Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 11 of 11

Thread: Algae with ~0 ppm CC?

  1. Back To Top    #1

    Join Date
    Jan 2015
    Location
    Tampa Bay, FL
    Posts
    16

    Algae with ~0 ppm CC?

    I let my pool get green over winter. Bought some magic Algaecide potion from the pool store, additionally applied some 1-2 lbs of powder shock at the time and within a day or two all green was gone and had turned into gray matter. Cleaned filter, backwashed a few times and all was good. That was back at the end of February.

    Ever since then, I've been maintaining and monitoring the chemicals in my pool quite diligently. Never let FC go below 7.5% of CYA.

    And yet, a couple of days ago, I got a faint film of algae in the deep end. How's that possible with a steady 0-0.5 ppm CC over the past month+ and FC within tolerances relative to CYA?

    CYA level is quite volatile due to a leak, that I estimate somewhere between 500-1000 gal of water per week. I have an autofill device that keeps my pool water level topped off at all times. So, CYA is a consumable for me and I add about 2 lbs of it every 10-14 days. I use liquid chlorine (10.5%) for sanitizing. CH, TA, and pH keep in check all by themselves, so I don't have to do anything about them. I only add CYA and liq. chlorine.

    Full disclosure: I don't scrub my pool walls as often as I should, maybe once a month. Could that be a reason for the green film?

    My last pool test results were:

    FC: 5.25 ppm
    CC: 0.5 ppm
    CH: 200 ppm
    pH: ~7.7
    TA: 120 ppm
    CYA: 40 ppm
    Water: 24C (=75F)

    [Oh yeah, in case you're wondering: the 5.25 ppm FC test result is correct. I double my water sample size to 20 ml for the FC/CC test, so each reagent drop counts as 0.25 ppm.]

    My test results over the past weeks since reopening my pool in February are available as an interactive graph (courtesy of Google Sheets). Note that two y-scales are used and some of the values have to be multiplied by 10 (water C and CYA ppm). Only CA and TA use the right y-scale.

    The saber tooth curves of FC at the end of Feb/beginning of March reflect an additional test three hours after adding chlorine to give me an idea of chlorine usage per day. Only one more test in March (on the 21st) was like that. All other FC readings were taken at around 6 p.m., the lowest reading for that day, immediately before adding chlorine.

    I always add 0.5 gal chlorine per day (these appear as faint green bars in the graph), but skip a day if the FC result is high enough. Stabilizer added appears as a red bar, and so far I've been adding it in 2 lbs doses.

    The recent rapid drop in CYA from 70 ppm to ~45 ppm within just two days at the end of March has me puzzled. Could that have been from the rain?
    Attached Images Attached Images
    17,700 gal fiberglass outdoor, rectangular, chlorine-sanitized in-ground pool, 35x15 ft2. Pentair FNS Plus D.E. Filter (48 ft2). Pentair Whisper Flo 4 (1 hp) pump. Two skimmers (@2- and @4-), two returns (@7- and @10-), one vacuum (@4-o'clock position skimmer), no main drain. Autofill device adding ~1000? gal of utility water per week. TF-100 test with speed stir.

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Algae with ~0 ppm CC?

    Well, I think your problem comes down to the fact that it does not look like you followed and completed the ShockLevelAndMAINTAIN Process to ensure that you had eradicated the algae.

    Confession ... I bet I brush less than you and I have not had any algae in years.

    Dealing with the fluctuating CYA is certainly going to be a pain, but I would recommend going through the SLAM process now and then ensure the FC never drops too low.

    Also note, that it is possible to have CC or algae and not the other ... they can be fairly independent of each other. That is why there are 3 criteria to ending the SLAM.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  3. Back To Top    #3

    TFP Guide
    PAGirl's Avatar
    Join Date
    Jun 2012
    Location
    Central PA
    Posts
    2,388

    Re: Algae with ~0 ppm CC?

    Could the circulation of the water in the area of the algae be poor?
    26' X 52" Intex Ultra Frame. Intex Sand Filter
    26' X 52 Intex Ultra Frame Install
    You can lead a horse to (clear) water, but you can't force him to swim in it!

  4. Back To Top    #4
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,999

    Re: Algae with ~0 ppm CC?

    Last summer I had some algae with perfectly clear water, no CCs ever and what I thought was always plenty of FC, even on the hjgh side, usually above target. I also was a slacker in the brush department. A week or so of FC close to shock level and daily brushing while swimming took care of it. Now I try to brush at least a couple of times a month.

    The low level of FC that may have occurred would account for your CYA being consumed by bacteria as well. Unless you had about 40% of your water volume replaced by rain overflow.
    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

  5. Back To Top    #5

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,085

    Re: Algae with ~0 ppm CC?

    I believe brushing is an essential part of pool care. Almost daily during a SLAM and once or twice weekly as normal maintenance.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  6. Back To Top    #6


    TFP Guide

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

    Re: Algae with ~0 ppm CC?

    Do you know where your leak is located? If you have a leak at the skimmer level or below, or somewhere in the below ground pluming, I'm assuming you would be introducing organics as soon as the pressure drops when the pump is off which can increase the chlorine demand.
    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

  7. Back To Top    #7
    Casey's Avatar
    Join Date
    Apr 2007
    Location
    SW PA
    Posts
    10,157

    Re: Algae with ~0 ppm CC?

