Pool Water Tests - Conflicting Results

homerlex said:

My own results seem to be more in line with the last two
places. How could there be such a difference in opinion on
pH, Alkalinity, CYA, and hardness?

Does the first place not know what they are doing or do
they know something that the other do not know? I'm
leaning tword the former.

Accurate and reliable testing is very expensive. It simply
isn't available with methods like your home kit or the in-
store testing. We may naively want to believe it works, but
the cold truth is that it can't be trusted.

Most likely: (1) The first place is dangerously incompetent.
(2) The others are just using colorimetric tests like you do
at home, and these are necessarily very crude to start with,
and often spoiled. Given the unknown condition of the
reagents and the vagaries of reading subtle color changes in
unknown light by uncritical persons, the figures agree
within the expected error. This error is so large as to make
the figures useless for anything but very crude
prescriptions.

The water testing is just a gimmick to get you into the
store and to sell you stuff. Your results how unreliable and
inaccurate it can be, to the point of being utterly
untrustworthy.

You have to do your own testing and learn to do it reliably.
I like the big Pool Time test kits; they come (or used to)
with coupons for several years of free annual refills via
mail to keep the reagents fresh and accurate.

If you want to do testing right, see hach.comhach.comOpen ↗
and omega.comomega.comOpen ↗ .

homerlex says...

Quoted message said:

They took the test and said your alkalinity is 26 you
need to add 50lb of alkalinity up. Since I had just
tested my self I did not believe the results. Besides
this being low the wanted me to bring it up to 125
minimum. This is strange to me too as I have always been
told 80-120 for my plaster pool. I questioned them and
they stuck to their guns. After I left I noticed on the
sheet they had something called Adjusted Alkalinity which
is much lower than Alkalinity - I don't know where this
adjusted value comes from but it was too late to ask.
They use a system called "alex" by Bioguard.

I believe Adjusted Alkalinity refers to the idea that the
cyanuric acid stabilizer in the water tests as alkalinity,
but doesn't behave that way with respect to scaling or
corrosion. They make an adjustment to remove the "false"
part of the alkalinity.

This is a controversial interpretation, and in my experience
since 1979, it just doesn't work in practice. The alkalinity
test in my Taylor kit produces results which seem to work
fine without making any adjustment. In other words, I keep
the unadjusted TA within the 80-100 range, and over the
years have had no scaling or corrosion. Also, pH tends to be
stable in that range.

If I add the large amounts of sodium bicarbonate which would
be called for by the adjusted number, it just makes the pH
spike, and I end up having to add acid every day to bring it
back down. Then when the ph has stabilized, I measure TA and
find the unadjusted value to be 80-100. So in my experience,
the whole exercise just encourages sales of bicarb, then
acid, only to leave you right where you started.

If Alkalinity Up is really bicarb, as I suspect, then their
recommended addition of 50 lbs is just silly. That would be
40 lbs in my 18.6K gallon pool, which is 10 big boxes of Arm
& Hammer baking soda. If you really needed that, I think you
would already be experiencing severe corrosion problems.

The other reading from store #1 that seems out of line is
the CYA measurement. Even with Richard's warning about the
accuracy of these tests, I don't see how they could get a
CYA reading that is essentially double what the other
stores get.

If I were in your shoes, I would not let store #1 measure my
water in the future. It appears that all of their errors (if
that's what they are) tend to produce larger sales of
chemicals to you. Of course, that could be incompetence.
Sure it could.

Peabody said:

Even with Richard's warning about the accuracy of these
tests, I don't see how they could get a CYA reading that
is essentially double what the other stores get.

The common CYA test is based on a precipitation reaction
which is very difficult to read, and rapidly loses precision
in the upper ranges.

"Peabody" <[email hidden]> wrote in message =
news:4sQrc.788$0d6.705@lakeread03...
:If I add the large amounts of sodium bicarbonate which would
:be called for by the adjusted number, it just makes the pH
:spike, and I end up having to add acid every day to bring it
:back down. Then when the ph has stabilized, I measure TA
:and find the unadjusted value to be 80-100. So in my
:experience, the whole exercise just encourages sales of
:bicarb, then acid, only to leave you right where you
:started.
--------------------------------
--------------------------------
I too have been down that full circle . But I'd like to add
a different slant to this problem of inconsistant values
from one dealer's test to another. Last night I shaved and
splashed cologne on. A few minutes later I submerged my
water bottle for the pool chemical test. The pH reading was
way off from the day before. What was happening was the blue
cap that covers the kit so it can be shaken was being
contamenated when I touched it. It's happened before so it
wasn't difficult to figure out. Cigarette fingers will
contamenate the water too. So with this in mind, water for
testing could be tainted by the pool owner or by the
dealer's help, like in the case of smokers.

I suppose if your water gets tested by someone just coming
off from a smoke break it could very well be quite different
than your own test (unless you smoke too 🙂

mark_

Along the same lines, if the person doesn't wash their hands
after a toilet break your TDS could be artificially high.
Just kidding. mark_

Hmm - so I guess next time I shouldn't use my urine test cup
to bring in my pool water sample then ;-)

Quoted message said:

Along the same lines, if the person doesn't wash their
hands after a toilet break your TDS could be artificially
high. Just kidding. mark