I have a hot tub I am trying to balance the water. Both my Alkalinity
and PH were high. I put in "PH down" and of course it lowers both.
Is there a way to lower the alkalinity without making the PH bottom
Thanks so much!
Am I missing something? pH is a measure of the relative acidity or alkalinity
of a solution (actually the concentration of hydrogen ions). pH less than 7 is
considered acid (the lower the number the more acid the solution). 7 is
considered neutral. Greater than 7 all the way up to 14 is considered alkali
(the higher the number the more alkali the solution).
Asking to lower the alkalinity without dropping the pH is like asking to drop
the temperature without cooling anything off.
I don't own an operating hot tub but I did take chemistry many moons ago.
On Mon, 26 Feb 2007 14:45:58 -0500, "Mortimer Schnerd, RN"
Many people are confused by this. Alkalinity is the property of the
water that pertains to how well bases can neutralize acids. Alkalinity
acts as a buffer of sorts. If Alkalinity in the tub is low, the PH
will never remain stable. If you raise alkalinity too high, you will
find it hard to either raise or lower PH.
PH and Alkalinity are closed tied together, but they are not the same
No, I don't think you're missing anything except possibly the
terminology of the "water industry". I'm a molecular biologist, and I
consider myself to have a pretty good working knowledge of chemistry,
and I work with acids and bases regularly. In my experience (multiple
research and teaching labs, several chemistry classes), the terms
"alkaline," "basic," and "high pH" are used interchangeably, so your
temperature change analogy is correct.
However, after a few minutes of web searching, it appears that the
"water industry" (apparently someone who works with hot tubs, aquaria,
etc.) uses the term "alkalinity" the same way I would use the term
"buffering capacity". Seems like they like to say, as another poster
has pointed out, that alkalinity refers to how well a solution resists
change in pH, or the amount of acid that must be added to change pH.
So in common use, I would say you're right: alkalinity is the opposite
of acidity. But it seems like the OP has a hot tub that's basic (high
pH), and too strongly buffered. When he added "pH Down" (i.e. an
acid), the pH of course dropped, and he must have overcome whatever
buffering capacity the water had, thereby reducing the "alkalinity".
I know from experience in the lab that it's easy to overshoot your
target pH when adding acids or bases, and that buffers can be tricky
things to maintain when you try to drastically change the pH. So the
advice of others to start over with new water, (effectively make a new
buffer around your target pH), makes a lot of sense to me.
Sorry I'm not much more help on the hot tub side of this question, but
the changes in terminology are interesting. As you can probably tell,
I don't own a hot tub and I have very little experience with them, but
I'd love to be sitting in one right now.
Good luck with your pH and alkalinity adjustments,
On 26 Feb 2007 19:32:04 -0800, firstname.lastname@example.org wrote:
Hi, Andy. Another molecular biologist here. I was scratching my head
at first, too, wondering how he make his tub less alkaline without
reducing the pH. Thanks for your post; I agree that the "tub
industry" is using the term alkalinity imprecisely. I too would use
the term buffer capacity. I wonder just what kind of buffer a hot tub
uses. PBS? TAE? TBE? Tris-glycine? 20 mM HEPES?
Have a good day,
On Feb 27, 11:59 am, email@example.com (Bill) wrote:
Bill & Andy-
Thanks for jumping in here on this spa water chemistry discussion.....
I, too, was thinking that the spa/pool people were using the term
alkalinity imprecisely because it didn't make sense to me.
I figured they were trying to describe a buffered solution without
getting into the chemistry of the situation.
Having had a spa for 10+ years (moved recently) ......I was lazy &
never really put my chemist hat on but just followed the water
conditioning treatment instruction by rote.
Most of the time it worked fine but occasionally the chem got all
messed up & I would just drain the spa & start from scratch.
I think if the spa/pool industry gave people better information, it
would easier to understand what is really going on & control it.
(Mechanical engineer, I took a detour from my chemistry major 35 years
On Tue, 27 Feb 2007 19:59:57 GMT, firstname.lastname@example.org (Bill) wrote:
This has been a good thread. I've often thought the use of the term alkalinity
by hot tub companies was a little "off", but since I knew what they were trying
to get me to do, it wasn't an issue. It did sometimes make me wonder if I was
somehow mis-remembering what I learned in school. Tub and pool chemistry really
isn't that hard to maintain once you have been doing it for awhile. The basic
concepts are quite simple, and most mistakes are made by trying to hurry things
up with too-large doses, or trying to adjust two different aspects at once. A
Hot Tub's water is a little harder to maintain than a swimming pool simply
because it's a much smaller volume of water, and that greatly amplifies anything
you do. The difference between pouring a teacup of water into a bucket, and
pouring a bucket of water into a teacup.
On Feb 27, 2:59 pm, email@example.com (Bill) wrote:
Carbonates/bicarbonates, expressed in ppm CaCO3. In outdoor pools
there could be a second minor system, cyanuric acid/cyanuric anions,
and possibly a third, borates/boric acid. We're interested in the
carbonates/bicarbonates system and may apply a pH dependent
"correction factor" if the cyanuric acid concentration is above a
threshold. (The test measures total alkalinity, we just want the CaCO3
Do you have access to you hot tub dealer?
Every time I fill, I take in a sample. They test it for free and give
me a printout telling exactly what to dose and how much, and the time
intervals between doses.
And they don't try to sell me massive amounts of chemicals. Usually
just takes a few TBS of Ph decreaser over a period of several hours.
Note that if you get the PH where you want it, and then add sanitizer, the PH
will no longer be where you want it. Sanitizer will lower the PH, especially if
you have not established proper alkalinity.
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