OK.

Now, on to the hard part. This thread has provoked a certain amount of uh-h, 'response' in my email box. So I figure I need to wade in a bit.

Evan, you were correct that I confused the K2005 and the K1005. I'm didn't even recall that there WAS a K1005. And, without digging more than I'm willing to right now, I'm not sure what's the case regarding sample sizes and all that, so I'm happy to defer to you.

"Useless" is not the way I'd chose to describe A/B testing.

However, when you wrote
With high TA we all know it will take more acid to lower the pH to our target of 7.0 than with a lower TA. The acid demand test is a tool that will somewhat shorten what is a lengtly procedure.
I'll agree or disagree, depending on how you define "somewhat". My inclination is toward "somewhat" equals "not significantly", and especially in the context of some new to testing (like redtickbeer") an unnecessary complication.

All in all, I'm still convinced that - with a few exceptions -- TATA is the way to go with most PF users, and especially newbies.

We struggle CONSTANTLY with having to balance the need to give instructions that will work if done correctly with instructions that can be followed by confused newbies.

There are many, many significant treatment tools I mention rarely or NEVER, because it's not generally applicable here. For example, I rarely mention (and only with lots of red cautions), direct pre-filter additions of cal hypo to the circulation stream, even though it will
+ remove metals
+ dramatically improve clarity in heavily used pools
+ remove oils and gunk
+ 'test' filters for proper function
+ auto-balance pH, CA, & CH
+ and more.

Why not? Because it's too complicated and depends too much on following the instructions exactly AND because if common sorts of mistakes are made, DANGEROUS results will follow.

Likewise, I've hardly ever mentioned using peroxide and copper for instant (1-day) cleanups of swamps with 4" of sludge on the bottom. Why? Because, even though it's worked EVERY time I've tried it, I haven't worked out doses, and don't know if it works everywhere, and don't want to have to explain all the problems of clean up copper (with no cal hypo!).

So, when Carl and I say A/B testing is not very useful (Carl went further than I would in saying it was "useless") that's a viewpoint I consider to be correct on PF . . . when you keep in mind that our audience is newbies. For a few of us, PF is an outlet or entertainment or even a life interest. But for most people here, PF is a resource that's intended to help them get the chemistry stuff out of the way so they can ENJOY their pool.

In that context, the complication of A/B testing is of questionable value . . . and the question is, "Does it add more value than complication?", since it obviously adds both value and complication. My judgement is, that it adds more complication than value.

There's some background here.

Having worked with lifeguards for years, trying to get them to test pools, I've discovered regular and frequent is MUCH better than regular and infrequent. In other words, it's easier to get the guards to test the pool 1x per day than 1x per week.

Why?

Habits get build with repetition and lost with time in which no repetition occurs. There's a sweet spot that works better than others, and a 1x per week activity is outside it. It is my experiences with lifeguards, and my judgement with homeowners, that they need to test 1 - 2x per day IN ORDER TO GET INTO THE HABIT.

This is one reason I like the K1000, which allows cheap 1 - 2x per day testing.

But . . . A/B testing will never be learned that way, since it's intrinsically of episodic value: you only need it, when things have gone wrong. So, if you teach new users who come to PF to use A/B testing, instead of TATA, you have given them a skill that won't have value until the NEXT time something goes wrong. But, if you teach them to deal with the problem with TATA . . . that skill (and HABIT) simply roles on over into regular pool ops.

I still believe this is a HUGE functional benefit, but again only from the point of view that we are trying to help folks OPERATE their pool in the simplest way possible, with the lowest achievable learning curve.

Or, in other words, K.I.S.S.

Evan, I recognize that A/B testing can occasionally have value. I think it might be worthwhile to have a reference-able page explaining how to do it, so that when people come in with high TA or unknown low (or high) pH we can say:
#1 - do TATA, but check this A/B page out, since it might help you, in your particular situation.
#2 - in your emergency situation (pH maybe 4.0), read A/B since that may abbreviate the length of time your pool spends in the pH "Death Zone".
#3 - for YOU (Service Guy), A/B testing can be a useful tool. Here's the page. (Of course, my experience is that pool service guys that come to PF -- admittedly a skewed selection -- tend to have a LOWER learning capability than the average pool owner.
#4 - for you (tinker guy who likes his pool mostly as an elaborate tinker toy), you might like using A/B.

BUT, I do not think A/B testing has value as a GENERALLY RECOMMENDED PF advice-let.

Why?

Because it's awfully easy to screw up:

"OK. I got pool water in the plastic color thingie. Check.
I put the pH bottle stuff in the side that says pH. Check.
Darn. It's a weird color.
Oh yeah. I can ADD hat A/B stuff to make it change color and then count the drops.
Ok. I add some B stuff.
Darn! No change.
2 more drops. Still no change. I'll try the other kind.
I'll add some A stuff. OK. It changed.
No, it changed back. Darn.
I'll add some more. Ok. It quit changing.
Darn! It changed back again.
Ok. It quit again. Add another drop or so.
Yeah, it stayed quit. 8 drops of A stuff or maybe 10.
Now what.
Oh, yeah. Where's that darn book.
Chart, chart, chart . . . A/B chart. There it is.
Ok, 8 drops that will be 1.28# for 5,000 gallons.
How much is my pool? Oh yea, 6,000. Ok that one.
Soda ash. What is soda ash? Wait, I don't want to increase my pH.
Darn! Wrong chart.
OK. 2.29 gallons of muriatic acid.
Sheesh. I have to use that stuff?
Wait, another chart. Dry acid. Ok
3.06# of dry acid. Ok.
I got a 5# container. That should be close enough.
Ok. Dump it in.
Crap. It's all on the bottom. Will hit hurt something.
Darn. There are bubbles coming from the plaster. That's not good.
Ok. Brush it around.
Ok. All gone; all good.
Darn. It's nearly dark. Sorry kids, no swimming tonight.
(Next morning)
Crap. What the ### is this? NOW, the fleeping pH is LOW.
Screw that stupid PF place. Off to the pool store."

And, if you think that won't happen -- pretty much exactly -- you need to answer a few more questions from Intex newbies.

But, it can be worse. If you go the other way, and add a slugged A/B dose of SODA ASH, in a pool that has moderate CA and CH . . . you've got a much better than 50:50 chance of precipitaing a calcium carbonate cloud, which is slow to clear up.

So, I guess the question is, do you want to submit a A/B testing guide we can edit and post? (And I will credit you.)