    Quote Originally Posted by duraleigh View Post
    I believe brushing is an essential part of pool care. Almost daily during a SLAM and once or twice weekly as normal maintenance.
    Brushing is the number one pool chore that is never done enough.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

  8. Back To Top    #8

    Join Date
    Jan 2015
    Location
    Tampa Bay, FL
    Posts
    16

    Re: Algae with ~0 ppm CC?

    Thanks everyone for your answers and tips.

    • @jblizzle. Right. I did not SLAM my pool when opening in February. Is there reason not to believe in an algaecide product to do its job, though? So, is it possible that since February I've had something in my pool that causes algae to grow, even though my FC level never dipped below 7.5% of my CYA level and my CC level never exceeded 0.5 ppm in the same time frame?
    • @PAGirl. I don't know if circulation is poor in the deep end. How do I measure that?
    • @pooldv. I don't think 40% of my pool water volume was replaced by rain. That would be several feet of precipitation. Don't think we had that much rainfall lately. Besides, it seems that my leak causes more water to disappear the higher the water level is, so I would think that rain water would be the first to leak, rather than established (i.e. chemically treated and balanced) pool water. CYA can get eaten by bacteria so that it can drop by 25 ppm within two days? With a CC level that never exceeded 0.5 ppm in the past month and a half?
    • @duraleigh. If I had brushed twice a week, I probably would have never seen the algae and known that there was a problem with my pool water. If I were to never brush my pool, would it be inevitable that algae form, even if FC and CYA were kept in check at all times?
    • @kcindc. I have no idea where my leak is. What I've noticed though, is that if I set my autofill device to a level that's at or above half of the skimmer opening height, I tend to lose unproportionally more water than at 1/3 the height of the skimmer opening, which is where the autofill level is currently set to. Explain to me where those organics would come from and what they would be? Could it be anything other than soil? So, soil causes chlorine to be consumed?

    So, meanwhile I did the overnight FC loss test. At 9 pm last night I had an FC level of 8.25 ppm. This morning at 6 am it was at 7.5 ppm. So, that's a loss of 0.75 ppm over night. (The water was not circulating at both times or in between though). CC was 0.25 ppm last night at 6 pm. Other than the visual cue of algae from a few days ago would there be any reason to SLAM my pool at this point? Is that a reason at all anyway? If I had brushed once or twice weekly, I would have never seen the algae and given my test results I don't see any other indicator that would warrant a SLAM. My water is crystal clear. My CC level never exceeded 0.5 ppm since my pool opening at the end of February.

    Besides, what are the indicators to SLAM anyway? I see the conditions for stopping a SLAM (CC <= 0.5 ppm, OCLT pass, clear water). What are the conditions requiring a SLAM though? The opposite condition of any one of them? None of these occurred for me though.
    17,700 gal fiberglass outdoor, rectangular, chlorine-sanitized in-ground pool, 35x15 ft2. Pentair FNS Plus D.E. Filter (48 ft2). Pentair Whisper Flo 4 (1 hp) pump. Two skimmers (@2- and @4-), two returns (@7- and @10-), one vacuum (@4-o'clock position skimmer), no main drain. Autofill device adding ~1000? gal of utility water per week. TF-100 test with speed stir.

  9. Back To Top    #9
    Mod Squad kimkats's Avatar
    Join Date
    Jul 2012
    Location
    Tallahassee, FL
    Posts
    26,740

    Re: Algae with ~0 ppm CC?

    I do an OCLT about once a month just to keep an eye on my pool and make sure this does not happen.

    I will tell you what happen with my pool though..........my husband's only job with the pool is to brush the sides at least twice a week. Well he got a little lazy with it "It looks fine". Well after two weeks of him not brushing the sides (the ONLY thing that changed during this time) I noticed a slight green patch in a couple of areas on the walls. I called him out to the pool and brushed the sides and a green cloud went into the water Humm I wonder why that is?? He jumped in right then and there and brushed the sides of the pool! We have not had that problem again. LOL

    My OCLT had shown something was going on as I lost more FC than normal so I KNEW something was up. That is what made me look closer. I did a SLAM but it did not take long as I caught it so early.

    Let us know how things are going.

    Kim
    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

  10. Back To Top    #10
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,999

    Re: Algae with ~0 ppm CC?

    Yes, bacteria can consume CYA very quickly. Algae can occur in low water flow areas and can form a protective barrier to the chlorine. Brushing stirs up the water in low circulation areas and also exposes the algae to chlorine. So, brushing most likely would have killed the algae before you ever saw it.

    Some indicators of a need to SLAM are cloudy water, green water, visible algae in the pool, failing the OCLT, high CC. Since you only have one of these you might get away with not SLAMing but I would still be diligent about brushing and raise your chlorine level for a while.
    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

  11. Back To Top    #11

    Join Date
    Jun 2014
    Location
    Rogers, AR
    Posts
    412

    Re: Algae with ~0 ppm CC?

    I am a huge brusher. I believe that it makes all the difference. I even brush while my robot is running.
    16x32 IG rectangular 21,800k new vinyl liner 2014, Triton II TR 50 sand Filter, Pentair 3/4 hsp whisperflow pump, 3 returns, TF100 test kit w/speedstir. Maytronics s 300i robot.

Posting Permissions

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