Muriatic Acid w/ Vinyl pool

[gdubs]

I have a vinyl pool, and have been told i should never use muriatic acid to decrease the ph, only dry acid. Does anyone on this forum use muriatic acid w/ a vinyl pool? If so, does it cause any damage.

Thanks,
gdubs

[aylad]

I use muriatic acid instead of dry acid--it's much cheaper and you don't have to use nearly as much to get the same effect. My vinyl pool is on its 7th season and I have no damage due to the use of muriatic. I pour it very slowly as far out from the edge as I can reach, and into the return stream so that the return stream dissipates the acid before it can sink to the bottom.

CAUTION:
Muriatic acid is very corrosive, obviously, and will do major damage if it comes into contact with your liner, or if you breathe the fumes. I do have a couple of small holes in my concrete deck where it splashed out of my container while being poured and didn't get washed off. I have in the past splashed it on my hand and it was no big deal, but I immediately immersed my hand into the pool to wash it off. I do always wear safety glasses, and I usually wear gloves while handling it. I will tell you from experience that if you get a whiff of the fumes it is very painful and feels as if you'll never get another breath again. Make sure that you and any other people or pets around you are upwind of the stuff while you're pouring it. To decrease the danger of causing splashes to your liner, you might try pouring your measured amount of acid into a bucket full of water and mixing before pouring it into your pool. (NOTE: ALWAYS add acid to water, not water into acid). If you're careful and respect the stuff, it is very effective and just as safe to use in a vinyl pool as dry acid.

Janet

[CarlD]

I take a 5 gallon bucket and fill it with about 4 gallons of water and pour the muriatic acid in there first to dilute it. THEN I pour the mixture into the return stream, not straight to the bottom.

[mickey4paws]

The stuff sounds scarey :eek: I used some dry acid last week to lower my TA but it didn't bring it down enough so I am also considering using muriatic acid with my vinyl lined pool.

[CarlD]

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).

[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....