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Thread: Green algae returns after draining pool

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    Join Date
    Aug 2014
    casa grande,AZ

    Green algae returns after draining pool

    All last summer was spent fighting green and black algae. Pool water was 6 years old so we drained it during the winter. This summer began like a honeymoon with little chemicals needed to say within the limits. Salt water pool with Hayward equipment. Green algae returned about 3 weeks ago. This weekend we are shocking the pool. What I have noticed is that the green was growing at the base of the pool skimmer grout around the tile.

    We have a sheer waterfall that is not used routinely. I am wondering it the green algae could be growing in there? We live in AZ and I test the water weekly. I have been pretty vigilant about getting the leaves and flowers from my neighbors tree out of the pool. I don't understand why this brand new water is doing this...again.. Oh yes the chlorine has been right on or high so don't tell me to increase that.

  2. Back To Top    #2
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: Green algae returns after draining pool

    Welcome to TFP!

    You don't want to hear it, but you need more chlorine. If your chlorine was high enough, you would not have algae. It may be dropping only for a short time, but that is enough to allow algae to get started. It may be dropping because you don't have enough CYA or you may have so much CYA that the chlorine isn't effective.Post some actual test results with your typical FC and CYA levels.

    You should turn your waterfall on daily to keep it clean.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  3. Back To Top    #3

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Green algae returns after draining pool

    Oh yes the chlorine has been right on or high so don't tell me to increase that.
    Welcome to the forum. Sorry, but your chlorine has been too low.

    We always suggest to read "The ABC's of Pool Water Chemistry" up in Pool School.........that'll get you a better understanding of your pool water.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4
    Mod Squad tim5055's Avatar
    Join Date
    May 2014
    Columbia, SC

    Re: Green algae returns after draining pool

    As John & Dave have pointed out, if the chlorine level was OK algae could not grow. The suggestion to read "The ABC's of Pool Water Chemistry" is a good one as it is our goal here to provide you with the knowledge to control your pool.

    My first question would be is the age of the salt water chlorine generator. Is it original to the 6 year old pool? If so at six years it may be getting near the end of its life and becoming erratic in its chlorine production. Testing once a week gives it plenty of time to have issues on the other six days without your knowledge.

    While on the subject of testing a comment and question.
    * You should really be testing every day, if only to check the chlorine level and pH

    * What test kit are you using?

    To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. If you don't already have one, you will need to pick up one of the recommended test kits. All the kits on the list contain the FAS/DPD test while very few other kits do. The kits sold at the pool store generally won't won't cut it, but be careful pool store employees are known to say “it's the same thing”. Generally it's not!

    The knowledge you need is condensed in the Pool School link at the top of every page.

    It is a great community here, but we do ask that you read and try to understand the information being taught. Questions are always welcome and folks will try to direct you and teach you the methods.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

  5. Back To Top    #5

    Join Date
    Jul 2014
    Bastrop, Louisiana

    Re: Green algae returns after draining pool

    Greetings Bbarth,
    Believe in what John, Dave and Tim are suggesting, their combined experience just on this forum solving problems for others is almost 15 years (adding up their forum join dates).
    In all of the posts i have read (I read about 1-3 hrs a day and I lurked around in the shadows for about 4 months before joining) they have never steered anyone wrong.
    I would be willing to bet (it would be a sure bet) that they could tell you the problems you will experince before they happen.

    The first thing that comes to mind reading your post is how do you come by your test results?
    Second thought, What are those test results?
    Randy H.

    Intex 18' X 48"
    G.A.M.E. Sandpro 75 Sand Filter (Single Speed 3/4 HP, 75 lbs sand, 2650 GPH, 7-way valve)

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