High pH That will just NOT come down


New member
Oct 14, 2007

Newbie here and I have been reading this forum this last 2 weeks in preparation for filling an inflatable/portable spa that my fella just bought. The TA and pH are both really high and we cannot seem to get it down. Before I say anymore, I have first say that I am in NC and the spa is in Louisiana so I can request chemical readings but I cannot just go test it myself.

This is the first time it has really been filled (we filled it to make sure it all worked but did not treat the water and only kept it for 3 days before draining it and moving it).

We took a sample in to the local Pool and Spa place and they gave us the following analysis:

Total Bromine/Chlorine: .1
pH: 8.4
Total Alkalinity: 212
Total Hardness: 52
CYA: 0
Saturation Index: .7
TDS: 300

We are using SpaTime chemicals from AquChem as they are the most easily accessible in the area. We filled the spa today and the water is still "faucet temperature." Since we are mot planning on using this until next weekend, we just filled the floating brominator will brominating tablets, opened it to the maximum amount, and pout it in the water to start dissolving. Then we started on the water chemistry. Our PLAN was to get pH and TA down and then mess with the hardness. Here is what we actually did :)

We added 1T of pH Down and turned on the bubblers for half and hour. ZERO change in the pH or TA.
We added 2 additional T of pH Down and turned on the bubblers for half and hour. ZERO change in pH or TA.

Now, at this point, I am a bit confused. I was expecting at least the pH would drop SOME but a water test still shows a pH of 8.4. Since the water is SO soft, I thought MAYBE that could be some of our problem so we went ahead and added 1/2 cup of AquaChem calcium hardness increaser. That got our hardness up to 200 where it needs to be but the pH and TA have still not changed.

I do not want to just keep adding chemicals in amounts 3-4 times what is recommended for these readings with no change before I ask to see if there could be something else going on.... something else that all of the instructions are just assuming but do not explicitly state. This is only a 250 gallon spa so I am hesitant to do too much too fast without more experienced guidance. Do any of you have any ideas?

We have just now turned on the heater and it takes 24 hours for it to get warm. Is warm water a prerequisite for getting the water chemistry right?

We are letting it go for 24 hours and are looking at it tomorrow evening and if things have not changed, we will go ahead and add another 1T of pH Down but I would love to have some of your insight....



Mod Squad
TFP Expert
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In The Industry
Apr 1, 2007
Sebring, Florida
Hi, Terri,

Just guessing, but how high does your pH test go? Probably 8.2 is my guess. There's a good chence you pH is/was quite a bit higher.

I have never used "pH down" (i use muriatic acid) so can't advise on dosage but it WILL bring it down and you should continue to add more.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
The pH Down is Sodium Bisulfate (solid crystals -- 93.2% concentration or thereabouts) aka dry acid. In 250 gallons with a TA of 212 and a pH of 8.4 it would take 0.8 fluid ounces, or 1.6 tablespoons, to lower the pH from 8.4 to 7.5, but if you did this while running the bubblers, the pH would tend to rise and instead the net result would be a small decrease in TA to around 200 so not that measurable. As durleigh points out, your pH may have been even higher as the equilibrium pH with a TA of 212 for carbon dioxide in air is a pH of 8.8.

The reason for your high pH in the spa and the tendency for the pH to stay high is the very high TA. A spa with the bubblers and higher temperatures has a lot of aeration and outgasses a lot of carbon dioxide rather quickly. That makes the pH go up. So you do need to keep adding acid to get the TA lower. When you measure the pH at around 8.0 or higher, then add 3.6 tablespoons of pH Down which will lower the pH towards 7.0 and if you run the spa jets, the net result will be a lowering of TA of around 30 ppm. You continue to repeat this process, but add less acid as the TA gets lower. The following tells you roughly how much acid to add at each TA level to go from a pH of 8.0 to 7.0:

TA 210: 3.5 tablespoons
TA 180: 3.0 tablespoons
TA 150: 2.5 tablespoons
TA 130: 2.2 tablespoons
TA 110: 1.9 tablespoons
TA 90: 1.5 tablespoons

If you get your TA below 100, you should find the tendency of the pH to rise be much less and it will take less acid to lower the pH (as you can see above). You can then maintain the pH in the 7.5 to 7.8 range much more easily.



New member
Oct 14, 2007
Thank you for Duraleigh and Richard for your replies.


The pH test we are using supposedly goes up to 8.4 - my fella just says "still bright bright pink". The local spa shop also reported 8.4 in their test results but I do not know what test they are using.

When reading this forum (and other forums on this site as well as other sites), I got the impression that I could add Sodium Bisulfate to get both the pH and TA down - in general, get the pH lower than you need and then when you "bubble it" your TA will drop but your pH will start to climb back up. So my intention was to stick with the single chemical to "do both."

Would you recommend sticking with the SpaTime pH Down dry acid and just get prepared to add a "bunch" (following the guidelines in Richards reply) or would you recommend going to a different process until we get this in range?

Patience is not one of my main personality characteristics and normally I would just keep adding the pH Down, wresting the pH to the ground. But this is a spa where humans will be bathing so I may be over cautious.



TFP Expert
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May 7, 2007
Silver Spring, MD
You will need to use quite a bit of PH Down, but not all at once. Bring PH down to around 7.0, the run the bubbles for a while and the PH will come right back up. Each time through that cycle the TA will go down. Eventually the TA will get low enough that the PH won't go right back up when the bubbles are on.