Brown Algae Won't Come Off Of A Vinyl Liner

by Joanne

Opened our pool 2 weeks ago we used liquid shock. The pool water is clean but the liner is covered it what appears to be brown and red algae.

We treated it with a super algeacide and pH balance. The red algae seems gone, but the brown will not come off even after scrubing with a brush. We have never had this problem before, totally have tried everything and don't know what to do.

Thank you

Thanks for the question Joanne

You need to determine if the stain is organic or a metal stain. Using a Trichlor tablet, hold it on the stain for about 3 - 5 minutes. Use a stick or a pool pole, not your finger.

If the stain lightens up or disappears, it's organic. Go to this page to see how to treat your pool for brown algae:

Brown Algae

You can also use about 1/2 lb. of calcium hypochlorite (granular chlorine) in an old sock to put on a spot. If the stain doesn't lighten up, gets darker or the color changes to black, it's probably a metal stain.

To confirm it's a metal stain, get a Vitamin C tablet (crushed up acsorbic acid), put that in a sock, and place it on the stain. If the stain is removed, you can treat the pool with ascorbic acid.

Ascorbic acid treatment:

Things to remember and understand:

  • You must have a good test kit. The Taylor K-2006 works very well. Test strips won't work.

  • Stains are not in the water, they're on the pool surface

  • You're removing the stains from the surface, not the water

  • A metal sequestrant doesn't remove metals from the water. It keeps the metal in the water to not stain the surface. An HEDP sequesterant is best.

  • Be sure your calcium hardness is below 300 ppm and the CYA is not above 70 - 80 ppm. If you find that one of those readings are high you'll need to do a partial drain and refill to get the hardness to 150 - 250 ppm and the CYA at 30 - 50 ppm.

  • Don't confuse citric acid with ascorbic acid. It's cheaper but less effective.

    The Treatment:

  • Put your chlorine down to zero. Any excess chlorine will eat up the ascorbic acid and you want as much acid to go to the stains as possible. Use a PolyQuat 60 algaecide during the treatment.

  • You'll need 1/2 - 1 lb. of ascorbic acid per 10,000 gallons. Start low and work you way up before adding more. Go no higher than 7.2.

  • Put the filter on "CIRCULATE".

  • Broadcast it around the perimeter of the pool. Be sure to get the sides as well.

    Allow the filter to circulate for about 1/2 hour.

  • If all the stains are not gone, leave the filter in "CIRCULATE" and add more ascorbic acid where the stains are.

  • The acid will decrease the pH. Use 1/2 box of 20 Mule Team Borax per 10K gallons. Add slowly to the skimmer with the pump running.

  • Keep the filter in "CIRCULATE" until the stains are gone. Bump up the dose by 1/2 lb. each time.

  • Use a soft nylon brush to loosen up any algae.

  • When the stains are gone, you can use a metal sequestering agent. Metal sequestrants that are based on HEDP, phosphonic acid
    or something similar are the most effective. Jack's Magic Blue, Purple, and Pink Pink Stuff, Metal Magic, Metal Free, & Metal Klear are very good.

  • Put the filter back on "FILTER" and leave it on 24/7.

  • An ascorbic acid treatment might decrease your pH and alkalinity. After filtering for 24 hours you can rebalance the water.

  • Start with the pH and alkalinity. You can use baking soda for both the pH and alkalinity or use 20 Mule Team Borax just for the pH.

  • Test between adjustments and be sure your pH doesn't get above 7.2ppm.

  • If the alkalinity is between 80 - 100ppm, use 20 Mule Team Borax to raise the pH.

  • Now adjust your chlorine. Do this SLOWLY and only use liquid pool chlorine and/or unscented bleach. Powder and/or granular chlorine (calcium hypo) will increase the hardness and the pH level. It will take alot of chlorine to bring the level up in your pool.

  • And get your CYA between 30 - 50ppm. You can use Dichlor for this if it's below 20 ppm. It's a stabilized chlorine that will add CYA to the pool, but the CYA can get out of hand quickly, so be careful. Test after each application.

