Pool store results vs my ps223 results!

Pool store...........PS223
PH 7.6................6.8-7.2 (not quite 6.8, but not 7.2)
FC 5.6...............10 (their equipment only reads up to 5.6
CC .4............... .5
CYA 11...............30
ALk 88...............120
calhard 241.........240


Sooo I'm kind of in a dilemna as to who is right according to my ps223 results my water is prefect and according to their's I need to add CYA and ALK. Pool is looking pretty good...it was clear yesterday, so i vacummed and swept it, so its blue and cloudy now.

I'm wondering how you guys would decide which one you trust more? I guess I'm skeptical of the pool store because it always seems like at least one of his vials has something wrong and gives a totally whack reading...this time one read 0 alk and he redid it and it read 88. hmmmmm

I had a similar experience with the pool store reporting low alk. It seems the pool store test only tests for carbonante alk, not all the other stuff that makes up alk (borates, etc).

Ignore their reading of 11 CYA, that's crazy, as nobody can tell CYA to 1 unit. Your Ca is fine, for a gunite pool or otherwise.

Michael

If the pool store using LaMotte Waterlink UDV's? (Little plastic vials of reagents that they inject water into?) If so, each vial needs a certain developement time or the results will be off, particularly CH and CYA. Some of the vials should not be read before 1.5 minutes have elapsed for accurare retults. If they are using Taylor reagents then most likely the testing the testing is not being done correctly to endpoint on the titration tests. As for the difference in pH....that one has me stumped.

Yeah they are little square plastic vials he squirts water into. Then a machine reads the results. The Ph has me confused too...maybe i'll go buy some strips and see what they think.

LaMotte Waterlink...same as I use as work. If it is done right it is extremely accurate. The FC is supposed to be read as soon as the water is put in and the vial is turned over 3 times. The other tests are read in order but proper time for test development is needed or the results might be low. I have checked on my own pool the LaMotte testing against Taylor's and Ben's kits and have gottend basically the same results within normal testing variances. As I have stated in other posts testing is only as good as the person doing it and I would trust most of the members in this forum to test my pool before I would trust most pool stores! Strips are not going tell you much of anything...don't waste your money! If your chlorine was above 10 ppm that would cause the LaMotte test to read high on pH...all pH tests have interferance from high chlorine levels and LaMotte's is only corrected up to 10 ppm chlorine for the pH. I believe that Taylor's and Ben's is corrected to 15 ppm. That could explain the problem with the pH results.

ok I'm losing faith in the pool store. Since my last alk reading of 88 I have added nothing to the pool. Today they tested my water and said the alk was 126. My ps223 still says 120, soooo I'm going to start trusting my ps223 more.