Fastest way to balance TA and PH after refill? My process takes multiple days

[duganderson]

It takes multiple days to get my PH low enough after a refill in my 400 G. tub with city water (Minneapolis, MN). I tend to need about 12-16 OZ of dry acid. I use Taylor K2006 to determine acid demand to ph of 7.2, add dry acid to get to 7.2, retest, repeat.

How long after adding dry acid can I likely retest and add more?

Would switching to Muriatic Acid or Acid Magic go faster?

Any tips, links, etc. appreciated. Thank you! Doug

 

[kellyfair]

I use MA, when needed, but I’m fortunate enough to hardly ever need to adjust ph.

 

[irekz]

I do it in around 2 hours.

My hot tub is around 760l and water is hard (250 ppm of TA).
Overall I need to add around 350g (12oz) of dry acid to drop it to around 80ppm.
This takes me around 2 hours to complete. Using pool math I calculated that I need to add 70g of dry acid to drop ph from 7.8 to 7.0 (tested to confirm). Then I drop acid and run all jets with air. After 15 minutes ph would be back to 7.8 so I repeat the process 5 times - after 3rd drop it takes around 20minutes for ph to rise. Last addition I wait even longer (30 minutes to be sure) and smaller ammount not to overshoot.

Important point: aeration with jets is what allows this process to be quick.
By adding acid - we trigger a reaction where acid combines with bicarbonates to create: salt, water and CO2.
CO2 in water is what we read as low ph (carbonic acid) - but aeration will allow for CO2 to outgass, ph to rise, and to be able to add more acid quickly. Make sure to keep the cover open for the duration as well.

If ph is good, then I add 50ppm borates - and that job done.
Hope this helps.

 

[duganderson]

Thank you VERY much! Your description was very clear and this sounds like a GREAT process. Thanks again!!!

 

[duganderson]

I've read some things that suggest that after a fill of new water, you slowly add Muriatic Acid in 15-30 minute increments until PH quits rising above 7.8 after aeration. The things I've read suggest that you should measure your alkalinity at that point and that is the Alk that you should try to maintain for your tub. Is this true? OR is there a set number that makes more sense for hot tub alkalinity.

My tub is a 400G tub in MN typically at 102 degrees with Nature2, CYA at 30, MPS after every soak and weekly shocks with bleach. I ensure my pipes get flushed at least every 4 months with Ahh-Some (just learned about this and it is AMAZING compared to other flushes!)

 

[ajw22]

I've read some things that suggest that after a fill of new water, you slowly add Muriatic Acid in 15-30 minute increments until PH quits rising above 7.8 after aeration.

Where did you read that? I don't think it was here on TFP?

When the pH stops rising after aeration it means your TA is very low. You don't want your TA that low.

 

[duganderson]

I recently refilled my 400 g hot tub after two Ahh-Some flushes. I recently added some water due to evaporation and I"m having a hard time to get the PH to drop. My alk is 110. The acid demand test on my Taylor 2006 keeps saying I need to add about an once of muriatic acid but it does not seem to drop. I've added about an once several times and the acid demand test keeps saying about the same thing.

Isn't the acid demand test to determine how much acid you need to drop the PH to level you're wanting?

Any suggestions?

Thank you, Doug

P.S. As a fairly new hot tub owner, this forum has been SOOOOOO valuable. Thank you! Special thanks to ChemGeek and the many other folks who share their deep knowledge.

 

[Newdude]

Hey again Dug !! Are you sure of the MA strength ? There are many options and it can make a big difference if you need to add twice as much. MA should do its thing almost instantly.

Other than that all I can advise is to take your time with your 5 drops so you aren’t adding the equivalent of 7 drops in haste. It’s too easy to go 1.....2......345 good enough.

 

[Mdragger88]

Nothing against the acid demand test but I just add the amount of MA PoolMath tells me to lower to 7.1 & then aerate back up to 8.0 then lower back to 7.1 & so on - every couple of cycles i check my ta. My ta starts at about 120 & i get it to down to 50 in a few hours or so in my spa. Then aerate to about 7.4 ph & add boric acid. After this I usually don’t have to adjust ph but a few times between drain/refills. As stated above be sure you are selecting the correct strength of ma in poolmath.

 

[duganderson]

Thanks for the thoughts. I confirmed the strength of MA and am careful about testing but I agree that I'll probably stop using acid demand test. I used basically the same process as Mdragger88 and will just keep doing that. Thanks!