Muriatic Acid w/ Vinyl pool

[mickey4paws]

It IS a little scary--you just have to follow the rules, though and you'll be safe. Dry Acid isn't as safe as it seems, but it's a lot easier to use than Muriatic Acid. Buy the generic stuff.

Another way to lower your pH is to use Tri-Chlor pucks. But this is only a good way if your CYA (stabilizer) level is lower than you like. Pucks lower pH and raise the CYA level fairly quickly. I use them when I'm in that situation (as I have been this year).

I know this post is a little old, but I do have a question. What effect does the Tri-Chlor have on alkalinity? Does it only effect PH, or does it also bring down TA?

[chem geek]

As with any acid, it brings down both pH and TA together, though the pH drops more than the TA. This assumes you are using Trichlor for a while so there is chlorine usage/consumption. For example, adding 3 Trichlor tabs/pucks to a 10,000 gallon pool starting out with a TA of 100 ppm and pH of 7.5 would end up with a pH around 7.0 and a TA of 88 ppm. In practice, the pH might not drop that much since there will likely be outgassing of carbon dioxide during that time. The cumulative FC added and presumably consumed is 16 ppm and the CYA increase is 10 ppm.

Don't forget that for every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

Richard

[mickey4paws]

As with any acid, it brings down both pH and TA together, though the pH drops more than the TA. This assumes you are using Trichlor for a while so there is chlorine usage/consumption. For example, adding 3 Trichlor tabs/pucks to a 10,000 gallon pool starting out with a TA of 100 ppm and pH of 7.5 would end up with a pH around 7.0 and a TA of 88 ppm. In practice, the pH might not drop that much since there will likely be outgassing of carbon dioxide during that time. The cumulative FC added and presumably consumed is 16 ppm and the CYA increase is 10 ppm.

Don't forget that for every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

Richard

Thanks very much, Richard. I chlorinate using a SWG and sometimes have to use muriatic acid to either bring down TA or PH. I've never used a puck before but I assume you have to leave it in a skimmer or feeder for a while and so it sounds like it wouldn't be good for my purposes. I have a vinyl lined pool and I'm still a little nervous about using the muriatic acid. I do pour it into a 5 gallon bucket first and then pour in front of the returns. I also have some dry acid but I hear that's not so good to use with a SWG, but I can't remember why.

[chem geek]

The dry acid increases sulfates in the water and that is supposedly not good for SWGs though I don't know why -- probably interferes with (degrades more quickly?) their special coatings on the plates.

[CarlD]

Quick note:

If you use tri-chlor pucks and keep your pool covered, you won't get the out-gassing Chem_geek speaks about and your pH DEFINITELY will drop.

Of course, if you are using an SWG, the SWG rise in pH may offset the Tri-chlor drop.

Tri-chlor pucks CAN be used, but must be used wisely, paying attention to both the CYA increase and the pH decrease. I've used pucks more this summer than in the previous 9 seasons because the rain keeps washing out my CYA AND drops my FC levels, plus keeps the Tri-chlor from lowering the pH too much.

For that I've used a couple of boxes of Borax.

On vacation--just checking in....