pH is high but Alkalinity is low

[solo]

I had nice stable water chemistry for months, then came time to drain and refill.

It doesn't look bad:

Calcium= 280
pH= 7.8
TA = 61

But I would prefer the pH to be a tad lower and the TA to be a tad higher.

What should I do?

[soak-king]

I am far from being a chem expert and hopefully a few will chime in, but, in my limited experience you always address Alk first and then fine tune your PH afte Alk is in range.

Hope this helps.

[hottubdan]

Soak King is correct.

Raise TA.

Then drop pH.

[Chad]

I had nice stable water chemistry for months, then came time to drain and refill.

It doesn't look bad:

Calcium= 280
pH= 7.8
TA = 61

But I would prefer the pH to be a tad lower and the TA to be a tad higher.

What should I do?

If those readings are what you got right after your refill  w/o adding anything, I'd recommend just letting it be for a few days and see where your pH and alk go. Typically, a low alkalinity will draw down your pH.

[sonofsail]

Wait a few days, as Chad suggested. If the pH is still high, add a little pH down (or dilute muriatic acid) to lower pH to 7.0 - 7.2.  Then add  some baking soda (sodium bicarbonate) to raise TA.  This should also pick up the pH a little.  Easy does it when adjusting chemicals, you can always add more, but once its in there you can't easily get it out.

[TubsAndCues]

There's no reason to wait.  In fact, the longer you wait the more potential damage you can do.  As your total alkalinity drops on you, your pH will drop as well, but you could very well see a drastic drop in pH.  

If you allow your pH to stay low over a period of time, a few things will happen:

1.  Corrosion of the surfaces and equipment.  Allowing your pH to stay acidic will drastically shorten the life of you tub.
2.  Chlorine leaves the water prematurely with a pH below 7.2
3.  Skin, eye and possibly breathing irritation.
4.  Degradation of your cover.

And for the record, if you are adjusting levels in your tub, the proper order is this:
1.  Total alkalinity
2.  pH
3.  Calcium hardness
4.  Sanitizer (or shock)

Hope this helps.

[tony]

I also agree with Chad.  In this case the pH is on the high side of normal and TA is slightly low, but not too low.  The lower TA should draw the pH down at which time you can raise both with a little baking soda.  Just keep an eye on pH to be sure it doesn't drift out of the recommended 7.2-7.8.

[magoomba]

Is there an ideal time to test for these readings?  Meaning, should they be tested before adding chlorine, after adding chlorine; before using the tub, after using the tub; etc.?  I use a digital tester that someone recommended here and I find the pH, Alk and Cl levels change before and after adding chlorine and before and after using the tub (I use MPS 10 mins before each soak).  Given this, which reading is the "accurate" one, or should it always be within the recommended ranges, regardless of when tested?
Thanks.

[windsurfdog]

I never test more than once a week.  Testing too often causes water micromanagement...definitely not a good thing.  Normally I soak with a cup of coffee first thing on Saturday morning and then test after soaking before my normal apres-soak chlorine addition...works for me... 8-)

[Steve]

Being that your pH is in range, I too would suggest leaving it for a few days and retesting. There is no concern of damage or skin irritation considering that the water is NOT acidic at this point. A low TA will tend to draw down pH so you do need to keep an eye on it though. Chances are that your pH will not stabilize until you have a TA which is in range (80-120ppm). Adjust TA and use small doses of pH +/- as to not effect the TA over the period of 2 or 3 days.

I will however totally disagree with sonofsail!!

Muriatic acid should IN NO WAY be used to adjust pH even if diluted.

This product is ONLY used for EXTREME cases of high TA (500ppm+) and should not be used in a spa otherwise!! It is designed to knock out high TA and not for minor adjustments of pH.

[windsurfdog]

Muriatic acid should IN NO WAY be used to adjust pH even if diluted.

This product is ONLY used for EXTREME cases of high TA (500ppm+) and should not be used in a spa otherwise!! It is designed to knock out high TA and not for minor adjustments of pH.

Not to mention how much harder it is to handle and store muriatic acid (liquid) compared to dry acid (powder)... 8-)

[Steve]

Not to mention how much harder it is to handle and store muriatic acid (liquid) compared to dry acid (powder)... 8-)

Zactly! That too!  

[104 degrees]

Soak King is correct.

Raise TA.

Then drop pH.

This is what i do. Hows the family and Jacuzzi been Solo??

[solo]

The hot tub has been great.  No problems whatsoever.  The fam has been doing well too, though my health is still not quite right.  Gettign better, but not quiter there.

But I feel good enough that I don't feel like I must soak every day.  Down to 2-3 soaks per week.