Salt and Chlorine

Sollace

Gold Supporter
Aug 16, 2020
533
Bryan TX
I wasn't sure if this should go under 'balancing water' or under SWG equipment. . . . Or maybe there's a SWG balancing thread. . .

Hubby brought up a point on the salt conversion to chlorine (salt water generator). From what I read on various threads on this forum, with salt water pools, the salt level stays the same, doesn't fluctuate. He said for the chlorine to be converted, salt is used therefore the salt level in the pool goes down. Is he right?
 

Sollace

Gold Supporter
Aug 16, 2020
533
Bryan TX
That's what I thought! I mean every single post about salt water pools say their salt levels haven't changed from year to year. Not unless they dump water.

Well we need to dump water on our month old pool. Our 'expert' dumped salt in, never told us how much or what was used. Hubby got outside to check on him a bit late, just to help brush. . . .And I'm not going to post numbers and such because I can't believe what hubby remembers and what the 'expert' won't say.

The Taylor K-1766 (salt) kit, after a 72 hour wait says our salt is at 4400 ppm. (22 drops at 10ml) Yes, I redid it. Chlorine is out the roof,
probably due to the SWG was running for five hours until I knew about it and we shut it off. Talking about breaking in the pool !!

Before salt:
TA 100
Chlorine 3
PH 7.2
CH 300

Night after salt added
PH 7.8
Chlorine 5
Salt 4400
 

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
3,873
Stuart/FL
Pool Size
12800
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-30 Plus
The only time you lose salt is when you pump water out of the pool or it overflows after heavy rain storms. We get a lot of those in S Florida about half the year. I just check the salt with a 1766 test kit every fourth or so monsoon rain and I use the full range recommended for my unit to reduce the number of salt additions. Also, salt is pretty cheap at big box stores.
 
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mgtfp

Bronze Supporter
Mar 5, 2020
973
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
SWG turns salt (chloride) into chlorine. UV light and all the stuff that chlorine kills or oxidizes in your pool turn chlorine back into chloride (salt). It's a cycle. There might be a tiny amount of chlorine gas that doesn't dissolve fast enough in the water after being created by the SWG and escapes as gas into the atmosphere, but that really shouldn't be noticeable compared to losses due to splash-out or backwashing.
 

mguzzy

Gold Supporter
Hubby brought up a point on the salt conversion to chlorine (salt water generator). From what I read on various threads on this forum, with salt water pools, the salt level stays the same, doesn't fluctuate. He said for the chlorine to be converted, salt is used therefore the salt level in the pool goes down. Is he right?
Technically hubby is right. So buy him a beer. And as @mgtfp says its a cycle.. the salt is converted to chlorine and then degrades back to salt. BUT, the amount of salt that decreases as it is converted to CL is at such a low amount that I doubt a k1766 is sensitive enough to pickup the effect of the conversion. That is my gut feeling without actually doing the stoichiometry.. So you'll have to excuse me if I try not to relive high school chemistry to figure it out.

But I can tell you this.. Hayward T-cells work better on the lower end of their operating salinity spectrum. It helps protect the controller. So if you have 4400 and you need to get to 3000 ppm salinity you are looking at draining a bit more than a quarter of your pools volume. And when you do that you will be reducing your CYA levels too... so measure both after you refill.
 
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mgtfp

Bronze Supporter
Mar 5, 2020
973
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
BUT, the amount of salt that decreases as it is converted to CL is at such a low amount that I doubt a k1766 is sensitive enough to pickup the effect of the conversion.

I agree. The test accuracy of the salt test is 200ppm, and you are talking about a few ppm (like 2 or 3, or something like that) worth of salt per day being turned into chlorine and back again. No way to ever notice that in your testing.
 

Bperry

Gold Supporter
Aug 20, 2020
295
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
5 ppm of Cl is not high. Make sure you follow the SWG levels on this FC/CYA Chart. You have not tested for CYA or have not let us know. Please do, so you know how much chlorine level you need.

yea, chlorine level doesn’t look high. Salt is maybe a bit high but not that bad.
 

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Sollace

Gold Supporter
Aug 16, 2020
533
Bryan TX
I appreciate all the comments. You need to realize I never took chemistry and math is not my subject. So all this was a huge learning curve.

Here we go:

3/10
PH 7.8
Chlorine was 5
Salt was 4400
CYA was 40
Calcium Hardness is 300 (3/8)
SWG is off

3/12
Added 4 cups m acid
1/2 cup stabilizer

3/14
1 cup m acid
1/2 cup stabilizer

3/15 (Morning)
Chlorine .5
PH 7.4
Salt 3400
Turned on SWG to 45%

3/15 (night)
Chlorine is back up to 5
PH is 7.6
Haven't updated CYA test yet. I know it needs to climb.

