tablets where simply an alternative to granular chlorine, but I did not like the idea of using them because I felt I would have less control over the chlorine levels than with granular.

Recently I was told that the correct use of tablets is to keep chlorine levels steady over the course of the day, and to act as a 'supplement' to granular so less can be used.

I was hoping someone here could clarify the matter for me, and perhaps give me some tips on how often I should be adding granular to a pool of this size were I to go with the tablet-supplement course of action?

Thanks!

Chlorine is chlorine once it is in the pool. The tabs have CYA in them and are fine to use if your CYA level is not too high. But make sure there is no copper in them You do not want copper in your pool. Some people use them when they go on vacation to maintain some chlorine in the water.

Granular is either cal-hypo or dichlor. If it is dichlor, it also adds CYA. If it is cal-hypo, it adds calcium

Another difference is that granular can be used to shock a pool whereas you cannot shock with tabs.

Do you have a K-2006 kit? If so, post a current set of readings.

I use Chlor-Brite granular, which is a dichlor. I only have the Taylor basic test kit for Chlorine and PH levels, which I keep within normal levels (7.5 for the Ph and about 2.0ppm for the chlorine). I have poor color vision that makes it difficult for me to accurately read the different color gradients on those tests though, which is part of what keeps me from buying one of the more complete test kits like the one you mentioned. Still, I have not had any trouble keeping the pool algae-free.

If you use trichlor and dichlor without periodically checking CYA levels, you may end up with algae because as CYA increases, so must chlorine. Take a look at the Best Guess Chlorine Chart in my signature below for more info about that.

Thanks, I probably should get a more comprehensive test kit like the one you mentioned. Better safe than sorry, after all.

But, with the tablets, is that the 'proper' way to use them, as a sort of supplement between less-frequent chlorinating?

Some people use them as their only source of chlorine until their CYA gets too high and then they switch. Some people only use them when they go on vacation. Some people use them along with other types of chlorine. There is no one "right" way to use them. Personally, I don't use them. I use only bleach and just add my CYA separately when I need to increase it.

I decided to go ahead and order the K-2006C testing kit so I can keep better track of my chemical levels. Since it won't be here for a few days, I got a pool store water test done. They say my calcium hardness is low at 100 ppm, total alkalinity is low at 60ppm, and that phosphates are high at 200ppm. CYA tested at the lower end of normal at 30 ppm.

They wanted me to buy a bunch of stuff but I wanted to come here and see what you guys have to say about where I should go from here. The pool is looking fine so there's no rush. Would it be better to just wait for the kit to arrive so I can take the measurements myself?

Thanks

You have a vinyl pool. No worries about low calcium. Pool stores are notorious for trying to selling people calcium when they don't need it.

Yes, just wait on your kit.

This is a good question and one ive been wondering about myself. I am strictly a granular user, hth from walmart. Iv'e noticed my ph starting to rise and was wondering if tabs could help me with that. i may try some.

Bosch, be sure you test your CYA first to make sure you have room for any increase since those trichlor tabs have CYA in them.

Oh yes, for sure. I do know that my cya isn't very high, about 40. :(

Hi, sorry for the delayed response, I just did the testing with my 2006C kit today. Here are the results I got:

FC: 4.0 ppm

CC ~2ppm

7.3 PH

60ppm TA

no calcium hardness

50ppm CYA

The high CC level is a result of me not realizing the significance of CC until I read through the manual that came with the kit. What type of shock would be recommended considering these results? Hopefully they at least make sense since this is my first time using the kit.

Thanks!

Do you have algae or have you recently? If not, I am suspecting a testing error in regards to your CC reading. Can you explain how you did the chlorine test so we can verify that you did it correctly?

I followed the instructions in this video:

http://www.youtube.com/watch?v=oa8iq8htR-s


I did have a small algae problem about...one and a half weeks ago, I think. I let the DE filter (a Hayward Perflex) go too long without a backwash (since opening the pool in early June). I noticed some algae buildup beginning to accumulate on the bottom, and then noticed a slightly green cloud come from the return line after starting the pump one day.

I backwashed the filter, and the way I do it is I let the majority of the waste run out of the filter, then I disassemble the filter and clean out the tub and the filter 'fingers' completely with a gentle hosing. So when I put it back together it's entirely fresh DE in the filter (although the main reason I do this is because it causes less of a mess than blasting the dirty DE out via the back line, which is a problem because I have poor drainage in my yard). So I did that, vacuumed and the algae was gone within a day or so, but it was very slight to begin with.

The pool is currently pristine, although some people have complained that the water makes their eyes burn slightly. I've noticed it as well, though it is very slight and I don't know if it's out of the normal range for a pool. This has caused me some concern regarding CC levels.

That all said, my brother redid the test today, after not chlorinating yesterday. He found FC levels to be 2.5ppm and no CC.

Just an update, me and my brother re-did the test again today and found zero CC, so I suppose my original test result was in error, and there is no CC at the moment.

I suppose that means there's no reason to shock right now?

Probably not tho it wouldn't hurt to shock. Just be sure you keep your chlorine in range per the Best Guess Chlorine chart in my signature. If it dips below the minimum required level, you risk an algae bloom.

Thanks again Watermom. Getting back to the tablet question, my brother voiced concern that the floating tablet dispenser could conceivably get stuck in the corner of the pool and, over time, bleach out the liner. Is there any reason to worry about that?

It is possible.

When I first had my pool before I found this forum, I used Trichlor pucks in a floating dispenser and it parked itself by stainless steel bars in my pool. The acidity and high chlorine levels form the pucks rusted the two mounts closest to the feeder and I still live with that rust to this day -- it's a reminder to me of the hazards of using Trichlor pucks near surfaces that are sensitive to acid or high chlorine levels. Vinyl liners are sensitive to acidic conditions in particular while the high chlorine level may bleach out the color.

Interesting. So, it could conceivably be better for the liner to keep the ph on the baser side of the normal range?

You definitely do have to monitor your pH closely if you are going to use trichlor.