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High Ph After Refill


Ohio Tubber

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Hi all, I am relatively new to owning a spa (8 months) and I've been having issues with high ph readings after my 2 water changes. During the initial 4 months after getting the spa I really did not have any water issues and all the numbers seemed stable and needed only minor adjustments. After my first water change I had very high ph readings (8.0+) and I spent a few weeks chasing the ph up and down. I attributed this to me being a new owner and probably doing something wrong. Thankfully I found this forum and all of you very knowledgeable people. I spent a lot of time reading the posts trying to get a good understanding of how the chemistry works and I saw a post encouraging the use of Gentle Spa to maintain the ph so I decided to try it to see if the initial high ph readings would be eliminated.

Here are the readings from my current refill after the tub was filled (no chems added)using a Taylor drop test.

The tub is a Hot Springs Vangaurd 400 gallon with an ozonator and a 24 hr. circ pump.

Alk: 100

ph: 7.4

Calcium: 130

I added 10 oz of Gentle Spa per the instructions, added the Nature2 cartridge and then added 2.4 table spoons of dichlor to activate the cartridge.

Here are the readings after the tub came up to temp (102 F).

pH was 8.0+

alk was 110

What would cause the pH to jump up that High? The Taylor instructions say that the pH readings are protected from high chlorine levels so I don't think the initial superchlorination required for the Nature2 is causing the high readings. Could the Gentle Spa cause this, even though I had a similiar problem after my first water change and did not use it? I am not sure what is causing the pH to jump so high and I really need some advice, I don't want to keep chasing the pH again.

Thanks

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Your Chlorine levels are high. High chlorine levels interfere with the pH test and cause a false high reading. Wait for the level to drop and retest.

The Taylor pH test is fine up to about 10 ppm but your 2.5 (I assume that is what you meant) tbls. of dichlor in a 400 gal. spa (which probably only had about 380 actual gallons in it) brought your FC higher than 10 ppm.

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Hi again, I finally got the pH to remain stable after following Nitro's write up on lowering Total Alkalinity, great instructions Thanks!!!

Here are the numbers now:

TA= 60

pH=7.6

It took alot more dry acid to lower it than I would have expected considering I started at 7.4 out of the tap. So i have a few questions; what would cause the jump in the pH when I started at a normal value like 7.4? I'm thinking it had to be the Gentle Spa but isn't that supposed to be pH neutral? Also, is there a way to check on the borate level in the spa? I noticed that that value of borates in the tub affects The Pool Calculator's recommendations on how much dry acid to use and I can't seem to find out how much the borate level rises with adding 10 oz of Gentle Spa.

Thanks!

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Gentle Spa is mostly boric acid so just use that in The Pool Calculator though you are right that it doesn't list Boric Acid in the "Effects of Adding Chemicals" section. 50 ppm Borates in 350 gallons raises the borates (ppm Boron) by 13.4 ounces weight (about 14.9 ounces volume) so if this is the size of your spa, then 10 ounces weight raises the borates by around 37 ppm.

The Gentle Spa would be nearly pH neutral. The jump in pH was most likely due to the higher TA level, especially if you had the jets running. Aeration makes the pH rise even faster. When you add acid to lower the TA, the low pH also accelerates the outgassing of carbon dioxide and therefore the pH rise -- that's how the TA lowering procedure works. Yes, if you do the TA lowering procedure after you've added boric acid, then it takes more acid to lower the pH and it takes more aeration to make the pH rise.

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