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Thread: chlorine goes away *very* fast

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    chlorine goes away *very* fast

    I'm trying to switch to BBB. My levels were all wrong, and I'm pretty sure I adjusted them in the wrong order so everything got a bit high. I don't think that should have affected what I'm seeing, but maybe so....

    the problem:
    this afternoon I added 1 gallon of 10.5% bleach (from pool store, was told it was fresh this morning). I tested with OTO kit after 30 minutes (giving it time to circulate). I had a dark yellow color. After 30 more minutes, barely a trace, and DPD said 1ppm FC, 1.5ppm CC.

    This past weekend, over a 15 hour period I added 2.5 gallons 10.5% bleach, 2 pounds 73% calcium Hypochlorite, 1 lb dichlor. A couple hours later, OTO said barely detectable chlorine. How could it go away that fast? Pool is sparkling, BTW.

    current levels:

    cya 60 (I thought hot Florida sun was baking out my chlorine, so added cya to bring it up from 30. Probably not best move.)
    ch 510 (I believed pool store when they said my CH was low, and added 15 lbs CH. Definitely a bad move -- and why I bought TF100).
    ta 120 (I brought it UP to 80 with baking soda before adding boric acid. Probably not best move).
    borate 80 (I brought it up to 60 before adding borax to adjust PH from adding cya. Probably not best move).
    ph 7.5 (brought up from 7.0 with borax and washing soda before adding cya, then more borax after cya).
    FC/CC 1/1.5

    all tested with a TF100 that is about a week old.

    My regime over the past year was to toss in a pound of dichlor w/copper (aquachem blue) every week, which actually did a pretty good job. I'm in Florida with solar heat, so pool is open year round (though 3 or four months of that it is a bit on the chilly side!). I ordered a Stenner to feed bleach, but if I can't get chlorine to stay in the pool I don't think I can feed it fast enough (not to mention the expense).

    any thoughts? Maybe if I keep pounding the chorine (ie slam) it will eventually stop?

    thanks,

    geoff
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Re: chlorine goes away *very* fast

    One pound of Dichlor in 12,500 gallons increases the CYA by 4.8 ppm (and the FC by 5.3 ppm). So if done once a week for 6 months that would increase CYA by 123 ppm. Unless your pool water chemistry numbers are from your own TFTestkits TF-100 or Taylor K-2006 test kit, then I would not trust them. Your CYA level is probably higher than you think. Also, 5 ppm FC per week is not enough chlorine if your pool is uncovered and exposed to sun (is your pool under a partial screen as is sometimes the case in Florida?). More typical chlorine usage in full sunlight is 2-3 ppm FC, depending on CYA level. If you have a partial screen, then it's possible to be at 1-2 ppm FC per day.

    I suspect your CYA level is too high and that as a result algae is able to grow faster than chlorine can kill it. You are in the "nascent algae growth" stage which is before it becomes visible. Since you presumably have copper in the pool this is a bit surprising, but who knows what the copper level actually is since it's hard to regulate and we don't recommend it due to the risk of staining plaster surfaces and turning blond hair greenish.

    You need to SLAM your pool, but before doing so I would get a proper test kit and find out your true CYA level. If it's very high (above 80 especially), you should do a partial dilution to lower it. And you'll need to stop adding any stabilized chlorine (Dichlor or Trichlor) products to your pool which only make the problem worse because they increase the CYA level.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: chlorine goes away *very* fast

    I did say my testing was done with a week-old TF100. I had a CYA of about 30 before adding a pound and a half of stabilizer. I've also added several pounds of dichlor while trying to get any FC to last more than a couple of hours. I tested it today around 60. Perhaps it was as high as 80, but I saw a ghost of the dot still moving at 80 on the tube, and at about 60 it was completely gone.

    My TA was down around 30 when I started the whole balancing thing. I guess I misunderstood the posts about getting the TA to 80 before adding borates. I had added borax a few years ago (I still showed about 15 ppm on the test strips) and liked it, so I wanted to get back there. If I had realized adding the borates (and likely the washing soda and borax for pH) would add that much TA I wouldn't have raised it with baking soda. But I saw a lot of posts saying it was really hard to change the TA after borates, so do it before....

    So why should my CYA levels (and TA levels) have been so low? We had one **** of a rainy summer in Tampa. Epic.

    My pool has an automatic overflow (not quite sure where it overflows to, but there is a pvc tube in the strainer and the water level falls below that within a day of rain (or me forgetting to turn off the hose!) putting it over that level, so the pool was undoubtedly overflowing all summer.

    So if I do indeed have this nascent algae....

    According to the pool calculator I added about 40ppm of chlorine in a 15 hour period and it was almost undetectable two hours after the last addition. Today I added a gallon of 10% and it was almost undetectable an hour later.

    Would organics in the water take the chlorine down this rapidly? The idea of doing a slam as in keeping chlorine high even for a 24-hour period does not seem achievable at this point. Even a two-hour period would be a stretch.
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Mod Squad jblizzle's Avatar
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    Re: chlorine goes away *very* fast

    Just keep adding liquid chlorine. Something in the water is consuming it. Just dose for SLAM level, and then test the FC and CC after an hour and re-dose back to SLAM level, rinse and repeat. You should start to see the FC lasting longer and the CC diminishing.

