Swimming Pool Stains Removal Guide
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how to prevent and treat pool stains
Pool stains – yuck! Everyone wants their pool to be without stains. But sometimes those hard-to-remove spots and stains can take a bit more than just brushing. Here’s how you can treat and prevent unsightly swimming pool stains.

The first step to getting rid of those eyesore spots is to diagnose the stain type. Swimming pool stains can be caused by metals in the pool water, rust coming through the wall or by any organic material. The first clue to identifying the type of pool stain is the color of the stain.

A greenish-brown colored pool stain is generally due to something organic – such as leaves or mud sitting in the bottom of the pool over the winter. Algae, worms or other dead animals can also leave an ugly stain on your pool surfaces.

Pool stains that look reddish-brown, are very dark in color, or have a rust-like appearance to them are likely caused by metals. Copper stains in a pool will normally form blue, green, or black stains, while iron may cause rusty, brown, or green-brown splotches, and manganese will cause brownish-black or purple stains.

Berries or seeds can also create a red or blue stain. These are usually no surprise when they originate from plants surrounding the pool, but can be unique if brought in by birds or squirrels.

If this doesn’t help you determine the type, Jack’s Magic Stain ID Kit comes with sample packs of their pool stain removal products to try out on the stain before you purchase a a particular stain remover. Another option is to take a sample of your water to be tested for trace metals that may help identify the stain in your pool.

Organic Pool Stains

A super simple way to get rid of organic pool stains is to shock the pool and give your pool a little TLC with a good brushing. Generally this removes most organic stains in your pool. Pouring a small amount of granular chlorine shock right over an organic stain will usually make it disappear instantly. Works great on plaster pools, but don’t try this to remove stains on a vinyl pool, or you may also remove the liner pattern!

Localized stains can be removed with a device called the Jandy Stain Master and a gallon of muriatic acid. You can also pour acid into a piece of pvc pipe that you hold over a small spot on a plaster surface. Attach a 90 degree fitting on the end to deliver the acid to a stain on the pool wall. If the entire pool is lightly stained however, you may end up with a reverse stain – a bright white spot, surrounded by a darker color.

Stain EraserTo skip the harsh chemicals, consider the Stain Eraser. This product is made of a polymer with a built in mild abrasive to give your scrubbing an extra kick. It also comes with a tile grout scrubber to get in between those fine cracks. There are two different types of heads – one for a concrete pool and the other for a vinyl pool. Attaches to your pool pole to remove those hard to reach pool stains.

If your stain is all around the waterline of the pool because of material floating at the Pool First Aidtop, use an enzyme-based cleaner such as Natural Chemistry’s Pool First Aid. Enzyme-based cleaners help to break down organic compounds and oils by speeding up the chemical reactions that assist in making stains virtually disappear on their own. Follow up with a good brushing again to make sure you’ve got all the left behind debris and oil.

Organic pool stains are not so hard to remove, but over time, it will give your pool a dull light-brown appearance. It’s hard to notice because it happens so slowly. Eventually you may decide to drain and acid wash a plaster pool. This is not something that you can do often, as it involves a purposeful stripping of a thin layer of pool plaster. For some pool owners who want to restore the bright white surface – an acid washing can be a good solution, every five years or so.

Metallic Pool Stains

If you have determined that you have a metallic stain, the first thing to do is to reduce and remove the trace metals in your pool water. One such very effective product would be Natural Chemistry’s Metal Free. This product is especially great at removing iron and copper from your pool, which can be a major issue, especially if you fill your pool with well water. If you just treat the stain and neglect to take care of the imbalance of metals, the stain will just keep returning.


stain-free-bw
A powerful follow up to target stains left by metals is Natural Chemistry’s Stain Free. Stain free is an ascorbic acid based pool stain remover. That’s right – Vitamin C, and it makes a great pool stain remover. Linus Pauling would be so proud!

One way to test if Stain Free would work on your particular pool stain is to grind up a small handful of Vitamin C tablets from your medicine cabinet, and sprinkle these over the stained area. You may be surprised at how well Ascorbic Acid works to remove pool stains!

Any of these products should make current stains disappear and old stains lighten right up if you treat the metals in your pool correctly. If the staining has reached your pool steps and they need an extra scrub, try Jack’s Magic Step Stuff to whiten your pool steps back to brand new condition.

