Swg => MA => low alk

[AllenA]

Hi All,
I recently installed a stenner pump to fight my constant PH rise due to SWG, aeration (waterfall / grotto style) and kids splashing "vigorously", I emphasize, everyday.

I got the stenner pump tuned and PH is sitting nicely at 7.6 as of a few days ago but i also noticed that ALK is at 20 [TA @ 38 with CYA @ 54].

I already added 10 lbs of baking soda and next day TA remained the same. Pump runs 24/7 @1100 RPMs. All tests using newly purchased Lamotte reagents with colorQ. TA reagent expires in 1 year.

The SWG is also new and very oversized and I'm still trying to fine tune it. I already reduced it's output by 5% twice over few days to not exceed target FC for CYA assuming over production will not be protected and just burn off? Is this a good assumption? FC was at 6.42. I'll need the latest numbers of FC after latest change.

I'm assuming that by reducing the SWG it will require less MA which in turn will help not push TA as far down. But if I were to increase CYA to SWG recommended levels, I may need to boost SWG again a bit.

But CSI is good. Should I be worried about such low TA? Pool is crystal clear...

Fc 6.42
Tc 6.42
Ph 7.6
Alk 20
Ch 248
Cya 54
Temp 86 from SWG
Salt 3800 from SWG
Borax 30-50 test strips...

Thanks in advance,
Allen

 

[IceShadow]

Do you have a dropper test you can use to confirm those TA numbers from the ColorQ? If you put baking soda in the pool then the TA is in there. It doesn’t just disappear.

 

[setsailsoon]

Allan,

You can estimate SWG settings using Pool Math. Use "effects of adding" in the menu top left. It's turned out very reliable for me.

Chris

 

[AllenA]

Hey Ice,
I don't unfortunately. I only have old reagents that are expired for Lamotte also. I'll try and see what those give. I also have a doubt that the TA reagnet could be bad that's why I posted the info about it, being new. Wondering if it is possible that new reagents sometimes are off. Btw, I did make the TA measurement twice cause I was really surprised and it came to almost the same result.

I agree that the baking soda must have done something. I wonder if the test itself has a lower cap and the first test was actually even below 20?

So let me ask this though as a general question as I have never been so consistent until now with the stenner pum and MA. As we constantly push PH down, TA is also going down. In general, are most people with SWG then constantly also fighting TA to push it back up? So we trade one problem for another? Or will TA also drift up due to the SWG? I don't believe I ever read that somewhere.

Also, more importantly, if the TA measurement is correct and CSI is fine, is such a low TA still a concern? Other than PH fluctuations?

I'll post another test later tonight.

Hey Chris,
Yeah, thanks I know about it just didn't try the FC tool yet. I'll give it a shot to help fine tune. I got the circupool RJ60+ and with 30% had 5.xx for CYA of 54. I'm hoping the cell will last many many years as my previous LM-24 was just not comparable.

 

[AllenA]

I just performed multiple TA tests. The pool's water gave me 34. My expired reagent gave 99. I didn't do any further with expired reagent.

I then used tap water. A quart of it and only used the new reagent. Pure tap water showed TA of 38. I added 24g of baking soda mixed for 1 min and got TA of 55. Didn't match the expected rise of ~130.
Then I added another 50g, mixed, and got TA of 50. Wow! So the reagent must be bad or could it be that I need to wait longer? I though that once baking soda is dissolved, it should be effective right away. Or maybe my baking soda is bad just kidding! Strange because the lot number is 0070316 which would mean manufactured early March. I now worry that the complete kit is bad.

 

[setsailsoon]

Allen,
`
What test kit are you using? Where did you get it and the reagent? Don't recall anyone having this issue with TA reagent. Let's ask our resident chemistry expert to opine. Matt? @JoyfulNoise .

Chris

 

[AllenA]

Thanks Chris!