    Assuming the CYA is at 60ppm as you tested and do NOT use any chlorine except the liquid/bleach. You CYA and CH are already on the high side and you do not want to be raising them any higher.
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    Re: chlorine goes away *very* fast

    Thanks, I'll give that a try. This may be a stupid question, but after I add the bleach, any idea how long it should take until it is well mixed in the pool? As my .sig says, I've got a skimmer, kreepy krawley, waterfall, and three jets all sucking or squirting away....
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Smykowski's Avatar
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    Re: chlorine goes away *very* fast

    30 minutes should be enough.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: chlorine goes away *very* fast

    perhaps I see the problem.... The water looks fine during the day, but tonight I have the pool light on while I'm adding bleach and taking measurements. The amount of solids floating in the water illuminated by the pool light is truly amazing. And not in a good way.....

    While no one could know how much bleach it is eventually going to take to do the slam on the pool, does anyone have a guesstimate on the amount of bleach taken for the worst pool in their experience? At least that might give me an idea of what I'm facing. 20, 30 gallons of 10%? More?

    thanks!

    geoff
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Re: chlorine goes away *very* fast

    Based on the amount of dichlor added, one would expect the CYA to be very high (as chem geek said). Your low CYA might be due to bacteria converting the CYA into ammonia. This could account for your high chlorine demand.

    Keep adding liquid chlorine to Slam level for as long as it takes.

    Are you getting any chloramine readings or smell?

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    Re: chlorine goes away *very* fast

    no smell. cc is 1 1/2 - 2ppm. NWS says we got more than three feet of rain this summer. That could dilute cya amounts a tad, could it not? My pool only runs from 3 1/2' to 5 1/2' in depth.
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Re: chlorine goes away *very* fast

    Without knowing more history, I think that CYA to ammonia conversion by bacteria best fits the available information.

    I recommend adding 4 gallons of 8.25 % bleach or 3 gallons of 10.5 % sodium hypochlorite and then retesting for FC and CC with FAS DPD in 30 minutes and then again in one hour.

    Continue following the Slam process as described in Pool School.

    Do you know of any contaminant that got into the water?

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    Re: chlorine goes away *very* fast

    Just a reminder of a basic concept.....Two things consume chlorine. Organics in your pool and sunlight.

    That you have some CYA (I would trust your test results, regardless of how they got to that level) greatly reduces the effect of the sun so you are left with organics in your water. SLAM is the correct procedure. Your FC consumption will drop dramatically as you continue the slam and the organics are killed.

    You have a few newbie peripheral issues but stay focused on the SLAM.
    Dave S.
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    Re: chlorine goes away *very* fast

    The correct answer is as the mods are saying. Bring FC to slam level (for your CYA), test frequently and keep it there...(until you pass your tests - but it doesn't hurt to keep it high a day or two longer, after passing all three tests just to be sure).

    But to answer your other question, it may take dozens of gallons of bleach, especially if it's a lower %. I know it's good to hear someone say that the use of massive quantities of bleach is not unreasonable. Just do the math and testing and the amount of bleach needed is what it is, no matter the tonnage required.

    I SLAMed once because I let my FC drop too near 0. It took 14 gallons of the 12% bleach over four days. My CYA was around 70 though due to using a SWCG. It was precautionary and sort of experimental in my case, but I knew it couldn't hurt anything.

    Trust the masters (which does not include me, though I do feel empowered to take care of my own pool).
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    Re: chlorine goes away *very* fast

    Well, it didn't take as much more as I had feared. I added 2.5 gallons 10% bleach, two hours later, chlorine gone. Did it again, two hours later, chlorine gone. The third 2.5 gallon addition did the trick. A day later I was still at dark yellow on OTO, so did an overnight FAS test. Perhaps I'm not quite there, but I'm close. Last night, 11.5ppm FC, no CC, this morning 10.5ppm FC, 1ppm CC.

    And that's 30 hours after the last addition of bleach -- and yesterday was a very bright sunny day. I'll get there yet!

    geoff
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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    Re: chlorine goes away *very* fast

    Excellent progress!
    18'x38' Rectangle (3'-8 1/2' deep w/ diving board) - 27K gal. w/ gray plaster
    Hayward equipment (cartridge filter, 2-speed pump, SWCG, automation) View Our Build
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    Patrick_B's Avatar
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    Re: chlorine goes away *very* fast

    Way to go Geoff! Welcome to TFP and a better way of caring for your pool.
    TFP Moderator
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  16. Back To Top    #16

    Re: chlorine goes away *very* fast

    Just a bit of a follow-up.... My FC was about 10 before I went away on the weekend (a couple of days after my last post). I received and installed a Stenner 10gpd pump, and had it set for 1/2 gal per day just before I left. According to the pool calculator, that should add 4ppm or so per day. It added 1 1/4 gal over the weekend before I got home. I had FC of 16. When I burned out the organics with SLAM, I guess I burned them out good! I turned off the Stenner, and it has now been a week since I added any chlorine. I measured it today at 10ppm. The pool has had almost no use, and I have a high CYA at around 60ppm so I guess that has been protecting the chlorine from the sunshine. We had a few cloudy days here in Tampa this past week, but most have been near cloud-free.

    In another day or two I'll turn the Stenner back on -- at one pint/day (my timer has 15 min increments, so one 15 min interval) and watch to see how the FC reacts.

    If I can keep the pool going on 1-2 pints of 10%/day (which costs me $3.70 for 2.5 gal) that becomes downright economical....

    thanks for the help -- especially in the early days when I kept adding 2.5 gal jug after 2.5 gal jug and the chlorine would just disappear in hours.

    geoff
    12500 IG plaster/exposed aggregate, resurfaced 2004, 3 jets, waterfall, kreepy krawly in vacuum port, 100 sqft cartridge filter, solar heat, trying to convert to BBB, single speed 115V/14.8A pump, borate

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