  • While your raising the chlorine you'll want to watch for developing stains.

  • Keep the pH on the low side, about 7.2ppm and add another bottle of sequestrant and PolyQuat 60.

  • Don't shock the pool for 2 weeks and keep the pH at 7.2ppm for about 1 week. The ascorbic acid and sequestering agent will probably keep it there anyway.

  • Once the chlorine holds for a couple of days you'll know that the ascorbic acid is gone. Go ahead and balance out your pool.

  • If stains appear again, take the pH down to 7.2ppm and give your pool another shot of sequestering agent.

    Here are links to the pH and alkalinity pages:

    Swimming Pool pH Levels

    Pool pH

    Pool Alkalinity

    Total Alkalinity

    Hope this helps and good luck with your pool.


    Question: Is This Brick Dust Or What?
    By: Rosemary

    Hi, I have a greenish stirred up pool. Overnight it settles and at the bottom looks like brown brick dust.

    As my neighbour's just built a brick wall I think it's this and presumably the filter can't cope as it's too fine. Vac it normally - disaster, can't see the bottom. Vac to waste when settled - still can't get rid of it and when filter on still awful.

    Have put in a clarifier and tried to clean it to waste loads of time - losing water and heat. Don't lnow what to do now?

    Any ideas. Frustrated pool owner of England!

    Thanks for the question Rosemary

    I'd like to have your complete chemical readings:

    Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper). It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

    You can get this done at your local pool store.

    Without these numbers I'm just guessing at what the problem is.

    We need to find out whether the problem is algae (orgaic matter) or mineral. You would clear the pool up differently. If it is dust and dirt coming off your neighbor's brick wall, that needs to stop. But first let's get the readings.



  • Comments for Brown Algae Won't Come Off Of A Vinyl Liner

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    Jun 14, 2015
    Brown Tannins Possibly Magnese
    by: Lindsey

    Need help getting brown streak tannens off deep end pool vinyl liner 15000 gal. Tried metal testing. Didn't respond. Have huge redwood tree in neighbors yard :(

    Thanks for the question Lindsey

    I'd like to have your complete chemical readings, the actual numbers:

    Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper) and names of any algaecides you may have used along with clarifiers, phosphate removers, and/or flocs. It makes troubleshooting much easier.

    It sounds like an organic stain. Place a tab on an affected area for 1 minute then remove it. If the stain lightens up it organic and you'll need to shock the pool with liquid chlorine. Get the pH to 7.0 - 7.2. It's 12 oz. per 10k gallons to reduce the pH 0.2. Use 2 gallons of chlorine to increase the FC to 12ppm. Sweep well to mix it up and sweep the affected areas. Maintain a FC of 12ppm until the stain is removed. Be sure your filter is perfectly working.

    If you feel your situation is more complex than this, I do phone consultations. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias.

    Pool Consultation

    Swimming Pool Care eBook

    How To Clear Up A Green Pool eBook

    Swimming Pool Resources

    Hope this helps and have a great Summer.


    Jun 09, 2018
    Vinyl Intel above grounder pool
    by: Cindy

    Hi. We have a 12×24×52 -Intex pool. Over winter the pool got very green, so green you couldn't see the botton. We decided to drain the pool, but now we have green stains that we cant remove. We have scrubbed them with a brush and they won't go away.
    What should we do before we refill with water?

    Hi Cindy. You can remove the stains as best you can with a diluted mixture of chlorine and water, 6:1 in a spray bottle. 6 water to 1 chlorine or bleach. If it's organic stain from algae it can be removed, somewhat, but but might not be perfect. You may want to do this on a test area first as it might bleach out the liner somewhat.

    Most of the time organic stains are removed during the shocking process. Or in the case with plaster pools, a chlorine or acid wash might be needed.

    For bad stains, don't look for perfection. If you get it, that's great, but you don't want to jeopardize the liner in pursuit of perfection.

    Remember you cannot acid wash a vinyl pool. If you're going to use the diluted method, be mindful of bleaching out the liner as was stated above. Using chlorine is the only way to remove organic stains.


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