Should I lower the total alkalinity??

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Jun 21, 2018
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Woodbury, MN
New pool owner here and having this website has been a blessing! Thanks to all who have responded to my previous posts.
I have been reading some of the articles here on suggested water balance for SWG pools, specifically with regards to TA.
I understand that TA in the 80-120 range is OK but in the SWG-specific article it recommends keeping it 60-80.
I went to the pool store the other day, and the guy there said my TA was too low at 68 when using the CYAf correction factor (I understand that you don't really use that here but I didn't know it at the time). So he sold me a bunch of alkalinity up and other stuff which I put into the pool as instructed.
Here are yesterday's test results:
FC: 4.5
CC: 0.5
TA: 110
Alkalinity using CYAf correction: 98
pH 7.4
CYA: 40
salinity reading 3200ppm according to the SWG panel

So, based on the water balance for SWG pools article, I added more CYA to target 70-80 range and I am wondering if I should drop the pH and try to lower the TA to target 60-80? I am a little nervous to do this because I don't have any good aerating methods (other than having my kid splash in the pool over the weekend) and am not sure how long it will take for the TA to drop and the PH to climb back up.
Many thanks in advance for your help and input!
 
No need to sweat the TA. Theres' no need to target a specific number. Just add acid when the pH exceeds 7.8.

Your SWG might make the pH rise relatively quickly but as the TA declines, the pH rise should slow down. With where your currently placed don't add anything that will increase your TA that will have you just going in circles.

By the way just trust the results from your K-2006 and forget the pool store.
 
The toughest thing you will find as a new TFP member is cutting the cord with the pool store. Basically they just sold you expensive baking soda to raise TA that didn't need to be raised to begin with. That's how quickly it happens n those places. You have a great test kit, so now you have to trust YOUR readings. When something doesn't meet the TFP Recommended Levels, refer to the Recommended Chemicals page to see what you can use to raise or lower something - if even required. All those links are below in my signature.

So it's good you are increasing the CYA to at least 70 for your SWG. The reason you have to be careful about pH and TA getting high is because a SWG is always generating aeration. Aeration increase pH, and when the pH grows, the potential for scale increase. The first place scale will try to attach is your SWG - and maybe your heater. You can go back and try to lower the TA a little if you like. A lower TA helps to keep the pH from climbing too fast. Pool School - Lower Total Alkalinity
 
First, do your own testing. Second, if you want to use TFP methods, ignore anything you are told by the pool store. In fact, just stay away from pool stores completely.
As far as the TA, the reason we recommend lowering it for SWG pools is that constant rising pH is a issue in salt pools. The lower TA helps to stabilize the pH. It doesn’t reduce the total amount of acid needed, just makes it longer between additions. If you want to bring it down quickly you can use the acid and aeriate method. However, if you just try to maintain a pH in your current range, the TA should come down on its own over time.

If you are confident in the CYA level you posted, it should be raised a bit higher. For a SWG pool in an climate like yours, I would recommend somewhere in the 70-80. But, be very careful not to overshoot since lowering CYA can only be achieved by draining water.
 
Thanks for the replies very helpful. As a follow up to above, I rechecked FC and pH today and it was 0.5 and 7.4, respectively. Yesterday FC was 4.5. Should i be concerned about the precipitous drop? I had the SWG set to 40% pump time and am actively trying to increase the CYA from 40 to 70.
When I got the result above I added liquid chlorine per the pool math recommendation and increased the SWG to 100% pump time for 24 hours, since we are going to have a bunch of little swimmers over tomorrow. But i am wondering if I should be concerned about the 4 point drop in FC in 24 hours. Any thoughts/input appreciated!
 
A 4 pm drop is about the max we would like to see. However in your case you also had little CYA protection for the SWG, so it's understandable. Good thing is you increased the FC right away with bleach. :goodjob: Hopefully you averted any problems there. After the fun-fest tomorrow, check the FC right away and adjust as necessary. You'll get everything dialed-in soon.
 
