Going Crazy with ph/TA

[Windebrook]

Hi all. I just cannot believe noone else has ever had this problem. I have battled and searched for years for an answer on web but never came across anything to help or explain why. I posted once before a few years ago about this topic in swimming pools (didn't know then where to post for spas). At that time the PH held ok at TA of 50. Well that didn't last, didn't reopen spa again til now. So....here we go again. (fyi - I also have same problem with fish tank and can only have fish that can tolerate high ph in it. Pool seems to maintain - probably because is mostly rain and snow melt). So...I have spent a better part of a week trying to balance ph and TA (dry acid and Na bicarb). When I got ph balanced (7.6), the TA went to 40-45. When I raised ta to 115, ph went off chart (TF test kit). So i lowered ph gradually again with dry product, ta bottomed out. So then I gradually raised TA to 170 and commenced using muriatic acid over past 24 hours to get ph down slowly. So ph is still high (8.2+ but coming down) and ta is now at 100...see where I am headed again!? Help, I am going bald! Thanks in advance for any info/assistance. Details below.

Bev in MA


Saratoga spa - Adelphi
Well water - ph 7.6 out of tap, 8.2-8.4 after sitting 24 hours, TA within normal, CA low
Nature 2 w/dichlor as needed and MPS and ozonator

FC - 0.5
CC - 0.5 (mps?)
ph - 8.2
TA - 100
Ca - 200
temp - 100

 

[Richard320]

Why do you want the TA so high? High TA leads to pH rise, especially when it gets a lot of aeration, which a spa/hot tub will do. Take a look at Pool Math and scroll waaaaaay down and set it up using SPA. You'll see the recommended TA is much much lower than you've been targeting.

While you're playing with that, check out the effects of adding chemicals. Dichlor is acidic and affects pH and TA.

The recommended levels are just that: recommended. They are not absolutes. Some people have water so hard that straight from the tap they're already almost at the max for CH. Every system has its own personality and you just need to find the sweet spot. If the pH will hold steady with 50 TA, then run it at 50. In and of itself, high or low TA has no adverse health effects; it's just baking soda! Its function is as a buffer to stabilize wild pH swings. If you can stabilize pH without adding baking soda, then don't waste money adding it.

 

[Windebrook]

Hi Richard,

Thanks for response. I know, sounds bizarre to raise TA so high right? Guess I was hoping that as I brought ph down that TA would fall into good range. I was trying to get ph in range and get a ta of at least 70, but that has been impossible to do. I am not sure I can even get a ta of 50 this time around. I will balance out ph then at whatever TA wants to do and see what happens. I will let you know. Out of curiosity, any ideas on why well water would stay so stubbornly high on ph even when treated? And why we get lime scale even though CA tests out on low side? Thanks again.

Bev in MA

 

[Windebrook]

PS.

Thanks for pointing me to bottom of pool calc page. Guess I was trying to shoot for wrong values. Will let you know how I do. Thanks again

Bev in MA

 

[Richard320]

Hi Richard,

Thanks for response. I know, sounds bizarre to raise TA so high right? Guess I was hoping that as I brought ph down that TA would fall into good range. I was trying to get ph in range and get a ta of at least 70, but that has been impossible to do. I am not sure I can even get a ta of 50 this time around. I will balance out ph then at whatever TA wants to do and see what happens. I will let you know. Out of curiosity, any ideas on why well water would stay so stubbornly high on ph even when treated? And why we get lime scale even though CA tests out on low side? Thanks again.

Bev in MA

Just keep knocking pH down into range with acid (Note that MPS has sulfur in it. I don;t know if it smells when it build up, just mentioning it) and the TA will lower. Eventually, you'll notice you were able to go longer periods between additions of acid. That's the sweet spot for your TA level.

As for scale, have you looked up Calcium Saturation Index - It's the CSI on the calculator? High temperatures raise CSI a LOT. So does high TA. So does high pH. Those seem to have more effect on whether or not the Calcium starts scaling than the actual CH level. Play with the values a little. Fill in all the blanks and see what effect raising TA or lowering it has on CSI. Try all the parameters. See for yourself. CSI above .6 is almost a sure thing you'll get scale.

 

[chem geek]

What are you using to disinfect your spa? The type of product used matters since some are net acidic while others are closer to pH neutral. When using a hypochlorite source of chlorine, such as bleach, you'll want the TA low at around 50 ppm, but you should also use 50 ppm Borates (usually from boric acid) to have more pH stability. See Using Chlorine in a Spa.

 

[Windebrook]

Ok, so one week later and I finally have ph within range. Adding 1 tsp muriatic acid/day, and 1 tbsp MPS/day; also 1 tbsp MPS after use (infrequent). Ph 7.6 yesterday (didn't add any acid) and about 7.4 today. So tested TA - 30. Pool calc page called for 2 tbsp b.soda for TA to 50. Chemical additon calc. said this should not raise ph much at all but just to be cautious I decided to add 1 tbsp b. soda. Now PH 7.6 and TA 40-45. Afraid to add any more b. soda as I know ph will go too high again. Am going to let it ride at this and check tomorrow to see what happens. Is TA 40 ok? Will update soon. Thank you everyone for the assist, and still open to any advice.


bev


Saratoga spa - Adelphi
Well water chem - ph 7.6 out of tap, 8.2-8.4 after sitting 24 hours, TA 70-90, CA 100-120
Nature 2 w/dichlor as needed and MPS and ozonator

 

[chem geek]

TA 40 ppm is OK though we usually say not to go below 50 ppm to be a little on the safe side just to make sure you don't exhaust your TA. This is especially true if you use any net acidic chemicals such as the MPS you have been using. When the TA is set this low and you plan on using bleach, then we usually recommend the use of 50 ppm Borates (usually from boric acid) for additional pH buffering. Though the borates may not reduce the amount of acid you need to add over time, it will slow down the rate of pH rise so that you don't need to add acid as frequently (i.e. you add more when you add it, but you add it less frequently).

Have you every tried using 50 ppm borates? It sounds like you should be doing that. Get some boric acid to add to the spa and you can use Pool Calc to calculate dosing.