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Thread: Dirt/Algae at bottom of pool

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    Dirt/Algae at bottom of pool

    This is my first posting but I’ve been lurking on this site since the beginning of the summer and its been extremely helpful. I’d like to thank the board for all the information I’ve gleaned.

    I have a reoccurring problem. I started the summer with a green swamp but I was able to clear it using the information on the “Turning Your Green Swamp Back into a Sparking Oasis” posting. Unfortunately I’ve had at least four algae blooms since then, despite what I feel is good maintenance practices. Each time I had to clear the algae I followed the same process and each time I got the water clear again but it doesn't stay clear for long. I keep my chlorine levels above what I have in the previous years but it doesn’t seem to help. The algae can be best described as a light brownish/green silt at the bottom of the pool. Sometimes there is a little on the side. When you brush it it is almost as though it’s just a very light dusting of dirt. In fact that’s what I thought it was on two occasions and my first response was to vacuum it, and/or vacuum it to waste. As it clears I continue to brush over the next couple of days and life is good again. A couple of weeks later the stuff reappears at the bottom of the pool. I begin to brush but then it just mixes in the water and the water becomes a murky green and I have to start all over again.

    I'm not sure if this is significant but I had a leak earlier in the summer and after some time found the hole in the liner and patched it. There are about four more very small “knicks’ in the liner (my son and his friend were practicing their casting into the pool with a bolt on the end of the fishing line!) but they're so miniscule water doesn't leak from them.

    As of mid day today the pool is clear and these are my readings

    FC 5+
    TC 5+ (My Leslie's pool kit only reads to 5)
    CC 0??
    Ph 7
    TA 60
    CYA 50
    CH 40

    thanks
    20K gal, vinyl, 3/4 HP pump, Hayward sand filter

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    JasonLion's Avatar
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    Re: Dirt/Algae at bottom of pool

    Welcome to TFP!

    With a CYA of 50 you want to keep your FC level at 4 or higher at all times. That typically means rasing FC to 7 or 8 in the evening, so it will still be at least 4 the next day. If you haven't been doing that, then that is why you are getting algae over and over.

    It isn't related to the algae issue, but your TA is on the low side. You will want to raise it a little fairly soon.
    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

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    Re: Dirt/Algae at bottom of pool

    Welcome to TFP!!

    This smacks of 'Matt's Mud" or "4X4 Algae" I'll give the link in a moment.

    This is a persistent type of algae that should be treated as mustard algae.

    this thread mentions it and links over to the post on PF where I named it
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    frustratedpoolmom's Avatar
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    Re: Dirt/Algae at bottom of pool

    I'd start checking all the little nooks and crevices where it could be hiding in poor circulation, just waiting for the right moment for the FC level to drop a bit and it can come roaring back. Make sure toys, ladders, light niches, etc. are checked, suits/towels laundered before re-entering the pool.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Dirt/Algae at bottom of pool

    Thanks guys. Waste I found the link thanks. Interestingly I too have the discolorations in my liner that the other post discusses. I will reread it and follow the suggestions. My pool is clear this morning but when I brush it, it still kicks up that very faint dust like algae. I"m going to keep it at shock level.

    I'm always learining something here. I knew algae could hide but I didn't know it could be carried back in by swimsuits!
    20K gal, vinyl, 3/4 HP pump, Hayward sand filter

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    frustratedpoolmom's Avatar
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    Re: Dirt/Algae at bottom of pool

    Yup. Especially if one has been swimming in a natural body of water and then returns and hops in the pool!
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Dirt/Algae at bottom of pool

    Arrrgh!! I'm still having trouble. Here are my readings:

    FC 13
    TC 13
    CC 0
    PH 7.0
    Alk 40
    cya 45

    I know the Alkalinity and PH are low so I'm about to raise them to the proper range, but this algae thing won't go away. I shocked and cleared all algae two weeks ago. Since then I've kept the chlorine high. Usually around 11-12. I kept it high because it was high after shocking it and it came down slowly because I continued to add a little chlorine each day. I figured better safe than sorry. Things were ok, but at the end of last week I began getting that very light 'dusting' of algae on parts of the bottom, and a greenish ring around some portions of the sides. I'm going out to brush right now, but how can the algae return if I'm keeping the chlorine so high? Even if I missed a bit when I shocked, the continual high chlorine level should have prevented any algae from getting a foothold, shouldn't it have? Should I shock now, or just bump it up a bit?
    20K gal, vinyl, 3/4 HP pump, Hayward sand filter

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    JasonLion's Avatar
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    Re: Dirt/Algae at bottom of pool

    How confident are you that CYA is really around 45? Do you have your own test kit, test strips, or is that a pool store number? Have you been using any trichlor tablets or dichlor "shock"?

    Assuming that your CYA level really is 45, there isn't much of any change of getting algae with FC levels around 13. Could the "algae" actually be dirt or pollen?
    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

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