Preventing Pool Stains

To keep organic pool stains out of your pool, do your best to keep the pool clean. This may involve trimming trees or bushes around the pool, investing in a better winter pool cover or an automatic pool cleaner.

Some of the worst pool staining can occur from mudslides or mulch-slides into the pool. For those that find it impossible to correct these conditions, recoating the pool with a dark colored plaster or liner will help to hide the resultant pool stains.

To prevent metallic stains from returning, make sure to regularly test your water for metals using a water chemical test kit, as the stains will keep coming back if you have a highly metallic pool. Metals in your water can come from well-water, or from iron or copper pipes.

A common cause of blue-green copper pool stains is improper chemical maintenance. Low pH and high chlorine levels can also erode the copper heat exchanger in a pool heater. Maintaining proper water balance makes it easier to keep pool stains from occurring in the first place.

Metals are not uncommon in pool water, and they can be hard to remove from the water. Instead of removing the metals, sequester them with a Stain & Scale product. Sequestering agents, also known as Chelators, tie-up minerals in solution – it’s when they come out of solution, floating free in the water, that they can deposit themselves as stains on your pool surface. Two sequestering agents that are especially useful are Super Stain Away or Jack’s Magic Blue Stuff.culator-packet

Metals are not impossible to remove from pool water. If you have severe metallic pool stains in your pool, try CuLator Metal Eliminator. Drop the disposable absorbent bag into your skimmer basket and it absorbs metals such as Copper, Iron, Manganese, Cobalt, Silver, Nickel.

Hopefully these suggestions will help you understand pool stains a bit more and provide some useful methods for effective pool stain removal. A great way to avoid stains before they start is to make sure that you keep your pool clean, your chemical levels balanced, and your minerals sequestered.

Where pool stains are concerned, an ounce of prevention is worth a pound of cure, and in this case, a hassle free beautiful pool!

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sabrina-3
Sabrina Potirala
InTheSwim Staff Blogger


Comments

Swimming Pool Stains Removal Guide — 50 Comments

  1. Hi recently bought a house with a pool. (In Las Vegas and vegas has harsh water) It had the original pump and worked great-crystal clear water and plaster. Needless to say I work out of town and my pool guy went mia as well has the pump broke and by the time I got home my water was green. I hired a new pool guy to acid wash it and service it weekly along with buying a much larger more efficient pump. About a month after it was acid washed there were huge orange stains not only on the bottom but on the walls of the pool..pool guy shocked it, nothing happened then put a stain remover in it still nothing then put yellow treat in it..still nothing then put another stain remover (not sure what it was) an ran the pump for 48 hours straight on high…still nothing I have noticed there are cracks at the bottom now in the plaster and the stains are all still there..pool guy said there’s nothing that can be done unless we drain again and re acid wash or the plaster. Please help as I am so upset and not sure what caused this to happen.

    • Orange, huh? Typically red-orange stains are iron based. if so, there should high iron content in the water still. You didn’t mention trying to sequester the stain back into solution (not sure what ‘stain remover’ was used. Might be a long shot, but balance water, put pH around 7.0-6.8 and add any Stain & Scale treatment like Metal Free or Stain Away. Brush, and if you’re lucky it might be a cheap solution. You could also test the water for iron with iron test strips. Another solution is to use a jandy Stain master over the areas, to acid wash the surface, but underwater. Attaches to pool pole.

  2. We filled out newly white marbelite pool last night. Yesterday it rained and in the shallow end there are muddy spots on the marbelite. We tried brushing and it doesn’t go away. The pool is halfway full so we are carrying on filling today.
    How do I get those marks off on new marbelite? I have a suspicion a child went into pool yesterday and with muddy feet made those marks.
    Will the marks come off new marbelite and what can we do. Desperate please

    • Hi Michele, chances are that they will fade away. I would wet the area, then sprinkle some granular pool shock chlorine to the area (now), or maybe Comet cleanser, then brush and rinse well. If that doesn’t work, you can try a stain remover like EZ Stain or A+ Stain remover, but when water covers the areas. Keep filling the pool, and brush it 2x daily… good luck!

