Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 15 of 15

Thread: What in the heck is eating my chlorine!

  1. Back To Top    #1

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    What in the heck is eating my chlorine!

    Pool is at about 30cya. I always run pretty consistent, SWG running at 40% 10 hours a day (enough to put roughly 2ppm of chlorine a day in the pool). After the pool store guys who did some work left the SWG unplugged for a week, I got something growing.

    I've been SLAMing it for a few days now and I've never had issues like this before. My water is absolutely crystal clear right now, but whatever is going on is chewing through chlorine something fierce.

    Now here's the weird part...
    I thought I had this licked...yesterday evening it was at 9. I put a gallon of 12.5 in and ran the pool for an hour to mix it up good (I actually just noticed the pump 24/7 thing in the slam article - never had to do that before). Anyway, that should have got me to about 17, but I measured 15. Figured okay - we'll just see. This morning I got 15.5. A little odd, but maybe I miscounted last night. Sounds like we're home.

    I left the SWG up at 60% and let it run today - that should put me at an extra 3ppm for the day. Now it was a hot sunny day today and we swam this evening. Sun goes down and I test the water. It's at 7ppm!! Holy cow! Even if I lost everything for the day to the sun, that's still another 8 gone.

    I didn't get any more bleach because I thought we were done. So at this point...
    Should I run the pump overnight with SWG to see where we end up?
    This seems pretty aggressive to me - certainly I've never had anything chewing it up like this - is this not unusual for others?
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

  2. Back To Top    #2

    Join Date
    May 2015
    Location
    Fullerton, CA
    Posts
    622

    Re: What in the heck is eating my chlorine!

    Sounds like there is a bloom still active?
    33x19, 3'4"-5'6", 7ft spa, baja reef, 14'x9', 18" deep, 10,668 Gal. Quartzite coping, Stonescape Tropics Blue mini-pebble, abalone & glass beads. Jandy Equip.(JXi heater, 2.7HPVS pump, PLC1400 SWG, CV580 filter, Aqualink, LEDs)
    TF-100, Doheny Discovery robot.

  3. Back To Top    #3

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    Re: What in the heck is eating my chlorine!

    Quote Originally Posted by Titan7 View Post
    Sounds like there is a bloom still active?
    Or a new one somehow? Last night I was under 0.5 CC, has less than 1fc drop. Yet today it went nuts. Bizarre to me...
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

  4. Back To Top    #4
    Mod Squad kimkats's Avatar
    Join Date
    Jul 2012
    Location
    Tallahassee, FL
    Posts
    26,678

    Re: What in the heck is eating my chlorine!

    Time to start looking with a toothbrush in your hands. Do you have a light? steps that stick out? Have you looked around your skimmer face and behind the door? around the returns?

    Have you been brushing your pool? That is very important to get it all up and in the water for the FC and filter to work on.

    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

  5. Back To Top    #5

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    Re: What in the heck is eating my chlorine!

    Let it run all night (with SWG on) and FC was right at calculated values and CC was only 0.2. I'll stop for more chlorine on the way home and keep my fingers crossed.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

  6. Back To Top    #6

    Join Date
    May 2016
    Location
    Huntsville Alabama
    Posts
    16

    Re: What in the heck is eating my chlorine!

    Definitely been fighting an issue similar to yours. Had a bad algae bloom that just wouldn't go away. Finally got the algae killed but my chlorine levels are still in the tank. I finally ordered a decent test kit and realized I had no CYA in the pool (could see the black dot clear as crystal with the tube full). If you're getting a lot of rain or anything to dilute your water. I'd keep an eye on your CYA just in case.

  7. Back To Top    #7

    Join Date
    Aug 2015
    Location
    Orlando
    Posts
    113

    Re: What in the heck is eating my chlorine!

    30 cya seems pretty low for salt water pool
    Phil
    ~9600 gal gunite pool, NEW July 2015; Pentair Intelliflo 2 VST pump; Pentair C&C 150 filter; Pentair Intelliclor IC40 swg; solar heat w/ Pentair Solartouch controller, screened. Taylor K 2005 test kit, FAS-DPD separate test, Taylor K1766 salt test

  8. Back To Top    #8

    Join Date
    Jul 2015
    Location
    Tempe, AZ
    Posts
    193

    Re: What in the heck is eating my chlorine!

    I've seen my pool use upwards of 8 ppm FC on hot, sunny days when my CYA got down in the 20-30 range (unknowingly) and I was still trying to keep target FC in the 50-60 range. The higher the FC gets, the more is exposed to UV degradation and not protected by CYA.

