Long Term consequences of liquid chlorine as a by product of Salt? Are there any?

[Catanzaro]

I enjoy reading the forum even though my pool has been closed here in NJ. This morning the temperatures were at 43 degrees so the bad news is that there will be no swimming until next year. Good news is that I have all winter to educate myself on the TFP method. I feel pretty good about the method already.

Lately I have come across information on salt as a byproduct of liquid chlorine and there was a post back in 2013 from Chem Geek that stated that for every 10 ppm of FC in chlorination liquid there is around 8-9 ppm of salt added to the pool & when the chlorine gets used/consumed, there is another 8-9 ppm of salt added to the pool for a total of 17 ppm salt. This is easy to understand as it is basic math.

Further reading suggests that people have very high levels of salt in their pools. But how much is too high? . I fully understand that higher salt is better then higher CYA. A few questions:

Q: I have the TF-100 Test kit but do not remember reading about testing for salt. Can I order something to test for salt and if so how often should I be testing?

Q: At what levels does salt pose a potential problem for a vinyl liner swimming pool and what are the adverse effects if any?

Q: Does salt naturally disappear when the pool is closed for 8 months during the course of the year?

Q: Are there chemicals to reduce the salt content in swimming pools or is a drain-fill the only option just as if your CYA was too high?

I switched to the BBB method halfway during the year and removed the Frog Mineralizer and Bac Pacs. My CYA level stayed consistent at around 40. For about 2 months before the pool was closed I added around 2 ppm daily of liquid chlorine so my salt readings should not be too high. I kind of miss testing my pool water with the TF-100 (maybe because I really never liked chemistry or science in School) LOL

 

[Smykowski]

My thoughts are in red....

Q: I have the TF-100 Test kit but do not remember reading about testing for salt. Can I order something to test for salt and if so how often should I be testing? There isn't a test in the TF100. Yes, there is another test you can order, but unless you have an SWG where a precise salt level is important, no one really bothers.

Q: At what levels does salt pose a potential problem for a vinyl liner swimming pool and what are the adverse effects if any? No. SWGs require about 3000ppm of salt. Most manually chlorinated pools (this is anecdotal...) seem to stabilize in the teens.

Q: Does salt naturally disappear when the pool is closed for 8 months during the course of the year? Nope, it's like CYA. Splashout or drain and fill only.

Q: Are there chemicals to reduce the salt content in swimming pools or is a drain-fill the only option just as if your CYA was too high? Nope, see above.

If you drain water when closing, you will be very hard pressed to have your salt level climb very high. If it does climb, it will take years.

.... I kind of miss testing my pool water with the TF-100 (maybe because I really never liked chemistry or science in School) LOL That's awesome!

 

[duraleigh]

Residual salt from liquid chlorine is virtually never a problem. Any build-up is normally diluted and exchanged out with refill/rain water.

Of all the reported issues here on the forum, excess salt (unless you put too much in yourself) is seldom, if ever, reported.


1. You can order a salt test strips from several manufacturers (TFTestkits carries Aqua-chek brand) or you can get a Taylor drops based kit (K-1766) that is more accurate. I would personally not spend the money.

Your salt content will be far less than those pools that produce chlorine with an SWG.

 

[BoDarville]

Q: At what levels does salt pose a potential problem for a vinyl liner swimming pool and what are the adverse effects if any?

No. SWGs require about 3000ppm of salt. Most manually chlorinated pools (this is anecdotal...) seem to stabilize in the teens.

This has been my experience. I've been using the TFP method for about 3 1/2 years and the maximum salt level in my pool has been 1,560 ppm - about half the typical level of a SWG pool. Plus I keep my pool open year-round, meaning I do not do a partial drain / refill like those who close / open their pools on a seasonal basis. Salt level in my pool over the past year has been in the 1,040 to 1,560 ppm range - highest in early fall and lowest in mid-spring.

 

[chem geek]

It really all comes down to water dilution. With an oversized cartridge filter, then there would be minimal water dilution from cleaning it say once a year. However, you have a sand filter so the regular backwashing contributes to water dilution. If you lived in an area with no summer or winter rain overflow (it could rain, but only enough to make up for evaporation and not enough to overflow the pool water) then there would be no water dilution.

In my own pool, I have an oversized cartridge filter so I use winter rain overflow as my primary way to dilute the water each season where water from my pool cover pump gets put into the pool and overflows into the sewer drain. I only have 1 ppm FC per day chlorine usage due to my mostly opaque pool cover and my salt level usually stays in the 1000-1500 ppm range as a result.

If you were to backwash your sand filter weekly, say with 300 gallons (60 GPM for 5 minutes), then that would be 300/14700 = 2.0% dilution per week. A chlorine usage of 2 ppm FC per day would increase salt by 23 ppm per week so the steady-state salt level would be 23/0.02 = 1150 ppm.

In Howell, New Jersey where you live, the monthly weather data shows rain every month from roughly 3" to 5" per month. As shown in this link there is significant evaporation from May to August exceeding rain amounts unless you used a pool cover. So you may not get rain overflow during the spring and summer, but may during the winter. Of course, if you close your pool then you may partially drain it and then refill it on opening which would dilute the water.

 

[Catanzaro]

You are 100% correct, not that much rain during the swimming season in NJ. There is just enough rain to compensate for the evaporation. I believe that the pool was filled up about 2" twice during the season. As for the backwashing, my pressure only increased by 25% twice during the season. I only had to backwash 2X in a 3 month period after the concrete was poured.

I do not have a cover and based on my 2 ppm increase daily under cool conditions this summer my salt level would increase over time. Not that much activity because of the weather. I am assuming I would loose about 3 ppm daily if the weather reaches normal temperatures here in NJ. The pool was not drained upon closing either. Unfortunately my contract states that the Pool Company must close the pool to honor the warranty (no big deal as it was not that much).

In my situation, will I ever get to a level high enough where I will have to drain and refill? Just curious. Thank you.

 

[duraleigh]

will I ever get to a level high enough where I will have to drain and refill?

No, not for salt.......it just doesn't work like that.

 

[Catanzaro]

Thanks to everyone for clearing up this confusion.

 

[chem geek]

Well, if there was hardly any water dilution at all, then over years the salt level could get pretty high, even higher than 3000 ppm used in saltwater chlorine generator pools, so if it got to that level in a pool or spa not designed with high quality stainless steel, then that could be a problem, or if it got to 5000 ppm or higher then I'd start to worry about possible metal corrosion. It's not absolute -- just increased risks.

At 2 ppm FC per day so 100 ppm salt increase per month, that's 600 ppm per year for a roughly 6 month season so it will certainly take some time to get very high. With an all-year open pool, then it still would take years at 1200 ppm/year increase (4 years would be nearly 5000 ppm). Nevertheless, I wouldn't tell someone it's never a problem since if they truly had minimal water dilution then they could come back 5 years from now and complain about the increased metal corrosion in their pool -- certainly they'd be tasting the salt level by then.