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We have had our 500 gal hot tub for 2 years and I keep the water chemistry in good shape as I have learned from reading this forum. But I messed up on last fill and calculated my Calcium Hardness wrong - added too much calcium increase. I realized what I had done and drained about half the water - lesson learned - I should have drained it all. After fighting with water chemistry for about a month - could not keep ph from soaring. I drained half the tub again (it's winter temps here, so I didn't want to drain it all) and cleaned all the jets and the sides of the tub. Again - still fought with water chemistry this last month - ph way too high. I would balance and the next day it would be way too high.

We scored a day above freezing a week and a half ago, so we completely drained the tub and started over. My CH = 120. Next I balanced the TA to 80. Then the ph to 7.6. I left it sit overnight and checked it the next day (wanted to be sure since I have had so many problems) and again my ph is sky high. It is way above 8.0 every day (using Taylor test kit) and I lower it using muratic acid to 7.6 every day. I keep my eye on the TA bringing that back within the 80=100 range using baking soda. The water is crystal clear - we have not sat in it since changing the water. I also have not put in any sanitizer yet.

I called the local spa place to see if they had any insight. I was told to just keep lowering the ph down to like 7.0 every day until it quits rising. Does this sound right to you all?  Anyone else ever have this issue? I am at a loss.

Additionally I am really sensitive to chlorine and bromine. Would the dichlor-then-bleach method be an option for minimal skin issues?


UPDATE! Since posting this I have not made any headway. Everytime I check the ph it is over 8.0  My Taylor test kit shows bright pink - well over 8.0

I have never had issues before and just cannot understand why I am now. Please help? If it were warmer I would drain it, I am worried it may ruin my tub, but it is well below zero here every night.

Edited by Germann
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some quick observations


1.  I wouldn't use muratic acid to lower pH.  use dry acid

2.  you are chasing your own tail by adding baking soda.  this raises pH and then you are adding acid to bring pH back down.  TA is good information to help you balance the water, but thats it -- you shouldn't have to "target" certain TA values for the sake of it.    Acrylic spas can run with a negative saturation index no problem, which means TA can to be low in order to moderate pH spikes.  higher TA numbers will promote pH rise due to agitation.    I run normally at TA=40 and sometimes  30, although I test regularly to make sure I avoid a precipitous drop in pH.  my recommendation is to use dry acid to adjust for pH, let TA fall naturally, but ton't let it go below 30.

3. high pH is irritating and moderates the effectiveness of CL, but you can target a higher pH number like 7.8 and still be ok

4.  sanitize with dichlor.  the reaction is net acidic. 

5.  use a pH buffer such as borates obtained from duda diesel.  this is a wonderful pH buffer especially when you switch to bleach.

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