Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 16 of 16

Thread: Correct Chlorine levels in Salt pool?

  1. Back To Top    #1

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Correct Chlorine levels in Salt pool?

    I have a stabilized salt water pool. What free chlorine level should I be aiming for? The test kits often say to aim for 1-2ppm, but I find the pool doesnt look as clear unless it's at 3+ ppm. If I let it drop to 1ppm it loses clarity. Maybe there's something else wrong?

    I haven't been monitoring combined chlorine so that could be an issue. I'm buying a FAS PDP test kit to start monitoring this.
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  2. Back To Top    #2
    BasicTek's Avatar
    Join Date
    Oct 2016
    Location
    Lake Mary, FL
    Posts
    795

    Re: Correct Chlorine levels in Salt pool?

    Your target FC should be based on your CYA level using this chart (the lower one for SWG's) Almost all SWG's should be 60-80 CYA so your target will likely be 4-6
    -Tim-
    Pool: 86 gunite/plaster screened IG 12K 14' X 29', Hayward 120 sq ft cartridge filter, Pentair Intelliflo 2 VST, Hayward SwimPure 40K SWCG, Hayward Poolvergnuegen autovac,
    Heat: 280 sq ft Ultrasun solar Panels, Pentair Solartouch Ctrl, (solar cover and reel)
    Tests: Taylor K-2006C & K-1766 w/ speedstir

  3. Back To Top    #3

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    Quote Originally Posted by BasicTek View Post
    Your target FC should be based on your CYA level using this chart (the lower one for SWG's) Almost all SWG's should be 60-80 CYA so your target will likely be 4-6
    Thank you!

    How come test kits say 1 to 3 or thereabouts?

    Why the difference compared to the chart? It seems to be very large differences.
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  4. Back To Top    #4
    BasicTek's Avatar
    Join Date
    Oct 2016
    Location
    Lake Mary, FL
    Posts
    795

    Re: Correct Chlorine levels in Salt pool?

    Quote Originally Posted by tomfrh View Post
    How come test kits say 1 to 1.5 (or 1 to 3) is ideal if in many cases it needs to be higher than that?
    The industry is terrible about maintaining chlorine based on CYA, but if you want a properly clean pool I've never had an issue following that chart, I've never shocked my pool or had algae since either.
    -Tim-
    Pool: 86 gunite/plaster screened IG 12K 14' X 29', Hayward 120 sq ft cartridge filter, Pentair Intelliflo 2 VST, Hayward SwimPure 40K SWCG, Hayward Poolvergnuegen autovac,
    Heat: 280 sq ft Ultrasun solar Panels, Pentair Solartouch Ctrl, (solar cover and reel)
    Tests: Taylor K-2006C & K-1766 w/ speedstir

  5. Back To Top    #5

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    Thanks. I'll use the chart from now on. I've never factored in CYA. I didn't know it made a difference.
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  6. Back To Top    #6
    JoyfulNoise's Avatar
    Join Date
    May 2015
    Location
    Tucson, AZ
    Posts
    14,225

    Re: Correct Chlorine levels in Salt pool?

    Quote Originally Posted by tomfrh View Post
    Thanks. I'll use the chart from now on. I've never factored in CYA. I didn't know it made a difference.
    I suggest you read the Pool School articles on this site and do a little studying. This thread is a bit older but it shows how TFP is lightyears ahead of the pool industry -

    Certified Pool Operator (CPO) training -- What is not taught
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  7. Back To Top    #7

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    Quote Originally Posted by JoyfulNoise View Post
    I suggest you read the Pool School articles on this site and do a little studying. This thread is a bit older but it shows how TFP is lightyears ahead of the pool industry -

    Certified Pool Operator (CPO) training -- What is not taught
    Thanks. I'll do that. I thought I had some understanding of chemistry, but clearly I'm wallowing in ignorance.

    This site reminds me of when Homer joins the secret society and they give him the real emergency phone number - 912
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  8. Back To Top    #8
    BasicTek's Avatar
    Join Date
    Oct 2016
    Location
    Lake Mary, FL
    Posts
    795

    Re: Correct Chlorine levels in Salt pool?

