Is my PH logic correct

[Jtate84]

Hi there,

I have a 400 gal Sundance Chelsea SWG. I'm pretty good with chemicals but am experiencing a very frequent need to add MA to lower PH. Between uses, the PH consistently creeps up to 7.8-8.0. Am I correct in thinking that I should lower my TA to around 60 to slow the PH increasing? I've always thought that TA was a PH buffer (meaning higher would prevent it moving), but read in the sticky that TA should be no lower than 50.

FC: 3.0
PH: 7.6 target, fighting it every other day with MA
TA: 80
CH: 165
CYA: ~30, probably a bit lower
Borates: ~40

 

[Texas Splash]

Hello and welcome to TFP! With the SWG, you do have some room to lower TA a bit more if you think it will help keep the pH a bit more stable. We always refer to the TFP Pool School - Recommended Levels chart for those levels. It's the opposite of what you mentioned above however - the "lower" TA "should" help prevent the pH from rising as fast. Of course aeration and even an SWG can cause pH to climb a little faster as well, so keep that in mind. Lastly, some pools/spas simply like a pH to sit at about 7.8. So you might find yours likes that higher end of the scale. Fighting it can sometimes be fruitless. Hope that helps.

 

[JoyfulNoise]

Total Alkalinity represents the total concentration of chemical species in the water that can accept a hydrogen ion. Total alkalinity is made of many different species. In pool and hot tub water (at least hot tubs that follow the dichlor/bleach method), the main components of TA are carbonates and cyanurates. The largest component of TA in pool & spa water will be carbonates, mostly as bicarbonate anion (HCO3-). Bicarbonate does buffer pH BUT it also contributes to increasing pH because bicarbonate will chemically transform into aqueous CO2 and, in the process, consume a hydrogen ion. It is because carbonates are not permanent in water like borates or cyanurates that they both buffer pH and change pH. Borates can not outgas and neither can cyanurates so they have a fixed buffering capacity that is based on their concentration. CO2 can outgas from water and so bicarbonate levels can change over time.

This is why the sticky in the sub-forum recommends lowering TA to 50ppm and then adding 50ppm borates - the borates act as a buffer against rising pH and, because they are permanent, there is no change in their effect on pH over time.

 

[Dodger]

Total Alkalinity is represents the total concentration of chemical species in the water that can accept a hydrogen ion. Total alkalinity is made of many different species. In pool and hot tub water (at least hot tubs that follow the dichlor/bleach method), the main components of TA are carbonates and cyanurates. The largest component of TA in pool & spa water will be carbonates, mostly as bicarbonate anion (HCO3-). Bicarbonate does buffer pH BUT it also contributes to increasing pH because bicarbonate will chemically transform into aqueous CO2 and, in the process, consume a hydrogen ion. It is because carbonates are not permanent in water like borates or cyanurates that they both buffer pH and change pH. Borates can not be outgasses and neither can cyanurates so they have a fixed buffering capacity that is based on their concentration. CO2 can outgas from water and so bicarbonate levels can change over time.

This is why the sticky in the sub-forum recommends lowering TA to 50ppm and then adding 50ppm borates - the borates act as a buffer against rising pH and, because they are permanent, there is no change in their effect on pH over time.

Matt, I wish you were my chemistry teacher many years ago at Berkeley!

 

[Oly]

The pH in my spa creeps up as well and is due primarily to my fill water which has a TA of 175 ppm, primarily sodium bicarbonate. I test the pH daily usually while I'm using the spa. I simply add 10 mls of muratic acid (after I get out) when my pH gets above 7.6. This happens about every 7 days depending on how much fill water I use to keep my pH in the zone, my spa is only 250 gallons and is a stand alone fiberglass unit. My main objective to maintaining my pH in the mid to low 7s is to increase the lifespan of my pump seals. A high pH will cause the pump seals to fail and inevitably begin seeping water into the bearings. As this happens pump noise increases as the bearings begin to drag eventually requiring removal and replacement. I could reduce the TA in one shot at startup but with frequent use requiring constant topping off with tap water high in TA I find it better to watch and the adjust the pH as I go. A new motor and pump for my unit runs just over $100 and working in that confined space is no fun, besides having my spa up and running is an important part of my physical and mental health on these cold winter days.

 

[Jtate84]

Perfect thanks. My TA is about at 70 now so I’ll probably try to drive it to 60 over time.

I tested again for borates and am a little low. My spa dealer gave me a product called “silky smooth” which allegedly “locks in ph” but I’m not clear what it actually is as there are no chemicals listed. They said it was borates but also said to just dump the whole bottle in. I’m skeptical they know anything as they originally tried to tell me my Ph would drop over time... any idea what that stuff is?

 

[JoyfulNoise]

Perfect thanks. My TA is about at 70 now so I’ll probably try to drive it to 60 over time.

I tested again for borates and am a little low. My spa dealer gave me a product called “silky smooth” which allegedly “locks in ph” but I’m not clear what it actually is as there are no chemicals listed. They said it was borates but also said to just dump the whole bottle in. I’m skeptical they know anything as they originally tried to tell me my Ph would drop over time... any idea what that stuff is?

Do you have a bottle? Do you know who manufactures it?

 

[Jtate84]

Yeah I can see how that would’ve been helpful the first one around.

its marketed as New England Spas “silky smooth”.