Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 7 of 7

Thread: Effect of Cyanuric Acid on ORP (with automated systems)

  1. Back To Top    #1

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Effect of Cyanuric Acid on ORP (with automated systems)

    I am not offering an opinion either way; that can be dangerous. Simply asking for opinions on this article:

    http://www.poolspanews.com/2008/052/052acid.html

    Looking forward to replies.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    That is a fairly decent article.

    The 2004 Arch Chemical study on plaster problems from high CYA has not been duplicated and some doubt that that effect actually occurs. The observed effects may simply be from low PH, which often occurs at the same time as high CYA levels.

    The highest practical CYA level for use with ORP is often much higher than 20, though it varies. ORP is often usable with CYA up to perhaps 50 or a little more, though the FC level does vary more over the course of a day than it would with CYA at 20.

    The "Stabilization with Cyanuric Acid" chart is not accurate. The effect is similar to what they show, but higher CYA levels provide more protection from sunlight than that chart indicates.

    They also fail to explore the CYA/FC relationship, emphasizing how FC at a constant level becomes ineffective at higher CYA levels. It is simple enough to raise the FC level to compensate.

    Despite these minor flaws, that is a fairly good article. The industry has been in denial about the problems of high CYA levels for so long, it is good to see someone starting to get it right.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    JasonLion,

    Thank you for your clear and polite response, I did learn from what you wrote.

    One query I would like you to help me with is where you write,"The "Stabilization with Cyanuric Acid" chart is not accurate. The effect is similar to what they show, but higher CYA levels provide more protection from sunlight than that chart indicates", can you direct me to a link for this type of chart? I would be interested to view it.

    I fully agree with you when you state "It is simple enough to raise the FC level to compensate." Albeit so long as ones SWG is large enough.

    We have the PoolPilot Total Digital SC-60. The ORP is set to cut off at 700, the power setting is 2. In our 10,000 gal pool with salt at 3500 and CYA at about 30 (allowable per their manual), and running for 4 1/4 hours (a 1.3 turn), from 11 am to 3:15 pm, it maintains a FC of 5, which seems to hold throughout the day. ph is 7.4, alkalinity 70, borates, 50, calcium 600, av.temp 84.

    The ORP reading normally starts off at 660 or 665, then moves to about 685 by noon, dropping back to 660 by 1:30 pm, and closing at about 685 -690 depending if it is cloudy or not. If I turn it on at night for an hour, when I swim, it might be 705 or so. We use to have the pH at 7.5, but 7.4 gives a slightly better and more consistent ORP value.

    If I run the unit longer say 12 hours, when the grandkids are in and out it most of the day, the ORP will rise to around 728 in the evening. The next morning it will start off at a higher reading say 685, but the FC will still be pretty rock constant throughout at 5.

    I think more turns on the water have an effect on the ORP values, with possibly clearer water come less contaminants, yes no I am not sure, what do you think? The article is interesting, if I am reading it correctly, that lower CyA at 20 may produce more stable and potentially higher ORP readings. When and if I have the time I will try this out at 25 CyA, then, 20 CyA, reducing my FC to 4 then 3.5, and see if this is true. Also I will see if this creates any other problems and then report back, though that may be some time in the future, as I will let the CyA drop over time.

    I do realize that ORP is not the be all and end all of sanitation, HOCl (as ppm Cl2) is more important. But if one can run at a lower FC then the cell unit might not be on all the time it is running and save on electricity. It is at least worth a try. I fully understand the argument for high CyA 60 - 80 for saltwater pools but here in Hawaii it does not seem to work as well.

    I do not know why but algae starts to rear its ugly head, it most probably has something to do with high UV radiation in a short day year round at a 21.3 degrees latitude from the equator. A lower CyA of 30 with the above numbers works better for us (and my neighbours) with a FC of 5, drop it to 4 or below and trouble starts. I fully realize that other CyA numbers and FC numbers work perfectly well on the mainland and maybe in other parts of Hawaii.

    So I will test their ideas; maybe they will bomb, possibly life may getter cheaper, who knows.

    To those certain person(s) that may wish to repeat to me that my pool is not a science experiment I would like to kindly remind you it is our pool, so I think we are entitled to our little experiment. And what harm can come of it, maybe we will all learn something. As the old saying goes "A wise man does not know, and a fool will not listen". So I will try to learn something, by listening to this article.

    Aloha
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  4. Back To Top    #4

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    28,417

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    This should be in "The Deep End".

    Moved. JasonLion
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    There was a discussion about the shielding effects of higher CYA levels in this topic. We don't have enough data to update the chart, but there is enough information to show that the chart is not accurate at higher CYA levels.

