TA numbers?

[steve771]

It seems that most numbers have a fairly "tight" range.  That is to say, the recommended range is pretty close, no matter who you talk to or what you read.

However, I've noticed quite a fluctuation in what you hear/read about Total Alkalinity.  Anywhere from 30-60 to 80-120 to up to 150.  This seems like quite a difference.  Can anyone explain this?  

[windsurfdog]

Can't explain it but if your TA is anywhere in that range and the pH is just right, leave it alone.  If the pH needs adjustment up, then consider TA and whether to use sodium bicarbonate or sodium carbonate....and only try to hit your pH number.  If your pH needs to be adjusted down, use enough acid, either dry or muriatic, to get the pH correct.  Also, if you are using dichlor alone or dichlor with straight MPS, be aware that your pH should drop gradually over time possibly not needing a downward adjustment if pH is a little high.....

[steve771]

You mean anywhere in "that" range of 30 to 150?    Ok, well, I guess I just need to balance my pH then.  Thanks!

[Steve]

30 -150 might be a bit a of a stretch.

80 -150ppm would be far more accurate. Any TA reading below 80 will have a tendancy to lower your pH continually. Aim for a 100ppm reading and then balance pH. Never balance pH prior to the TA.

Steve

[windsurfdog]

You mean anywhere in "that" range of 30 to 150?

30 may be a little low and 150 may be a little high but generally, yes.  I did a fill on Thanksgiving day with these readings:
CH--170
TA--170
pH--7.3
I did nothing but sanitize and soak.
The next day after the fill, sanitize and a couple of soaks I had these:
CH--170
TA--170
pH--8.0
I resisted the urge to add dry acid to bring both TA and pH down, not wanting to foul the beautiful and foam-free water.  I figured that regular dichlor use and shocking with either dichlor or pure MPS would bring the pH down gradually.  After shocking and another week's use, I had these:
CH--170
TA--160
pH--7.7
And just this past weekend after a couple of more weeks of sanitizing, shocking and soaking, I read these:
CH--160
TA--110
pH--7.6
The water has remained much clearer, I'm experiencing no scum whatsoever, and I'm finding that small puddles of water on the rim of the tub and on the control panel leave almost no water marks at all....an indication of not much TDS in solution, I think.  So I guess less has turned out definitely better for me.  Good luck with yours....

[stuart]

30 -150 might be a bit a of a stretch.

80 -150ppm would be far more accurate. Any TA reading below 80 will have a tendancy to lower your pH continually. Aim for a 100ppm reading and then balance pH. Never balance pH prior to the TA.

Steve

Can't add to that expert advice!

[steve771]

After I did my fill, my TA was 110 (and has held about there).  I just wondered about the wild ranges of TA.  AND my pH was spot on at 7.4, so I thought I was golden.  BUT a couple days later, my pH shot up to the 8 range.     I would like to just let it go as you suggest, but I did add a little ph down, as 8+ seemed way out of whack to me.  It is now about 7.8, so I'll let it go for a bit and see how it progresses.  Thanks guys.

[poolboy34]

are you by chance using Nature 2 or Spa Frog?

[HotTubMan]

I understand WSD's desire to add less and "leave it alone", threrfore keeping TDS down.

IMO, keeping the pH + TA high for weeks is a mistake. One must consider the effect on the spa & spa equipment. High pH &/ TA means the water is more likely to allow scale formation. This will result in more calcium build everywhere, especially the heater. As little as 1millimetre of calcium on your heater element can reduce efficiency signifigantly.

I would suggest balancing weekly with these parameters:
TA 80-120
pH 7.4-7.6
CH 150-200

As far a when to adjust TA, Steve had it right. Below 80, TA seems to errode pH and can also allow pH bounce. I get my TA up 120 and let it go until 80-85, then I boost it back up to 120. I dont wait until it drops below 80 because it makes a lot more work.

My 2.4 cents

HTM

[windsurfdog]

Steve,

With the pH of dichlor being about 7.0 and the pH of unbuffered MPS being lower than that (around 6.4, 6.5 maybe?), I've been very pleased with the results so far.  Fortunately, my pH never exceeded 8.0--at least when it was measured.  I think with the great comments and opinions that are offered in this thread, you will find a comfort zone that works for you just as I have.

Oh, and one more thing, for those that put stock into the Saturation Index, the most extreme of the readings I detailed in the previous post was only about +.2 outside of the -.3 to +.3 acceptable range using the Taylor Test Kit Watergram.  The last, most recent readings were within +.2 of perfect according to that method so I feel comfortable with the balance and its effects upon the equipment.

Good luck!

[poolboy34]

MPS has a pH of 2.3, that's why it tends to bring down your alk over time.

[steve771]

are you by chance using Nature 2 or Spa Frog?

Nope, just an alternating dichlor/MPS shock with a teaspoon of dichlor every day.

Anyone have any ideas when I first filled I had a 7.4 pH, but it has zoomed up to eight?  I shocked with MPS and used a teaspoon of dichlor and that was it.  ZOOM!

[poolboy34]

how many jets does your spa have???  Jets introduce air into the water, which raises the pH.

[steve771]

Ah, around 46-50 jets (I could go look up the exact number, but I just did a lazy count at the tub).  I thought that was around the norm?  

[windsurfdog]

Steve,

Here's my latest numbers as of this a.m.:
CH--150
TA--100
pH--7.6
Also, I shocked  with straight MPS today and expect the pH to continue gradually dropping.  I'm not planning to adjust with sodium (bi)carbonate until pH remains around +-7.2 for a week or so in order to counteract any possible calcium deposit that HTM warned about in an earlier post.  So far, zero foam, zero scum and crystal water.