It is a Lamotte Colot Q Pro 7 plus. I've had it for many years and it's been very reliable and easy no guessing to use. I believe it is well know here also. I did not buy it from Amazon at the time but just like this:

Amazon.com

I bought the reagents refill from Amazon 2 weeks ago. All of them have good dates and give results to my expectations except TA. But now I wonder...

Amazon.com: Lamotte R-2056 Color-Q Pro 7 Test Reagent Refill Kit: Industrial & Scientific

Buy Lamotte R-2056 Color-Q Pro 7 Test Reagent Refill Kit: Water Test Kits - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Allen

 

[Jimrahbe]

Allen,

Why are you running a pH of 7.6? Most SWCG pools like their pH to be 7.8... The more you try to drive it to 7.6 the lower your TA will drop.

Any pH between 7.8 and 8.0 will be just fine.

I have both the ColorQ and the TF-100... I have three pools and like the ColorQ for its portability and ease of use.. But I only use it to compare today's reading with the last readings.. If I really want to know what an accurate reading is, I use my TF-100... ColorQ also had a recall on their TA reagent.. Took about 3 or 4 months, but they sent me a bottle about a month ago. Don't confuse the ColorQ's digital readout with accuracy.

I already reduced it's output by 5% twice over few days to not exceed target FC for CYA

It is your pool and you can do what you like, but in my mind the key to operating a SWCG pool is to keep your FC at your target or slightly above. There is really no downside to keeping your FC a little high. I never try to keep my FC between the minimum and the target.. I just make sure that I never get close to my minimum.


Thanks,

Jim R.

 

[setsailsoon]

I was late to the party for SWG so I looked for successful ways more experienced use to keep it trouble free. After all, I switched to make pool care easier not harder. Jim's "target or higher" approach has worked well for me also. There are times when chlorine load goes up suddenly with our massive downpours or something else goes wrong. SWG's produce low rates of chlorine production compared to pouring in a gallon. So you stay a little high and it works great. My range is typically 3-8 ppm so I target 6. During light load it floats up to 7 or so. During the massive rains a couple weeks ago it was 3.5. I don't have to mess with changing % power or run time. I leave it be and just watch the FC float within the range.

Chris

 

[AllenA]

Hi Jim,
Ok, I will contact Lamotte about the TA. Mine must also be defective. So, I'll consider the TA reading wrong for now and attempt to get a reading from the pool store for my sanity even if off by some margin while waiting for a replacement which hopefully can be sent soon to me. I'll look into TF-100 for next year but for now I already invested in ColorQ for this year.

As for PH, I am confused...

Pool School states the following:


So I figured that since I can control exactly where it needs to be with constant injection using the stenner, I would keep it at 7.6. I can also tune it to go back to 7.8. But 8.0 does not seem to be recommended by at least the above page. Is 8.0 really ok? And if so, can the above page then be updated?

I also just noticed something strange with the Pool Math app (android version). Plugging in the following suggests CSI of 0:
PH: 7.6, TA: 20, CH: 250, CYA: 54, T: 85, Salt: 3900, BOR: 30

Without changing anything else:
Increase the TA to 30 and CSI becomes -1.19
Increase the TA to 60 and CSI becomes -0.51
Increase the TA to 100 and CSI becomes -0.20

Looks like a bug to me when TA is low. And the reason I mentioned that I had CSI of 0 above. I now hope my TA is within a decent range!

But assuming that this bug only manifests with such low TA, to be close to CSI 0 with all other numbers above, would mean TA would need to be @ 100 and I'd like to ask again...

As we fight off PH to keep it within range, we are adding MA constantly which will also lower TA. For me at the moment, to keep PH @ 7.6, I'm pumping 24 oz of 31.45% MA per day which according to the app lowers PH by 0.4 and TA by 6.3 daily. Won't I end up with a constant low TA and have to now control TA to keep it within range? Is this a common side effect experienced with SWCG owners?