Update:
retested in late afternoon after multi-hour splash sesh with the kiddos:
FC 4.5
CC 0.5
pH 7.4
Water looks and feels amazing. Will plan to test the CYA next week as it is still dissolving, but hopefully I can get to that 70-80 range as recommended for SWG pools.
You guys are the best!
IMG_3933.jpg
 
Avitron said:
Thanks for the replies very helpful. As a follow up to above, I rechecked FC and pH today and it was 0.5 and 7.4, respectively. Yesterday FC was 4.5. Should i be concerned about the precipitous drop? I had the SWG set to 40% pump time and am actively trying to increase the CYA from 40 to 70.
When I got the result above I added liquid chlorine per the pool math recommendation and increased the SWG to 100% pump time for 24 hours, since we are going to have a bunch of little swimmers over tomorrow. But i am wondering if I should be concerned about the 4 point drop in FC in 24 hours. Any thoughts/input appreciated!
Click to expand...

Regarding dialing in your SWG output % and covering bather load: What's been working for me, and others here, from whom I learned this: don't try to yo-yo your SWG output to cover big swings, or to make up for a really hot day in which you lost a lot of FC to the sun. An SWG is not really capable of that anyway, they are designed to maintain your FC level, not really move it around. Once you get your SWG output set so that your FC remains stable through "regular" days, then leave it alone. If you have a big party coming up, dump in enough liquid chlorine to raise your FC a few points (depending on what you're expecting bather-load-wise). Then test after the party and use liquid chlorine again to bring your pool back up to it's normal level, if you need to. Then the SWG will take over and maintain that level until your next big day. Just like you're learning your SWG settings, you'll eventually get a feel for how much LC to use ahead of a party.

You'll also get a feel for what your % setting should be throughout the year. Lower (or off) in the winter, higher in spring and fall, and highest in summer.

The SWG doesn't necessarily replace entirely the need to stock and use some amount of liquid chlorine, especially if you have an active pool some weeks, and less so in other weeks. If you embrace that, you'll fight with it less.
 

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Dirk, many thanks for your reply! Makes total sense. I have been thinking that the SWG should make life much easier with regards to adding and maintaining adequate FC levels but I am beginning to realize that is indeed not the case. I guess nothing replaced the efficacy of good ol' liquid bleach. I think appreciating and planning for the bather load, and the sunshine, as you say, definitely takes some getting used to.
 
Avitron said:
Dirk, many thanks for your reply! Makes total sense. I have been thinking that the SWG should make life much easier with regards to adding and maintaining adequate FC levels but I am beginning to realize that is indeed not the case. I guess nothing replaced the efficacy of good ol' liquid bleach. I think appreciating and planning for the bather load, and the sunshine, as you say, definitely takes some getting used to.
Click to expand...

I'm still getting used to mine, and what it can or cannot do. So far, it's definitely cut down on manual dosing, like a lot. So I have come to believe all the hype about its convenience factor. I'm still watching it closely, testing every day or two, to see how far I can push it. This year, where I live, we're having some pretty wild temp swings. 80s one week, 100s the next, etc. I'm experimenting to see if I can anticipate a hot week and slide the SWG output up 5% or so, then back down at the end of the hot week. I'm not sure that's necessary yet, but the point is: like all things pool, there's a learning curve, and after having done things for a while, you find what your pool wants and so adjust your MO accordingly. SWG use is no exception to that...
 
Dirk-
I posted some concerns about my SWG on another thread but since I have you here, I'll ask your opinion (FYI: I usually do testing in the early evening, after the last bathers have left the pool). This past weekend we did not have an insane amount of sun but it was hot and muggy (80s Saturday, a little lower Sunday). I had a bunch of kiddos over on both days and the pool was working hard. On Friday evening I started with a FC of 0.5. I added bleach AND I gave the SWG a 100% boost on Friday and got up to 4.5 on Saturday. Gave the SWG another 100% boost Saturday night in anticipation of Sunday. Even more kids, more splashing on Sunday. Retested Sunday evening and FC was down to 2.5. I was actually pleased with this number. My question is, with 100% SWG production for the whole weekend, should I have expected less of a chlorine drop, or is this within the operating expectations of my SWG? My manual says that the 1400 cell adds 1.25 lbs of chlorine per 24 hour period (I'm assuming that is with 100% run time) - according to pool math this is only enough to raise the FC about 0.5ppm for a 33K gallon pool. Am I overthinking it? should I just continue to add bleach as needed and get the feel for the SWG throughout the summer??
 