    Keeping FC around 5 with a SWG and CYA at 30 is much higher the is necessary. I would keep FC around 2 or perhaps 3. If you are experiencing problems when FC goes below 5, you probably need to shock the pool to eliminate any lurking algae.

    ORP readings will fluctuate between daytime and nighttime by between 20 and 40, lower during the day.

    Lower CYA levels will produce higher ORP readings, but that isn't a good, or bad, thing. Effectiveness against viruses/bacteria/algae is more directly correlated with the HOCl level than it is with the ORP level. Adjusting CYA and FC together to maintain constant HOCl levels, as in the FC vs CYA chart, will have uniform effectiveness against contaminates but will give lower ORP readings at higher CYA levels.

    Higher CYA levels will reduce the required cell run time. It sounds like you have the cell constantly on for four hours, which is a very long run time for that size cell and small pool. However, you don't want CYA above about 50, or you will start to see fluctuations in the FC level during the day.

    There are also secondary effects to keep in mind. The acid feed system on the Total Control unit can't always keep up with the SC-60 cell on full. If you have that issue the PH will fluctuate somewhat during the day, which will cause the ORP reading to fluctuate, which can cause the FC level to fluctuate.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  6. Back To Top    #6

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    JasonLion,

    Thank you for your response. What you stated makes a lot of sense and the suggestions are obviously based on real life experience rather than chemistry or physics. So here comes my real life experience rather than theoretical practise.

    Well I think I am finally onto something, I lowered the CyA to 25, raised the pH to 7.5 although it seems to hold at 7.45, and lowered the ORP to 690.

    The results are amazing, the ORP stays at around 695, slightly higher in the morning at around 703, slightly lower around noon to 1 pm, then back above 690, the pH as stated is pretty much static at 7.45. The FC at around 4.0 to FC 4.5. The pump now runs for 4 1/2 hours about a 1 1/2 turn, use to go 3 1/2 hours, I think that helps as well. This gives HOCl (as ppm Cl2) around 0.074, and of course the SWG runs infrequently.

    I will let this experiment go for a week and see how it does. The reason maybe is that our daylight hours in the summer and winter fluctuate less than yours on the mainland but our UV intensity is much greater so you may lose more FC as your light hours during the summer swimming season are considerably longer than ours. I really do not know why this is happening, but who cares it works, or maybe the posted article really does have it right. Maybe someone wants to try it in say PA, NJ, or NY. But because of your longer days and lower UV in season, versus our relatively short days with mild fluctuations of UV, I think your higher CYA principal will work better. It seems to be a case of different strokes for different folks, although the very far south of Florida may benefit from this posted article.

    For Info:

    Honolulu, Hawaii

    Date Sunrise Solar Noon Sunset Daylight Hours

    Jun. 23 5:50 a.m. 12:32 p.m. 7:16 p.m. 13 hrs. 26 min.
    Dec. 21 7:04 a.m. 12:30 p.m. 5:55 p.m. 10 hrs. 51 min.

    Aloha.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  7. Back To Top    #7

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Re: Effect of Cyanuric Acid on ORP (with automated systems)

    JasonLion,

    A quick update. I had to drain my pool this morning by 24%, as the salt was too high at 4200. Lowered it to 3200, added CyA only to get it back up to 20 not 25 as in the previous post. At 4 pm today the ORP was 719, and set at 700, pH was 7.5. I will update the observation next week Sunday, I hope. But this low CYA level approach seems to work, at least in Hawaii.

    The numbers look like this:

    Measured pH 7.5
    Total Alkalinity (ppm CaCO3) 70
    Free Chlorine (ppm Cl2) 3.0
    Cyanuric Acid (ppm CYA) 20
    Calcium Hardness (ppm CaCO3) 425
    Total Dissolved Solids (ppm) 3,548
    Total Sulfate (ppm SO42-) 0
    Total Borate (ppm Boron) 40.0
    Total Ammonia (ppm Nitrogen) 0.0
    U.S. Gallons 10,000
    Temperature (oF) 84

    Total Chloride (ppm NaCl) 3200
    Carbonate Alkalinity (ppm CaCO3) 58.2
    Langelier Saturation Index (LSI) -0.08
    % HOCl (vs. Total Free Chlorine) 2.2%
    OCl- (as ppm Cl2) 0.082
    HOCl (as ppm Cl2) 0.066
    Calcite Saturation Level (CSL) 0.62
    Calcite Saturation Index (CSI) -0.21



    Aloha.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

Posting Permissions

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