And this very concern is why I am trying to keep FC closer to target. My thought is that by using the SWCG just a bit less, I'd need just a bit less MA, and reduce those side effects just a bit. But maybe my thought above is incorrect somehow?

Chris, you made me realize one thing that I should check for. I have been checking FC during the late evening. But I should also be ensuring that FC does not drop below the min requirement during sunshine when my little bathers need it most. I'd surely want them to be most protected when they are in.

Thanks again guys. I really appreciate your support!
Allen

 

[Jimrahbe]

Allen,,

Instead of a pH of 8.0, think of it as 7.99...

Jim R.

 

[AllenA]

Jim,
I have some calcification on my water line due to previous years when PH drifted up to 8.2 from time to time (my bad) so I want to keep it as low as possible. I already adjusted the stenner pump (MA) to bring it back to 7.8. I'll keep it in mind that 8.0 is acceptable and probably not a big deal.

What are your thoughts on my bigger question, shown once more below? (Regardless of target PH). Imagine that I have 99% control over PH which I believe I approach with the stenner pump and renewed interest in my pool's "health". Would now TA be the variable to keep an eye over and require attention? Or should I expect it to somehow stabilize with such a setup? What are the overall experiences of TFP members with SWCG who like me must control PH which inherently pushes TA down?

"As we fight off PH to keep it within range, we are adding MA constantly which will also lower TA. For me at the moment, to keep PH @ 7.6, I'm pumping 24 oz of 31.45% MA per day which according to the app lowers PH by 0.4 and TA by 6.3 daily. Won't I end up with a constant low TA and have to now control TA to keep it within range?"
Allen

 

[mknauss]

In Scottsdale, you are adding high TA fill water. A lot of it. The SWCG has little to do with the rising pH. It is your fill water TA.

I add acid twice a week during June to mid- September. The evaporation is the highest then, and thus high TA fill water is added continuously.
In April, May, and October, I cover our pool to retain heat. During that time, with minimal evaporation, my pH stays nearly constant. Even with SWCG generating chlorine during that time.

 

[Jimrahbe]

Allen,

I have a hard time even spelling Khemistry... Let's see if we can get Matt to chime in.. Calling @JoyfulNoise ..

Thanks,

Jim R.

 

[JoyfulNoise]

As Marty alluded to, your fill water TA has much more to do with where your TA would like to be then anything else. But, to answer your "khemistry" question - in a closed system, constantly adding acid to maintain a specific pH value in water with carbonate alkalinity will eventually exhaust the carbonate and then cause a sudden crash of pH. But, in reality, your pool is not a closed system and you are constantly outgassing CO2 (causing the pH to rise) as well as adding alkaline fill water. So there is a nearly equilibrium pH that can be found with a bit of fine tuning and measurement. As Jim alluded to, if you target a higher pH, say 7.8, then your acid additions will likely slow down to a point where you will be adding very little to compensate for the incoming, high TA fill water. If your pH target is set too low, then you'll use up your carbonate alkalinity faster than it is replensihed.

Pool water is a complex mix of buffers and PoolMath does a decent job calculating CSI. But that bug you found is a well-known one. You inputted your TA as 20ppm and your CYA as 54ppm (call it 60ppm for ease of computation). At 60ppm CYA, the cyanurate ion adds about (1/3)*[CYA] to your alkalinity, in other words, about 20ppm (it's a bit more complicated than that as there is a temperature dependence but 1/3rd is about good enough). So the TA that you are measuring (assuming your reagents aren't way off) is actually composed mostly of cyanurate alkalinity, there's probably less than 10ppm worth of carbonate alkalinity in the water. Because CSI is a logarithmic function and based on the product of the calcium ion concentration with the carbonate alkalinity, getting close to zero carbonate alkalinity causes the logarithm to blow up mathematically. So PoolMath has this feature (or bug) that will sometimes report the value as zero. It's a coding issue with the functions used on the backend and it's not a simple one to fix. If your pool water parameters are within standard TFP ranges, then the CSI calculation is accurate.