3/16
No testing yet
SWG turned down to 25% (Not sure of the setting yet for the right chlorine levels).
---------------------------------------
Observations: We're adding acid about every other day. Our water tests high for alkalinity, so there's that. Also our sense and dispense is tankless - Still missing that part and not idea when it'll come in. Which is fine. Whenever it comes in, it's going to sit until I get a good handle on all this! I'm also comparing my levels to what the pool warranty states:

C.L. Industries has endorsed the Langelier Saturation Index for over 25 years with great success. The care and feeding of your swimming pool is imperative. It is necessary for the longevity of the Exposed Aggregate Finishes, and as a condition of this warranty, that the following chemical parameters are maintained:

CL 1.0 – 3.0 ppm
pH 7.2 – 7.6
Total Alkalinity (TA) 80 – 100 ppm
Calcium Hardness (CH) 200 – 400 ppm (In warmer climates when water temperatures exceed 90 F calcium should be kept below 350 PPM)
Cyanuric Acid less than 50 ppm
Sequestering 10-12 ppm

*Failure to maintain the LSI within reasonable parameters voids the warranty.
*Extreme chlorine residuals maintained over the printed recommended residuals voids the warranty.

In areas where calcium levels exceed normal parameters, alkalinity and pH adjustments are required. The initial fill water is the most important water that the pool will receive. The initial fill water must be tested, recorded and adjusted to the above parameters before it has an opportunity to affect the new Exposed Aggregate Pool Finish.
 
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mguzzy

Gold Supporter
excellent.. you got the Salinity down to a reasonable level. Do realize the K1766 test will not read the same as your SWG display.. they calculate salinity differently. But here's the rub. the SWG will manage the operation of the cell based on what it reads, not what you test. So you kind have to dance between the two.. In the bigger picture if the SWG is happy let it ride. If you start to notice wild swings in Salinity that don't match your testing, then its likely the cell or controller is going on the fritz.

Your numbers look like a good start. I would refer you to the FC/CYA Chart and have you bring your CYA up to the SWG chart levels. It will allow the pool to retain more chlorine when you turn the SWG on. And yes you will see it use more acid.. that is a side effect of the electrolysis process. I keep my pH around 7.8. For the most part the alkalinity will find its own level, unless its way off I don't chase it too much.

As to the % output on your SWG controller.. everyone does it different... and everyone's pool is different. Here is my take on that. I try to find a runtime that will produce enough FC for my pool in average conditions with the SWG set at about 50%. That way I can turn it up or down to match the conditions. Lots of swimmers, weather gets hot, turn it up. Winter time cooler weather, turn it down. They idea is to find that middle ground where all you have to do is tweak the knob accordingly. If you are running full blast at 100% you have no wiggle room to turn it up. It probably took two seasons of living with it to figure that out for me.. and that was in my pre-TFP days. You can get a better idea by using the effects of adding in the PoolMath app and playing with the SWG settings for different runtimes.

Did you buy your Hubby that beer yet?
 
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JamesW

TFP Expert
Mar 2, 2011
24,208
Chloride and chlorine are basically the same atom except chlorine is missing two electrons.

The electrons get removed by the cell, which converts chloride into chlorine.

When chlorine works, it removes two electrons from something and it becomes chloride again.

When chlorine removes electrons from something, that's called oxidation.

So, the process is simply chlorine atoms gaining and losing electrons.

The total number of chlorine atoms stays the same.
 

mgtfp

Bronze Supporter
Mar 5, 2020
973
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
3/10
Salt was 4400

3/15 (Morning)
Salt 3400

Have you drained and refilled some water in-between those dates? Salt reduction by 1000ppm without major dilution is pretty much impossible. Or is this simply a typo?
 

mgtfp

Bronze Supporter
Mar 5, 2020
973
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
Chloride and chlorine are basically the same atom except chlorine is missing two electrons.

The electrons get removed by the cell, which converts chloride into chlorine.

When chlorine works, it removes two electrons from something and it becomes chloride again.

When chlorine removes electrons from something, that's called oxidation.

So, the process is simply chlorine atoms gaining and losing electrons.

The total number of chlorine atoms stays the same.

You nailed it, great explanation!
 

Sollace

Gold Supporter
Aug 16, 2020
533
Bryan TX
Have you drained and refilled some water in-between those dates? Salt reduction by 1000ppm without major dilution is pretty much impossible. Or is this simply a typo?

Yes, we dumped a bit over a foot of water from the pool. This is a new pool, completed and filled on February 3rd. When the pool guy finally came out to start up the SWG on March 9th, he dumped the salt in. Left the SWG on. It was on for a few hours before I was aware and then shut it off. Measured the salt and the chlorine and then did our own water dump.
 
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Sollace

Gold Supporter
Aug 16, 2020
533
Bryan TX
Did you buy your Hubby that beer yet?

!!!!!
Nope. Will a water do?
He's been so busy working on the yard. Today he's working on drainage from the back to the front yard, digging a ditch out to the sidewalk. I think he feels bad about draining our pool when water flowed into our neighbors back yard. She called both the pool and sprinkler guy worrying that something broke. . . Nope! Just us over here messing with our water.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
16,097
Evans, Georgia
You list test results for FC- please don't go 5 days between FC/CC tests. You ended up suddenly at 0.5ppm and that is just a disaster in the making as far as algae goes.

New pool owners should test FC daily then as they learn their pools you can extend that to OOD....

Maddie :flower:
 
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