Couple of Chemical questions

[Goolsbymd]

I recently purchased a house with a new salt water 8500 gallon in ground vinyl lined pool the salt cell is turbo cell t cell 15. I recently (yesterday) opened it for spring and did a water check, nice and clear with a Leslie's deluxe poolcare oto test kit (TC, pH, acid demand, and TA) per shock the #s were TC 0 pH 7.8ppm TA 80ppm after adding a pound of shock, said 1# was good for a 12k pool I ran pump all night and most of today the numbers are TC 5ppm (looked same color but scale only goes to 5) pH dropped a little to 7.2ppm and TA dropped to 70ppm(vinyl lined). So do I need a better kit to see how high TC went to accomplish shock, can I use BBB with a Salt water pool? The cell is off due to low temps and I think salt lvl was about 3300.

[PoolDoc]

You need a better kit so that you can:

1. Check your CYA (stabilizer) level, and maintain that. It's critical -- sunlight will strip your pool of chlorine without it, but if it's high, you'll have to raise Cl levels to compensate, since it reduces chlorine's activity level.

2. Check your chlorine level accurately, at levels above 3 ppm, so you can deal with algae and the 80 ppm CYA level many SWCG manufacturers recommend.

3. Check your calcium level, so you can anticipate and manage scaling issues with your SWCG and heater (if you have one). By the way, with a vinyl pool do NOT add calcium!

The most economical kit is with the high range chlorine test is Taylor's K2006. You may want to get the K2006C, which has larger bottles of reagents (2oz vs 0.75oz). There's a link to a page with links to various Taylor kits on Amazon, in my signature below.

[Goolsbymd]

Ok I'll look into another kit. Can I add bleach and follow the bbb method while the cell is off or should I just add another shock kit later if needed?

[PoolDoc]

Just like bleach, all chlorine based shocks add HOCl + -OCl once they dissolve. Do NOT use the non-chlorine shocks or the 'hodge-podge' multi-ingredient shocks, till you really know what you are doing, and are sure that that's what you want to do!

The difference between bleach, trichlor powder, dichlor granules, and cal hypo is what ELSE they add to the pool. The 'else' can be good, or bad, depending on what your pool needs. But bleach just adds salt as its 'else' -- so that's the simplest and safest option for you, till you have test results.

[Goolsbymd]

Got a K2006 kit along w/ LaMotte Borate test strips on the way. I'll wait to get them before doing anything but in the mean time.

Assuming 0 Borate in my 8500 swg pool w/ TA at 80 and pH at 7.4 (both are right now but getting long heavy rain). I have to add approx. 31lbs Borax 20Mule
1.8gal of 31.45 Muriac Acid

31 lbs of borax will raise pH 6.5 and TA by 115

Adding 2gal of 31.45 MA will lower pH by 6.7 and TA by 110

Leaving totals roughly around: 6.5pH and 85TA? Or will the Borax make my pH higher than calc. This w done mostly on pool calc.

[PoolDoc]

OK. There are two schools of thought here.

Chem_Geek, who is a frequent poster here, and who is an extremely skilled analyst and pool owner, and whose technical knowledge of pool chemistry surpassed mine 5 or 6 years ago, favors what we've call the "TCMD" method (Test accurately, Calculate the dose, Measure the dose carefully, Dump the dose in). An older version of Chem_Geek's pool chemistry analysis spreadsheet (available here: http://richardfalk.home.comcast.net/...lEquations.xls ) provided the analytical basis for "The Pool Calculator".

I much prefer the "DT" method (Dump a smaller than needed dose in, and then Test). Repeat as needed in a day or two.

Pool stores have to try to follow the TCMD method . . . because they've got to get you loaded up RIGHT NOW (so they can sell you $$) and also you may not be back, so if they don't fix you up 100% now, it (whatever 'it' is) may not work.

Of course, that's not Richard's reason. I think he just really, really likes to be completely accurate as often as possible.

But, after 25+ years of servicing very large commercial pools, usually on a weekly basis, I've learned several things:
1. Except for low chlorine or VERY low or high pH (<6.8 or >8.2), most pool chemical problems aren't an emergency.
2. Pool calculations are rarely accurate:
- There are errors in pool volumes reported (> 50% of the time!).
- There are testing errors, both because of limitations in the test methods and because of operator errors.
- There are measuring and dosing errors. (Not many owners or dealers keep a scale handy, so they can weigh out 31# of borax, and counting boxes leads to errors: "let's see, was that 11 boxes at 3.75# per box I just put in? No, wait, it's 4.75# per box! Darn!")
3. And, measuring pool chemicals is not always safe: muriatic acid and hydrogen peroxide (used with Baquacil) are both pretty nasty to handle!
4. Making large changes -- all at one time -- in several aspects of your pool's chemistry will eventually result (for most people, except Richard) in problems. For example, if you watch for it, you'll see the posts in a few months from people who tried to fix their pH, alkalinity, and calcium levels all at one time . . . and who ended up with a pool that looks like it was filled by Mayfield's Dairy!

If your chlorine is low, you need to add the RIGHT amount, RIGHT THE HECK NOW!

Otherwise, it can wait. By adding a smaller than needed dose -- when you test the next time, you'll either be on the money OR, you can add another smaller than needed dose.

AND . . . with the DT method, over time, you'll end up discovering just what sort of doses are needed, at what frequency, to maintain your pool with minimal effort and error.

Now there are exceptions to everything.

*Most* people can't handle muriatic acid for years, without a spill. That's why acid sticky here emphasizing lowering the acid bottle into the pool, before you start pouring. That way, any spills are in the pool, and not on you or your deck. But, Richard just told me a few days ago, that after years of using muriatic acid, he's never spilled any. I can't think of ANYONE else I'd believe, if they told me that, but I believe Richard. And, I'd guess that Richard has rarely, if ever made a pool volume calculation error, or a chemical measurement error, or a testing error that was based on operator error.

He is an exception, to the rule, and in more ways than one. You may be one, too.

But for most people, I think the DT approach is much better than the TCMD approach. So, *my* advice would be to put in 5 boxes of borax and a gallon of acid, and then test. If your pH is low, add another box of borax. Then add some more borax and acid every few days, till you hit the mark with both your pH and borax levels. And do NOT try to measure muriatic acid out into another container: just use the "Mark 1 Visual Estimation via the Reflected Light Level Biological Input System", to put in 1/4 gallon or 1/2 gallon. (In other words, "eyeball it!")

On the other hand, if you are as meticulous and careful and consistent as Richard . . . or if you suffer from OCD, the TCMD approach is probably best for you!