Restored pool, new water

[Kaa]

I restored a small pool (4500 gal) with a vinyl liner. It's full of municipal water now, the pump/filter/SWG should go online tomorrow.

I ran some tests on the new water:

CH 50
TA 30
FC 0
pH 7.3

In the evening I dumped some liquid bleach in to bring up the FC to about 5 (realized later it was a bit of overkill)

Next morning rerun the tests

CH 50
TA 60
FC 5
pH 7.4

re-tested TA, still 60. Weird.

In any case, questions.

I've heard both that for vinyl pools CH should be as low as possible, and that you shouldn't let CH get too low because it will leach plasticizer out of vinyl and it will become brittle. Any opinions on the matter?

Should I bring up TA a bit or it's fine?

For the SWG I intend to bring CYA to 70-80 and FC to 5-6. Should I adjust anything in the rest of my initial water chemistry before starting to dump in CYA and bleach?

If I want to add borates, does it matter at which point I do this?

 

[mknauss]

Your CH could go up to 100 or higher. Some say it matters for the vinyl, some say it doesn't. You could use Cal Hypo to chlorinate with for awhile and that will boost the CH.

The TA is fine at 60.

Why borates??

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[Kaa]

Borates because TFP told me that they will help to stabilize the pH and that they will make the water sparkly, silky, etc. with no downsides. Are there downsides?

 

[mknauss]

Downsides are cost. I doubt you are going to have an issue with pH with your low TA out of the faucet.

If do borates, use Boric Acid. Less impact on pH.

If you want the silky, sparkly, etc, add 1000 ppm salt. Same thing.

I did not remember the SWG in your first post. So the salinity for it will achieve the same thing.

 

[Richard320]

Unless there's some kind of warranty requirement for the liner, don't stress over the CH. Many millions of pool owners over the years have maintained their pools with nothing but a cheap two way test kit or wildly inaccurate strips completely blind to the CH and you don't hear about pool liners suddenly bursting very often. Keep tabs on it, sure. High CH can still cause scale formation even in vinyl. Fuss over it? No. Raise it with Ice melt or cal-hypo? Whatever you want to do is fine - so long as you understand what you're adding and you don't add stuff you don't need.

The TA jump is worrisome. Next time you test it, wipe the tip of the R-009 with a damp towel before drops. If yours is a new test kit, it may have static buildup leading to small drops and falsely high readings. If TA is 30, raise it. If the 60n turns out to be accurate, it's fine.

Do be aware that CYA is acidic (as is trichlor and dichlor) so when you add it, your pH and TA may go down lower than you'd like. In which case, adjust the TA first and then see if the pH still needs raising.

As for borates, the time to add them is when you have the chemistry dialed in and you are completely at ease with testing and balancing. Otherwise you're just adding one more variable to an already confusing equation. Also keep in mind that the season is coming to a close, and you may lose a bunch of water over the winter, and with it, the borates you just added.

In the same vein -- get things balanced before you add the salt, then let it dissolve and circulate for 24 hours, then start the SWG. Tip: if it's all nicely balanced, you can put kids in the pool to toss the salt around and swim through it and so on. They'll enjoy it and it'll mix real good without you having to brush it around.

 

[Kaa]

Kids can (and did) go into the pool if there's reasonable pH and sufficient FC. They do help to dissolve and mix things

I added about 3/4 of the estimated amounts of CYA and salt, we'll see how it goes and adjust accordingly. I'll keep an eye on TA, if it remains sufficiently stable I'll consider the very first reading a fluke. CH I'll eventually raise to 100-150, but there's no hurry about that at all and the season does end soon.

 

[Kaa]

An update: the pool chemistry seems reasonably stable except for TA. pH is 7.3-7.4 and doesn't move. With TA the initial reading was 30, then I got two readings of 60, now after five days the test (TFP-100) showed 90! Re-test after a day showed 80.

What got added to the pool in the meantime: liquid CYA to bring it up to 40, pool salt to get to about 3500, and liquid bleach to maintain the chlorine. None should affect the TA as far as I know. I'm not particularly worried because it's a vinyl liner pool, CH is very low and pH seems to be fine, but I don't like chem values to jump around like this without a good reason.

 

[mknauss]

A note on the TA test - from Extended Test Kit Directions.

Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by wipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop.

 

[Kaa]

causing the drops to be smaller than usual and making the test read higher than actual.

I've got readings of 30, 60, and 90. That's 3, 6, and 9 drops. I don't think smaller drops are going to be a sufficient explanation.

 

[getreal720]

I've got readings of 30, 60, and 90. That's 3, 6, and 9 drops. I don't think smaller drops are going to be a sufficient explanation.

You don't think that.. but you don't know that either. It's worth the extra few seconds of effort to rule out the drop size being variable. The variation in drop size could
be more than what you may think it might be. If the drops are 50% smaller then yes, that is quite significant. Testing error also factors in. Are you being very precise
in the amount of pool water you are using for the test? Is the graduated cylinder cleaned well since the last testing effort? Are your testing reagents fresh?