New poster, taking care of new vinyl liner

South Florida, in-ground vinyl pool, 7000 gallons.

We'd managed to bleach the liner pretty good and solid thanks to following pool store advice on maintenance. Based on my reading here, it sounds like we had too much chlorine.

There aren't many vinyl pools in South Florida and the tech who installed it gave a lot of advice that was contrary to the pool store advice. I've tried vetting what he said online and gotten even more confused. Hopefully, this forum will help me dispel some of the confusion.

According to the tech who did the liner, he said all we need to do is put in the powdered stabilizer, cyanuric acid hydrate, 1lb through the skimmer each month, then add a little less than a half jug of liquid chlorine weekly, also through the skimmer. Use soda bicarbinate to increase the ph as needed. The surprising thing he said was to NOT use muriatic acid, calcium hardness, and absolutely no floater chlorine tablets as that is acidic and ruinous to the liner.

Ok, upon reviewing commentary I see confirmation for the the calcium hardness since that is more of an issue with cement pools. The liner is inert and therefore doesn't present an issue. The pool store still argues with this but the tech says that their machines are all assuming concrete pools as standard.

I have not seen any confirmation for the muriatic acid comment which is a bit of a concern because we've had a pretty heavy rain that's raised the ph.

So, what is the best way of lowering ph in a vinyl pool?

Here are the current numbers:
Total Alkalinity: 160
ph: 7.8
chlorine: not present, supposedly only needed once a week, we are adding on schedule but it won't last

Our test kit says the ideal ph range is between 7.4 and 7.6 and we need to add acid now. The liner guide says 7.2 to 7.6. The trouble free pool guide linked to from here says 7.8 is good.

So, what's the real answer?

1. You can use muriatic acid, as long as you do so properly, and make sure the pump is running when you add it. See http://pool9.net/muriatic/ for more info.

2. 1/2 gallon of bleach + 1lb of CYA /month may be a recipe that generally works out on S. Florida 7,000 gallons screened pools . . . but neither you nor I know that. the ONLY way to be sure your tech is right, is to learn to test your pool correctly. See http://pool9.net/testkits/

3. TFP (troublefreepool.com) is a copycat site of this one -- though now larger and in some ways, better run -- that started during a period when I wasn't taking care of business here. For the most part, they approach pools the same way we do here, since both sites follow the ideas I developed. But there are enough differences so that it will work best if you pick one site or the other to follow. If helps, I came up with most of the ideas, CarlD, who posts here, came up with a some of the nomenclature ("BBB method", and Chem_Geek, who has analytically validated most of the ideas, posts both there and at TFP. But whatever you prefer is fine -- just pick one or the other.

4. Liners are fine between 7.0 and 8.0 . . . depending on other factors, which is why you need the kit, just to make sure some of the other factors are NOT a factor on your pool. Once you test your calcium levels, you may not need to do so for another year.

5. Meanwhile, get a cheap local OTO / phenol red kit and some PLAIN 8% household bleach, and use the two together to get your chlorine level above 2.0 ppm.

I am interested in the fact that both your tech and your store acknowledge that calcium's not needed. When I started PoolSolutions in 1996, I was the ONLY one saying that -- so far as I can tell -- in the pool industry anywhere. So, at least one of my ideas is now widely accepted.

Man, this is annoying. Was typing a reply and the token expired. Hit the back button and everything is lost. Trying again.

This pool stuff is like alchemy, lots of contradictory information and the results can be a bit perplexing.

So, where we are at right now: the pool pump has been on overnight with the addition of the new stabilizer. The test shows there's hardly any chlorine is left and the ph is still high as before. We'll add muriatic acid to the pool and also put in more chlorine. Since those two items should never be added together, the best practice guide says a half hour separation should be good.

What's the recommended technique for an algae bloom? Conventional advice is a shock treatment but I've seen contradictory advice concerning the vinyl. Hopefully I'll get a handle on this soon.

Yeah, that still happens to me occasionally. If I have to leave a post before I'm finished, I cut & paste it into NotePad, and then refresh the page. When I return, I refresh the page again (to see if there are new replies) and then open a 'Reply' window and paste the previous work in.

And you are right: pool chemistry is VERY much like alchemy, with lots of published conclusions based on the thinnest of evidence!

Don't worry too much about the chlorine / acid separation -- just don't pour them on top of each other. If you add acid at one end, and bleach at the other, you'll be fine.

Vinyl bleach-out is a topic about which there's not too much useful info. I'll tell you what I know; most of this comes from talking with vinyl product engineers.

1. PVC liner material itself isn't much affected by chlorine, but the plasticizers ARE affected by low pH (< 6.0), which can cause swelling and wrinkles.

2. Some solid color liners may have colorant IN the liner material, but . . .

3. All patterns, and some colors, are printed ON the liner.

4. Liner printing IS susceptible to bleach out, but . . .

5. Different colors, and colors from different suppliers, vary widely in how sensitive they are.

6. Generally, high end liners (like Plastimayd) are less susceptibel than low end liners, but this is not always so.

7. If there is ANY reliable info on how much chlorine a particular liner can handle, I have not found it, and I HAVE looked.

8. As CYA levels increase, the bleaching affect of a given level chlorine is reduced.

9. Any form of chlorine that remains in contact with a liner for more than a few minutes is likely to cause permanent bleaching or color change, so be very careful with relatively insoluble forms of chlorine like calcium hypochlorite or trichlor (sometimes sold as an algae powder!).

10. Just from my observations here, it appears fairly uncommon that liner bleaching occurs among users following our recommendations for overall chemistry, EVEN with rather high chlorine levels.


So . . . shock, but use a soluble form like bleach, or dichlor powder.

We've been getting a lot of rain and it's been very tough to keep the pool's ph in acceptable levels. The relatives are heading out on Friday so we'll be using a stronger set of chemicals to try to get things into balance. The pool has a distinctly yellow/green murk to it. So are algicides a good thing for vinyl? I'm not sure. We have the chlorine very high but the algae doesn't seem to care.

Read the "Best Guess" page on the chlorine / CYA relationship => http://pool9.net/cl-cya/

Then answer the following questions:

1. How are you testing? (If it's not a K2005/2006 . . . you don't really know what your CYA level is!)

2. What is your chlorine level? (if you didn't use a K2006, and your chlorine is > 5 ppm . . . you don't really know what your Cl is!)

3. Is your Cl level appropriate for your CYA level? (if you haven't tested with a K2006, you can't tell)

4. Order a K2006, so you can tell. => http://pool9.net/test/

5. Meanwhile, since you're worried about your liner, and since we (probably) don't know what your Cl or CYA levels are, get some polyquat locally and add a QUADRUPLE dose. Polyquat is a chlorine compatible algaecide, but isn't super effective against mustard algae. Neither are other algaecides, but you can 'overdose' with polyquat without causing problems. => http://pool9.net/polyquat/

Things you need know:

+ Test strips = 'guess-strips', even when computer read by dealers, ESPECIALLY with respect to CYA.

+ Liners are unpredictably sensitive to chlorine bleaching. Dark blue is the worst.

+ The ONLY non-chlorine / non-bleaching genuine sanitizer pool system is STILL Baquacil / Softswim, etc (PHMB) => http://pool9.net/phmb/
PHMB works well the first season, but is a pain after that, UNLESS you follow the guidelines in our info. It's expensive, compared to chlorine, no matter what you do.

+ Until you have accurate test results, we can't tell you what to do in YOUR pool.

Good luck!