Pool Liner Stained From Acidity Too High

by Clare
(Narromine NSW AUstralia)

I have been running our pool with too much acid. It's has stained the liner and plastic components of the pool a brown colour, especially at the water line.

What can I use to fix it now that I have the pH balanced?

Thanks for the question Clare

There are basically three kinds of stains:

Biological (algae, pollen)

Chemical (acid, chlorine)

Organic (grass clipping, leaves)

In your case the question mentioned running the acid too high which will lower both your alkalinity and pH.

Swimming Pool Supplies

For a brown chemical stain like yours, the best solution would be to use granular ascorbic acid. Add 1 lb. of granular ascorbic acid per 10,000 gallons of pool water. I think in Australia you use the metric system so that would be about 0.45kg or 453 grams.

Mix the ascorbic acid in a bucket of water. Slowly pour mixture around the perimeter of the pool. Turn on the pool filter for 8 - 10 hours. Recheck the pool liner to see if the stains have disappeared. Add a metal sequestering chemical, such as Metal Gone, if stains are still visible. Pour 1 qt. of liquid Metal Gone per 15,000 gallons of water directly into the pool.

Turn on the filter for another 8 hours or until the stains have disappeared. It might be necessary to increase the pH after stain treatment. If you have this problem in the future there's an easy way to determine if the stain is mineral or organic.

Fill two white socks, one with chlorine the other with ascorbic acid. Put one of each sock on the stain and check in 3 - 4 hours. If the chlorine starts to lighten the stain, you will know it's an organic stain. If the ascorbic acid works, it's a mineral stain. This eliminates any guessing.

Hope this helps and have a wonderful Summer


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Nov 29, 2012
White Stain Above Water Line
by: graham

I have a 18 month old fiber glass pool. It has just evaporated some water and a white mark has appeared around the pool sides above the water mark.

When I rub this it disappears, but then reappears after 5-10 mins. It has not stained the pool and it does not feel like anything. I have used buffer as advised by my pool shop, magic eraser etc...but to no avail....

Has anyone ever come across this as everyone I speak to are stumped!

Thanks for the question Graham

Without a full set of chemical readings it's a guessing game right now, but here are some things to can look at.

You might be getting metal stains through metal in the fill water. Quality product like Jacks Magic Pink, Blue, or Purple Stuff or Proteam's Metal Magic work very well. Get you water tested for metals.

Keeping a lower pH (7.2 - 7.4) and lowering the TA (70 - 80ppm) may help the stains from reappearing. Metal stains are sensitive to the pH level. Around 7.0 pH it's hard for the metal to stain and above 7.8 is very likely.

Iron can also be present in pool water when you have rusting pats like screws and other metals such as ladders.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

Contact Me


Hope this helps.


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