 

[AllenA]

Hi Marty,
I think you just opened my eyes to a major missing variable that I have not been considering all this time; Evaporation vs. fill water. Better not assume that my pool lives in a vacuum . I checked the 2020 Scottsdale report which shows:


Given the above numbers, we can more so confirm that my TA reagent is bad due to my controlled test with tap water (shown above), I'll assume the report above is good enough. And if then SWCG is not the primary culprit for my PH rise then I am actually fighting it due to incoming water which means that I should not expect TA to be pushed down with my above assumptions. That is somehow great news (at the expense of MA of course).

Now, I'm tempted to figure out my evaporation rate! I'm sure my better half will love to hear about the new stuff I'll need to get those numbers .

Jim,
No worries. I'm the type of person who will try to understand the "why" behind everything. I'm old enough to admit that it is sometimes to a good benefit and sometimes not so much.

Gentlemen, thank you much! If Matt still wants to chime in, I am all ears. However, my mind is at ease now so no need to bother him.
BTW, I contacted Lamotte and hopefully will get a speedy response and replacement of my reagent.
Allen

 

[AllenA]

Hey Matt,
We just replied at almost the same. Thank you for adding your input. I can now see how it all works (thanks to Marty and your confirmation thereafter) and will surely consider from now on that fill water is the culprit here as opposed to my original assumptions of SWCG. I believe that I understand it good enough to sleep well tonight and no more concerns over TA drops.
Thanks again,
Allen

 

[AllenA]

So great news! I called Lamotte today and they will send me a replacement reagent that should arrive to me by Friday. Thank you Lamotte!

==>>> A very important thing to note is that TA reagent 7038-G is replaced by 7039-G. Do not buy 7038-G!!! Certain online listings still seem to show 7038-G so beware. Those may also be bundled within kits such as what I bought.

 

[mguzzy]

Pool water is a complex mix of buffers and PoolMath does a decent job calculating CSI. But that bug you found is a well-known one. You inputted your TA as 20ppm and your CYA as 54ppm (call it 60ppm for ease of computation). At 60ppm CYA, the cyanurate ion adds about (1/3)*[CYA] to your alkalinity, in other words, about 20ppm (it's a bit more complicated than that as there is a temperature dependence but 1/3rd is about good enough). So the TA that you are measuring (assuming your reagents aren't way off) is actually composed mostly of cyanurate alkalinity, there's probably less than 10ppm worth of carbonate alkalinity in the water. Because CSI is a logarithmic function and based on the product of the calcium ion concentration with the carbonate alkalinity, getting close to zero carbonate alkalinity causes the logarithm to blow up mathematically. So PoolMath has this feature (or bug) that will sometimes report the value as zero. It's a coding issue with the functions used on the backend and it's not a simple one to fix. If your pool water parameters are within standard TFP ranges, then the CSI calculation is accurate.

I've bookmarked this snippet.. I had always wondered if CYA acted as an alkalinity "upper". Thanks Matt!

 

[AllenA]

Hey @JoyfulNoise,
I do have 2 more Q from my side if you don't mind...
- Most literature related to TA talks only about how it controls PH fluctuations. Given good overall numbers, what if TA was out of range? Any other concerns other than PH fluctuations? That was one of my initial concerns.
- As for TA va CA, I always use Carbonate ALK whenever TA is requested because this is what I always understood must be done (CYA should always be factored in). For example to calculate CSI. But, again, I feel that most literature interchanges TA and CA or maybe expects one or the other but is not always clear. More importantly, the field in PoolMath app itself to calculate CSI is called "Total Alkalinity". So do the PH, TA, etc... adjustment tools. Should we be providing TA or CA? And if CA, should it not be changed to reduce the confusion? I've always wondered about this and maybe others also and others may just not know... Or maybe we should be providing TA? It's definitely a point of confusion!
Allen