Thanks To All!! Clear Pool At Last

[chem geek]

Chemicals you add to your pool usually mix rather quickly. Usually within an hour, your entire pool will have some of the chemical you've added to it. I did a test using some colored dye and found that when the pump was running and when I poured it over the return jet in the deep end, it spread fairly evenly throughout the pool within a half hour (most of it within 15 minutes).

Now there are some websites that I've seen that say you have to wait longer before measuring pH because it takes a while to stabilize, but I've never seen any chemistry justification for that. All of the reactions that I'm aware of in the pool are very fast (except for chlorine breakpoint). Only the slow pH rise due to outgassing of carbon dioxide is very slow and that will never stabilize since you always keep your pool intentionally out of balance in order to maintain a TA level (with a pH near 7.5).

So my opinion is that you can test your pool chemistry an hour after you've added chemicals and you are likely to get a decent result -- so long as you have your pump running the entire time.

Richard

[karenkr]

Re-tested my pool. The PH and the TA did not change.
PH 7.8
TA 160
Should I add 28oz. more (per Bens chart)? I guess I am afraid I will add too much.
Suggestions???
Chlorine 8 would that have anything to do with my ph?
Thanks
Karen

[chem geek]

Re-tested my pool. The PH and the TA did not change.
PH 7.8
TA 160
Should I add 28oz. more (per Bens chart)? I guess I am afraid I will add too much.
Suggestions???
Chlorine 8 would that have anything to do with my ph?
Thanks
Karen

Karen,

Did you ever tell us the volume in gallons of your pool? 28 oz. of Muriatic Acid into a pool of 16,000 gallons would lower the pH to 7.44 and the TA to 153.5 so either you have a much larger pool or something strange is going on. With the numbers you show, if you have a larger pool than you won't be adding too much.

Are you trying to follow the procedure in this thread to lower your alkalinity (TA)? If you want to stop fighting the pH rise and frequent additions of acid, then you'll need to follow the procedure to get your TA down to 100 or maybe even 80. Ben's procedure for lowering TA in the referenced thread has you add a lot of acid to get your pH down and then has you aerate which has the pH rise and you add acid to keep the pH down, all the while your TA will drop.

Let us know your pool size in gallons so I can roughly calculate what should happen when you add acid.

There's also a possibility that your high chlorine level is fooling you with your pH test. Usually a level > 10 will cause you problems, but maybe 8 is enough to cause concern. You are kind of in a difficult situation with high chlorine and trying to measure pH (more on that in my next post).
Richard

[karenkr]

My pool size is 35000 gal. I was gong by Bens chart. Just wanted to lower the TA mainly and bring Ph down to 7.2.
Change of subject: did you see my other post on CYA tablets? Need some help there too!!!!

[chem geek]

With your 35,000 gallon pool and also adding in the 120 ppm CYA that I forgot about (since that also buffers pH), the 28 ounces of Muriatic Acid would have your pH drop to 7.66 and your TA drop to 157 so you might not have noticed this.

Also, as for testing pH with high chlorine, you can add one or two drops of Sodium Thiosulfate (chlorine neutralizer) which is the same reagent you use in your TA test and mix before you add the pH Indicator Solution. Unfortunately, the Sodium Thiosulfate will raise the pH and give you a falsely higher reading, but only by about 0.1 or 0.2 pH so at least you can get rid of the high chlorine to make sure that you aren't really falsely reading a high pH. My guess is that you are reading correctly since your high TA will pretty much force your pH up, but I'm just giving you another alternative to make sure. In general, you don't use Sodium Thiosulfate with the pH test.

I'll check your other post on CYA tablets and respond to that separately.

Richard

[waterbear]

[quote=chem geek

So my opinion is that you can test your pool chemistry an hour after you've added chemicals and you are likely to get a decent result -- so long as you have your pump running the entire time.

Richard[/quote]
I agree with this based on my limited knowledge of chemisty and from my own observations!