My test results vs. Pool Store...now what??

[Henrys514]

So I just ordered Ben's kit ...I'm tired of this Wal-Mart kit. I feel like I can't trust any numbers it gives me. Anyway, I took my water to the pool store tonight, then tested it myself. These are the results.

Wal-Mart Kit (pool store)

TC=1.5-3ppm (FC 2ppm)
pH=~7.6 (7.7)(acid demand=1)
TA=190ppm (115 ppm)
CH=250ppm (155ppm)
CYA=out of reagent (35ppm)
Pool stats-12,000 gal IG exposed-aggregate surface

I've posted about my TA and CH numbers before (in another section of the forum). My question is, which numbers should I believe? Pool store says alk is fine, but my test says it's not. Pool store says I need to add calcium, my test says not to. My water is clear and sparkly. However, my pH has been creeping up. I pretty much have to add 2-4 cups of acid each day. Tonight, I added 1/2 gal of 10% chlorine to get my TC up to ~6ppm and I added 4 cups of acid. I will test tomorrow morning to see where I'm at.

pH and Chlorine seem to be the only consistent numbers between both tests. My husband keeps bugging me to add the calcium too because "the pool store said so." Should I just keep on top of the chlorine and pH until Ben's kit arrives?

[waterbear]

I am beginning to believe that the Walmart kit is testing total hardness and not calcium hardness. I would wait for Ben's kit to arrive before doing anything. TA numbers are pretty far off but I have found the walmart kit to be pretty accurate on this test. What is the pool store using for testing? If they are using strips (even if read by a scanner and hooked up to a computer) I would trust your numbers. Are you doing the test properly? Hold the dropper bottle upside down when forming the drops and form them slowly. Swirl after each drop and add drops and swirl untill adding one more drop does not produce any further color change (it goes from green to reddish to very red). Once you have added one more drop and the color did not get any redder do NOT count that last drop in your determination of TA. As far as testing properly goes, the pool store might not be doing the testing properly either! If there is a different pool store around why not take a water sample their and see what they get.

[Henrys514]

The pool store is using a titration method for the TA and CH tests..no strips for any test. Then they just input the number into a computer, and I get a printout. My TA Wal Mart test goes from blue to clear not green to red. Then you multiply # of drops by 10 to get ppm. I'll have to see if there is another store around here that will do it.

Hopefully Ben's kit arrives quickly...and my husband stops bugging me about adding the Calcium.

[waterbear]

The pool store is using a titration method for the TA and CH tests..no strips for any test. Then they just input the number into a computer, and I get a printout. My TA Wal Mart test goes from blue to clear not green to red.
This is interferance from high chlorine levels. Same thing can happen with the Taylor kits or Ben's kit. Your chlorine levels must be higher than you are posting when you are doing the test! One of the indicators in the TA indicator solution is getting bleached out. The color is actually going from blue to very pale yellow. (I am assuming you have the Walmart Aquachem 6 way kit, some walmarts sell the HTH 5 way kit, I am not familair with that one but I believe it uses the same reagents as the Taylor kit)
Then you multiply # of drops by 10 to get ppm. I'll have to see if there is another store around here that will do it.

Hopefully Ben's kit arrives quickly...and my husband stops bugging me about adding the Calcium.

Hope this is helpful.

[Henrys514]

Yes, I have the AquaChem kit. My chlorine has been high lately(Saturday I had it up to 12ppm, and it's been drifting down since), but when I did the test yesterday, TC was definetly between 1.5 and 3ppm. The OTO colors are tough to read for me above 3...but this was definetly below 3. Unless something is really wrong with my test kit.

The pool store's test goes from green to red. At what ppm Chlorine is the TA test useless? I'm trying to keep my Chlorine at 5-6ppm...can I ever expect to get an accurate reading for TA if you say Ben's kit has the same bleaching out problems? Any way to get around the bleaching out problems? I know high TA is not good, especially for a concrete surface. If I need to start decreasing it, I need an accurate test to tell me so. I've been adding acid almost every day just to keep the pH at 7.6. It's been drifting up to 7.8 all the time.

Also, I noticed the book with the kit says "Water Hardness test" for the hardness. Like you said, it could be testing for total hardness, not Calcium Hardness.

[waterbear]

I believe that anything above 10 ppm will cause interferance. The Taylor kit and Ben's kit might be 15 ppm. Gotta research that to get a more definative answer. Bottom line is the chlorine needs to be in the right place before you do the other testing. pH test has the same type of problem but it will show a bogus high pH when the chlorine levels are high.

[geordie]

I had the same problem last year with the Aquachem kit. In fact, I had the problem with two different Aquachem kits last summer. I was able to rely on my TA and the chlorine-ph tests were fine, but the hardness test was invalid. To begin with, it never really turned blue, and it definitely didn't turn anything other than progressively clearer. The kicker is my chlorine was 3-5, right where it needed to be for my CYA.

I assumed I had botched the tests. I KNOW I have hard water... no doubt. I've also been doing this for so many years I was positive my chlorine readings were valid. Since my hardness isn't really relevant in my pool I didn't obsess over it, but every now and then would re-test just because it bugged me! I bought a new test kit, and had the same problem.

This year at start up I wound up getting the HTH kit because it was the only game in town (aside from Ben's which I've never ordered because I manage okay without it) and suddenly, I had measurable hardness and the test worked perfectly.

If you know anyone around with a pool and a kit, get them to run a test for you.