    I'm not saying that you don't have something growing. But with a CYA of only 30, FC in the 15 range will get chewed up very quickly by the sun.
    John - 16,000 gallon | in ground | pebble | Triton II sand filter | TF100 | speedstir | Hayward Phoenix 2x

  9. Back To Top    #9
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,994

    Re: What in the heck is eating my chlorine!

    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  10. Back To Top    #10


    TFP Guide

    kcindc's Avatar
    Join Date
    Sep 2011
    Location
    Fairfax, VA
    Posts
    1,272

    Re: What in the heck is eating my chlorine!

    Can you please add your location (city and state) to your profile. It can help us steer you to an appropriate CYA level and help with regional water issues.
    Karen
    33K IG w spa plaster, Pentair 1HP Whisperflo, DE Filter, SWG CircuPool RJ-60, Dolphin Triton Plus, Raypak Dig 336K BTU, TF-100.
    Pool Math Chlorine / CYA Chart SLAM - Shock Level And Maintain
    2017 replaster/retile

  11. Back To Top    #11

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    Re: What in the heck is eating my chlorine!

    I normally run really well at around 60-70 cya. Then after a week with my SWG off, my chlorine was gone and my cya was half what it was - I never actually paid close attention to CC, but I figure there was some bacteria in there and it chewed up my CYA Anyhow, I figured I'd shock at that level anyway (easier to get to shock levels and too long or expensive to get CYA up).
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

  12. Back To Top    #12


    TFP Guide

    kcindc's Avatar
    Join Date
    Sep 2011
    Location
    Fairfax, VA
    Posts
    1,272

    Re: What in the heck is eating my chlorine!

    CYA normally doesn't reduce on its own and is reduced whenever your replace water like during backwashing, large amount of rain with overflow or splash out. I believe it usually degrades at the rate around 1 ppm per month.

    When a large amount of CYA disappears it is converted into ammonia and happens during the winter months with really cold water. This typically happens when the pool is close in northern climates.

    CYA should be tested once a month or more frequently if you've had to replace a large amount of water.
    Karen
    33K IG w spa plaster, Pentair 1HP Whisperflo, DE Filter, SWG CircuPool RJ-60, Dolphin Triton Plus, Raypak Dig 336K BTU, TF-100.
    Pool Math Chlorine / CYA Chart SLAM - Shock Level And Maintain
    2017 replaster/retile

  13. Back To Top    #13

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    Re: What in the heck is eating my chlorine!

    Quote Originally Posted by kcindc View Post
    CYA normally doesn't reduce on its own and is reduced whenever your replace water like during backwashing, large amount of rain with overflow or splash out. I believe it usually degrades at the rate around 1 ppm per month.

    When a large amount of CYA disappears it is converted into ammonia and happens during the winter months with really cold water. This typically happens when the pool is close in northern climates.

    CYA should be tested once a month or more frequently if you've had to replace a large amount of water.
    I measured it about a week or two before the SWG was left off. It was at 60. And I sure didn't replace half the water in the pool. So something ate it pretty darned quick.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

  14. Back To Top    #14


    TFP Guide

    kcindc's Avatar
    Join Date
    Sep 2011
    Location
    Fairfax, VA
    Posts
    1,272

    Re: What in the heck is eating my chlorine!

    Can you verify if you did the CYA test correctly? It is very finicky and light sensitive. Full sunlight, back to the sun, vial waste level with two fingers. Pour to 100, check for the dot, pour to 90 check for the dot, etc.

    The only way to go from 60 to 30 is by replacing water. Did you have some heavy rain storms? Do you have an autofill? Could you have a leak?
    Karen
    33K IG w spa plaster, Pentair 1HP Whisperflo, DE Filter, SWG CircuPool RJ-60, Dolphin Triton Plus, Raypak Dig 336K BTU, TF-100.
    Pool Math Chlorine / CYA Chart SLAM - Shock Level And Maintain
    2017 replaster/retile

  15. Back To Top    #15

    Join Date
    Aug 2011
    Location
    Northville, Mi
    Posts
    307

    Re: What in the heck is eating my chlorine!

    Quote Originally Posted by kcindc View Post
    Can you verify if you did the CYA test correctly? It is very finicky and light sensitive. Full sunlight, back to the sun, vial waste level with two fingers. Pour to 100, check for the dot, pour to 90 check for the dot, etc.

    The only way to go from 60 to 30 is by replacing water. Did you have some heavy rain storms? Do you have an autofill? Could you have a leak?
    Been testing it consistently the same way for years. No autofill, no leak. Had some rain, yes, but not enough to lose half my CYA. Bacteria can eat it faster than just over the winter, given the right conditions...I reference chem geek's post and my own experience...
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4

Posting Permissions

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