    You know what's crazy, go to any major site that sells anything like pool supplies, leslies, lowes, even angies list and look up what the recommend for pool maintenance. You will see everywhere they recommend FC levels that are too low and to compensate they recommend to shock your pool weekly. It's unbelievable that people are doing this all the time.... Another thing that's crazy is almost everyone I know uses a chlorine feeder that adds consistent CYA to their pools. So in no time at all the CYA is too high for the recommended FC, and after any lengthy period of time even FC of 20 isn't enough, and only draining the pool will really straighten things out. This is considered normal pool maintenance.
    -Tim-
    Pool: 86 gunite/plaster screened IG 12K 14' X 29', Hayward 120 sq ft cartridge filter, Pentair Intelliflo 2 VST, Hayward SwimPure 40K SWCG, Hayward Poolvergnuegen autovac,
    Heat: 280 sq ft Ultrasun solar Panels, Pentair Solartouch Ctrl, (solar cover and reel)
    Tests: Taylor K-2006C & K-1766 w/ speedstir

  9. Back To Top    #9
    needsajet's Avatar
    Join Date
    Jan 2016
    Location
    Sydney, NSW, Australia
    Posts
    4,540

    Re: Correct Chlorine levels in Salt pool?

    Unfortunately, the recommendations that come with pool equipment are not adequate for keeping a pool open and consistently clean. FC at a minimum of 7.5% of CYA is only very, very gradually getting recognized, despite it being 45 year-old science. Equipment manufacturers just parrot the typical pool industry numbers.

    When a pool is stabilised, roughly 95% of the chlorine is tied up with CYA, and not active. The other 5% is the active chlorine, including hypochlorous acid (HOCl) which is the active sanitiser and sometimes called the "harsh" part of the chlorine. Drinking water here in Sydney is around 0.7 ppm FC (never any CYA of course), and the HOCl is 0.22 ppm. In a pool with FC at 7 ppm and CYA at 70 ppm, there is 0.04 ppm HOCl (about 1/5 as "harsh" as the drinking water). (both compared at pH 7.8)

    You need roughly 0.02 ppm HOCl to prevent algae from gaining a foothold, and around 0.01 ppm HOCl to control target pathogens. Most of the pool industry merely says to keep CYA under 100 ppm and FC at 1-3 ppm. Those conditions are dead wrong and ineffective, because the HOCl level is 0.003 ppm at 1 ppm FC and 100 ppm CYA, which is why people end up having to "shock" weekly. The pool chemical and general pool industry appears to be reluctant to share the correct information, probably because it would hurt overall chemical and other sales.

    Luckily for us here in Aus, we're in front. A good source is a chlorinating liquid label (see below). Pool chems here are regulated by the Australian Pesticide and Veterinary Medicine Authority (APVMA), and label information needs to be supported by science. CYA is recommended to be kept from 30-50 ppm, and the label refers only to minimum chlorine levels (2-3 depending on temperature), plus there are higher recommended levels for clearing algae. There's a few things that could be better on the label, but at least with respect to FC-CYA, the numbers are reasonably compatible with TFPC recommendations.
    Aus Chlorine Label.jpg
    12k IG salt; glass beads in plaster; K-2006C, K-1766, K-1106 and CCL test kits; Pentair Eco800 1.2HP VS; Zodiac SWCG 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; Other family pools 10K SWCG and 15K on liquid; PoolMath app subscriber; | Tips for New Members to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

  10. Back To Top    #10

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    Drinking water here in Sydney is around 0.7 ppm FC (never any CYA of course), and the HOCl is 0.22 ppm. In a pool with FC at 7 ppm and CYA at 70 ppm, there is 0.04 ppm HOCl (about 1/5 as "harsh" as the drinking water)
    Wow. So high FC isn't necessarily harsh? I was working under the assumption that anything over about 5ppm was really harsh.

    I had no idea the conventional wisdom was so crude.

    I really need to read the pool school articles.
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  11. Back To Top    #11
    needsajet's Avatar
    Join Date
    Jan 2016
    Location
    Sydney, NSW, Australia
    Posts
    4,540

    Re: Correct Chlorine levels in Salt pool?

    CYA is great stuff at the right level

    The concentrations of the various forms of chlorine reach an equilibrium quickly, so that when HOCl is used up doing the sanitation work, more is released from the CYA, so it's always there for sanitising. When free chlorine gets too low, we replenish it, and CYA grabs most of it, ready for the next time it's needed. So the FC attached to CYA acts like a reserve and buffer.

    When people experience what they think is the harshness of chlorine, it's usually when active chlorine has been too low, and too much chloramine is created (motel pool smell), or indoor pools with no CYA when the active chlorine is high enough to (e.g.) wear out the elastic in swimmers, or to form a lot of chloramine on their skin by combining with sweat. The smell that people typically call "chlorine smell" is chloramine, not chlorine which has no smell to it. A pool shop guy demonstrated it me this way... open a brand new jug of chlorine or bleach and sniff it, and there's zero odor. Now stick a finger in it, smell your finger and you'll detect "bad pool smell" because sweat (which contains ammonia) combines with chlorine to form chloramine.