Sidebar: if your calc's are right, you can see why I mentioned you can't rely on an SWG to swing your FC any great amount. 0.5ppm is nothing on a hot day with kids in the pool! You pretty much have to use LC.

I suppose one could do the math and figure out what the SWG is adding over a given weekend. But I'm not sure that would solve anything for you. Bather load is the wild card, and I can't imagine any way to calculate that. It's one thing to know how much chlorine is going in (SWG + liquid), but how can you use that when you don't know what your FC loss was, or is going to be next time? Even with the exact same amount of kids, for the same number of hours/days... How many times did little Joey pee this time? Next time? How many times did his pals? How many mom's remembered sunscreen? And did they lather 'em up once, or twice? How hard did they play (sweat) each day? Hot hot out was it? Did a few of them spend half the time laying on towels, or were they in the pool the whole time? Etc. So even if you monitor your FC input perfectly, the FC loss is a pretty huge unknown variable.

I think the best you can do is an educated guess, and then buffer the amount of FC to cover "contingencies." I use the TFP FC/CYA chart. I probably have a CYA of 75, I round up to 80. That's a buffer. I ignore the Minimum FC number of 4, and instead use the Target FC number of 6 as my minimum. On a daily basis, I do what I gotta do to make sure my FC never drops below 6. That's a second buffer. That means I keep my FC between 6 and 8. When I'm expecting a crazy hot day, I might bring that up an extra point. Big bather load tomorrow, I might take that up an extra two points, or three if I'm expecting a ton of kids. More buffering. If I experience a big day, then I'll be sure to test that evening, just in case, to be sure my pool doesn't sit overnight with an FC at or below my minimum (which is 6 remember). That way, a lot has to go wrong before my FC gets anywhere near my "real" minimum of 4. Not that you did anything wrong, but for me an FC of 2.5 would be a fail, as it is below both my artificial minimum and my "real" minimum. Sometimes that happens. I expect it will for me. But the TFPC guideline for that is to never let that happen.

My goal it to never have to SLAM. I don't want to goose my FC crazy high to achieve that goal, because it's uncomfortable for me when I do, and it'll just burn off quick anyway, so that means taking a best guess in advance of a big FC day, and doing so diligently and following up after to make sure I got it right. Only by using this MO x-amount of times will I know it works or not, and what, if any, adjustments it needs. So I don't plan to use math for that, but rather experience.

Anyway, that's my brain-dump about it...
 
Dirk-
Thanks. your post really drives home the experience point, which I am clearly lacking (have only been a home/pool owner for 2 weeks!)
Let me ask a follow up question now- I am actively trying to add CYA to bring it up to 70 per TFP recommendations for SWG pools. When I moved in, CYA was undetectable and I got it up to 40 with initial treatment, but noticed I was still losing a lot of chlorine. My question for you is, while the CYA is actively dissolving (and I can't test for it for another 5 days anyway), should I target a FC of around 6 anyway, according to the CYA/FC chart? this morning after the OLCT (thankfully I did NOT lose any FC overnight), I was at 5.5, which is just above the target FC for CYA of 70, even though I'm sure I'm still not at 70 yet since the CYA is still dissolving.
 
I'm not a TFP expert and defer to them for such matters, but I can share my instinct about it. When in doubt, go high for FC. Use the chart at the expected CYA value, to play it safe. It's safe to swim in a pool with FC levels up to SLAM levels. Crazy high FC levels will eventually affect pool equipment, but I believe that is over sustained periods, not a few days while your CYA mixes in. So the only thing you risk by upping FC by a bit, for a bit, is that the un-CYA-protected portion of it might burn off quickly. A small price to pay, IMO, when compared to the potential risk of having to SLAM because you let FC drop too low.

Hopefully this thread activity will catch the attention of someone that knows more about this than me!

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