PH stuck

[HotTub Chris]

I've recently joined the hot tub club and love it. After the first couple months I was ready to change out the water... And now the problem begins.

Now that it's replaced, I cannot get the PH into range. I'm using some PH down that I picked up at Home Depot (after using most of the Sundance branded PH down bottle). The PH just seems to be stuck. What would cause this, and how do I fix it?

CYA = 0 (will this cause PH issues?)
TA = 130
PH = 8.4

 

[Flying Tivo]

What are you using to test your water?

 

[CrystalRiver]

No CYA won't cause problems with pH.

My guess is that your pH is much higher than you think, and the reading you got is simply the top of the scale.

 

[JoyfulNoise]

You should avoid pHDown dry acid. It’s sodium bisulfate. In the short term it presents no problems but it adds sulfates to the water which can cause certain kinds of corrosion to be accelerated, especially attacking the heater element. It is better to use muriatic acid and you can purchase a half strength formulation (15.1% instead of 31.4%) that will emit no fumes.

Your pH will come down as the TA is lowered with each acid addition. 130ppm TA is way too high for a hot tub. You’ll need to get the TA down to 50-60ppm before the pH stabilizes at a lower value.

 

[HotTub Chris]

You should avoid pHDown dry acid. It’s sodium bisulfate. In the short term it presents no problems but it adds sulfates to the water which can cause certain kinds of corrosion to be accelerated, especially attacking the heater element. It is better to use muriatic acid and you can purchase a half strength formulation (15.1% instead of 31.4%) that will emit no fumes.

Your pH will come down as the TA is lowered with each acid addition. 130ppm TA is way too high for a hot tub. You’ll need to get the TA down to 50-60ppm before the pH stabilizes at a lower value.

Is there a brand that you recommend?

 

[gregsfc]

Muriatic acid is basically a commodity; brand shouldn't matter. It should, however be labeled as "muriatic acid". Usually available in hardware stores in paint departments among solvents or cleaners. The full strength stuff, if you go that route, may be near the brick, block or mortar sold as brick and mortar cleaner. It's not a pool water-specific product, but it's the best and least problematic product to use for lowering pH and/or TA in pools and hot tubs.

 

[Mdragger88]

It’s likely higher than 8.4 as stated above so Definitely get u some Muriatic acid & keep dosing to 7.5 using PoolMathuntil u see a change - its in Stock @ your local home depot.

HDX 2 x 1 Gal. Swimming Pool Muriatic Acid (2-Pack) 10014HDX - The Home Depot

The HDX 1 Gal. Swimming Pool Muriatic Acid (2-Pack) is ready for use and does not require mixing. This pH reducer is designed to help prevent scaling caused by calcium-based chlorine and hard water.

www.homedepot.com

Once it tests in that range you can begin the alkalinity lowering process which just involves lowering ph to 7.1 w/ acid (which will lower ta) then aerating (running the jets) until ph rises to 8.0 (this only increases ph not ta) then repeating the cycle until ta is where u want it (50 or 60). My ta starts out about 110 & it takes several cycles of this to get me to a ta of 60 (about 6 or so) the good news is that it’s a fairly quick process in a hot tub. Let your testing be your guide. I use the dichlor then bleach method to accumulate some cya & since dichlor is acidic i take that into account as well using the effects of adding in poolmath How do I use Chlorine in my Spa (or pool)?

 

[HotTub Chris]

It’s likely higher than 8.4 as stated above so Definitely get u some Muriatic acid & keep dosing to 7.5 using PoolMathuntil u see a change - its in Stock @ your local home depot.

HDX 2 x 1 Gal. Swimming Pool Muriatic Acid (2-Pack) 10014HDX - The Home Depot

The HDX 1 Gal. Swimming Pool Muriatic Acid (2-Pack) is ready for use and does not require mixing. This pH reducer is designed to help prevent scaling caused by calcium-based chlorine and hard water.

www.homedepot.com

Once it tests in that range you can begin the alkalinity lowering process which just involves lowering ph to 7.1 w/ acid (which will lower ta) then aerating (running the jets) until ph rises to 8.0 (this only increases ph not ta) then repeating the cycle until ta is where u want it (50 or 60). My ta starts out about 110 & it takes several cycles of this to get me to a ta of 60 (about 6 or so) the good news is that it’s a fairly quick process in a hot tub. Let your testing be your guide. I use the dichlor then bleach method to accumulate some cya & since dichlor is acidic i take that into account as well using the effects of adding in poolmath How do I use Chlorine in my Spa (or pool)?

Thank you for the replies! Last night I added 2 oz of dry acid and got the ph down to 7.4. TA down to about 90 also. That said, I kept the jets turned way down, so it didn't circulate much.
Turns out, the aeration is driving the ph. Almost immediately the ph is back up to 8.1. Im using a digital ph tester as a secondary to the taylor kit.

How do I stabilize at the lower ph? Is it always going to swing like this?

 

[CrystalRiver]

It's the TA combined with aeration driving the pH. Every time you add acid, you lower both pH and TA. Aeration while TA is high raises pH only. So you add acid (lowering both pH and TA), then aerate (raising pH), rinse and repeat until things stabilize around TA 50-60.

 

[pjt]

Thank you for the replies! Last night I added 2 oz of dry acid and got the ph down to 7.4. TA down to about 90 also. That said, I kept the jets turned way down, so it didn't circulate much.
Turns out, the aeration is driving the ph. Almost immediately the ph is back up to 8.1. Im using a digital ph tester as a secondary to the taylor kit.

How do I stabilize at the lower ph? Is it always going to swing like this?

Use muriatic acid, not dry acid. Dry acid has negative side effects, like adding sulfates to your water.