    Pool school is very helpful, and if you want a deep dive on chlorine and CYA, this thread has all the FC/CYA detail covered in the first few posts. I think I read it ten times before it made sense for me! Pool Water Chemistry
    12k IG salt; glass beads in plaster; K-2006C, K-1766, K-1106 and CCL test kits; Pentair Eco800 1.2HP VS; Zodiac SWCG 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; Other family pools 10K SWCG and 15K on liquid; PoolMath app subscriber; | Tips for New Members to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

  12. Back To Top    #12

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    Oh, so CYA is essentially a reservoir/buffer for the chlorine, that accepts/releases Chlorine according to equilibrium? Is that right?
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  13. Back To Top    #13
    needsajet's Avatar
    Join Date
    Jan 2016
    Location
    Sydney, NSW, Australia
    Posts
    4,540

    Re: Correct Chlorine levels in Salt pool?

    Fair dinkum. Struth mate. And well said!
    12k IG salt; glass beads in plaster; K-2006C, K-1766, K-1106 and CCL test kits; Pentair Eco800 1.2HP VS; Zodiac SWCG 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; Other family pools 10K SWCG and 15K on liquid; PoolMath app subscriber; | Tips for New Members to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

  14. Back To Top    #14

    Join Date
    Jan 2018
    Location
    Australia
    Posts
    337

    Re: Correct Chlorine levels in Salt pool?

    What about this supposed “sunscreen” effect of CYA? What about that?
    50,000L, IG (in ground), Concrete/marblesheen, 40 years old, Sand filter (Zelbrite media), Davey PM Eco (1600rpm), SWG, Clear Choice Labs Testing Kit, solar (25m2 tubes, Davey wisper 500 Boost pump), Zodiac vx50 robot cleaner

  15. Back To Top    #15
    needsajet's Avatar
    Join Date
    Jan 2016
    Location
    Sydney, NSW, Australia
    Posts
    4,540

    Re: Correct Chlorine levels in Salt pool?

    That's also pretty well known. Without allowing anything for FC losses from oxidising organics, FC on it's own in sunlight in your pool water has a half-life of around 40 minutes, vs. around 8 hours with CYA in the water from about 30 ppm CYA on up.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, K-1106 and CCL test kits; Pentair Eco800 1.2HP VS; Zodiac SWCG 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; Other family pools 10K SWCG and 15K on liquid; PoolMath app subscriber; | Tips for New Members to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

  16. Back To Top    #16

    TFP Guide
    lightmaster's Avatar
    Join Date
    Jun 2017
    Location
    Baxley, GA
    Posts
    799

    Re: Correct Chlorine levels in Salt pool?

    Quote Originally Posted by BasicTek View Post
    You know what's crazy, go to any major site that sells anything like pool supplies, leslies, lowes, even angies list and look up what the recommend for pool maintenance. You will see everywhere they recommend FC levels that are too low and to compensate they recommend to shock your pool weekly. It's unbelievable that people are doing this all the time.... Another thing that's crazy is almost everyone I know uses a chlorine feeder that adds consistent CYA to their pools. So in no time at all the CYA is too high for the recommended FC, and after any lengthy period of time even FC of 20 isn't enough, and only draining the pool will really straighten things out. This is considered normal pool maintenance.
    Best way to make money selling solutions to a problem, is to ensure there's a problem in the first place. Set the building on fire so you can come to the rescue to put it out. Just look at the cigarette industry, putting chemicals into the cigarettes specifically to make them more addicting, so people buy more and more of them.

    - - - Updated - - -

    Quote Originally Posted by tomfrh View Post
    Wow. So high FC isn't necessarily harsh? I was working under the assumption that anything over about 5ppm was really harsh.
    I've swam in my pool when the FC was at 12ppm (raised it to shock levels when I went out of town for the weekend and it was still falling back down to my target of 7ppm) and I didn't notice anything unusual about the water, no harsh taste or smell.
    Pool Stats: 18' X 48" Vinyl AG, 6,700 gal, Hayward Power-Flo LX 1hp and Easy-Clear C400 cart, Circupool RJ-45 SWG, Dolphin S300, My AG Pool Mods
    Helpful Links: Pool Logger, PoolMath, TF100 test kit, Recommended Chemical Levels, Ext Test Kit Directions, FC/CYA Chart, Chlorine Date Code Calendar, Polyfill Iron Removal, Borates Drop Test

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •