Granular chlorine not dissolving

[travs69]

Wife went to shock the pool 2 weeks in a row and both times I have gotten up the next day and the chlorine is just sitting at the bottom of the pool. Scrubbing it gets it to dissolve. She says she is pouring it into the pool directly in front of the return water jet. I am still reading about the benefits of using liquid but I'm not ready for that switch yet.

Is this a problem with the chlorine, the pool, or the technique?
Any recommendations on a good test kit? (Currently I'm using the little test strips with the 5 different things on it.. not easy to read at all)

Thanks in advance for help.


24' above ground pool.

[chem geek]

It sounds like this granular chlorine is Cal-Hypo. If it is, then this is better to pre-dissolve in a bucket of water before adding it over a return flow. Just keep in mind that with Cal-Hypo, for every 10 ppm Free Chlorine (FC) that it adds, it also increases Calcium Hardness (CH) by 7 ppm.

As for a good test kit, get the Taylor K-2006 kit at a good online price here or get the TF100 kit from tftestkits(dot)com here with the latter kit having 36% more volume of reagents so is comparably priced "per test". Both of these tests use FAS-DPD for the chlorine test which will not bleach out at higher chlorine levels (can measure up to 50 ppm) and is accurate to 0.2 ppm or 0.5 ppm depending on sample size and you simply count the drops until the sample turns clear. Read more about it including a video demo here.

Richard

[travs69]

I just checked, it is HTH Super Sock It.

My parents and my best friends use the same product the same way.. I seem to be the only one having problems??

Is calcium hardness the same thing that makes water "hard"? My understanding is we have hard water (we are rural-ish). Will this cause me problems in the long run?


Oh yeah.. thanks for the help!

[chem geek]

HTH Super Sock It is Cal-Hypo (53% Available Chlorine). For every 10 ppm Free Chlorine (FC) added by this product, it also increases Calcium Hardness by 7 ppm.

If you already have hard water, then your fill water may already be high in CH. If you keep using a Cal-Hypo product, then your water can turn cloudy and eventually cause scaling, especially if the pH goes up or the Total Alkalinity (TA) is high.

As for why your product doesn't dissolve in your pool as quickly as with other pools, it could be that yours is more saturated with calcium carbonate already.

After you get your good test kit, you can use The Pool Calculator to see what the saturation index is for your pool -- if it's high, then you shouldn't use Cal-Hypo for chlorine.