  3. Hi I have a salt water stone pool. I believe its all stone, its taken us a long time to learn the care of one of these pools. (Never had a pool before)we clean it use shock and check the pH levels.
    It’s been very hard keeping it clean and clear because the trees around it.
    Our question to you (because no one can answer us)we have a black and white stain on the outer rim at the water level. We seemed to try everything but sadly no luck. Please HELPPPPPPPPP

    • Hi Donna, water level stains, or bathtub rings, are normally a mixture of dirt, oils, minerals and other stuff. Enzymes are often an effective preventative treatment, especially for oil based rings. If it is more scaly and flaky, and not very oily, you may want to try muriatic acid, diluted 50/50 with water and poured on the wall to see if it bubbles up and scrapes off. Stone pools also can develop efflorescence around the water line, but this is calcium and other minerals leaching from the backside of the pool wall, from water outside the wall, leaching (seeping) thru the mortar. This can also be removed with careful acid washing, a pressure washer can also be used (separately from acid washing), to remove many types of water line stains and scale. All treatments require lowering the water an inch or two, so you can really get at it… good luck!

  4. My problems started when my pool heated sprung a leak. After replacing the heater I was told not to turn it on until I got all the chemicals balanced. So I had to raise the PH level, raise the Calcium Hardness and lower the Cyanuric Acid/Stabilizer. And after taking 3 feet out of the pool and putting new water in the levels were find on Thursday. Then this past weekend my steps have a black stain on my. Today Monday the white cover around my pool lights have a grey film on it. What happen? The water is crystal clear and all the chemical are showing good.

    • Hi, sounds like some metals and/or minerals got knocked out of solution, mixed with dirt and deposited themselves – black and grey stains could be copper or silver, but is likely a mix of many particles. It could have happened if you shocked the pool, perhaps the fill water has high metal or mineral levels. Sometimes such stains fade and disappear again, quickly – but if not, use a sequestering agent like Stain Away or Metal Free to try and absorb the metals back into solution. Then you have to add maintenance doses to keep it active, because it degrades in 1-2 weeks time. Pool Rx may also be a good solution to try and remove some of the metals from the water. If you do have high metals in your fill water, consider also using a Pre-Filter when filling the pool or topping off, to remove metals and minerals, or fill from pre-treated home softener system water. Another treatment is to use our Stain Removers like EZ Stain or Stain Free to hit the spots affected.

      • Hi, yes aside from acid washing a plaster pool, another good way to get rid of pool stains is to just paint over them. Of course you have to paint over the whole pool, or you get a ‘reverse stain’, where there are lighter/cleaner looking ‘stains’. Same thing sometimes happens with using a stain bag or stain master tool, you have to ‘feather’ the stain removal just right, and be precise enough not to end up with a bunch of small white(r) circles around the pool… 🙂

  5. Hi, I have a big dark brown stain at the bottom of the pool just below the steps . The rest of the pool is fine. This is a
    plaster pool with a salt chlorinate. The pool man has tried shock treatment and the other tricks of the trade (no idea what he used) . The stain has been there for a few years and doesn’t appear to be getting bigger. Could it have been caused originally from salt (20kg bags) poured in from the steps? Your advice would be appreciated. Thanks .

    • Hi Angela, adding salt in a single area and not brushing it could cause stains, but usually requires a high pH level at the time, and may also require salt that has impurities, such as solar salt or mined salt that is not purified to remove metals. The typical tricks of the trade are 1) Chlorine, will remove most organics, 2) Acids, will remove most metals/minerals and 3) Sequestering agents, which will absorb suspended metals and minerals in the water, to keep them in solution (to keep them from staining), but may have little effect on stained surfaces, or metals that are already precipitated and deposited. If the area is extremely rough, and the plaster very thin in that area, what you could be seeing is the gunite (concrete) below the plaster, showing through. Not sure if you’ve tried to acid wash the area, but that might be the next step. The Jandy Stainmaster is a device that can deliver liquid acid (muriatic) directly to a source. When placed flat on a surface, a small valve opens to release acid inside of a 3″ diameter cup, attached to your pole. It is very time consuming for large areas, but can handle a few square feet if you have a few hours time. But if it did work well, you may want to drain the pool, at least to below the stain, acid wash the walls and steps and floor area exposed, and then refill, rebalance, and add more salt (to the deep end, with the main drain on Full, and using a brush to push it around). Also have the pool pH in the 7.2-7.6 range before adding salt, and be sure that it is Pool Salt, or Food Grade salt, which go through brining and evaporation to remove impurities like iron, copper, manganese, and contains no Iodine, like some table salt.

  6. We are sick to our stomachs. After playing over $3,000 for a new liner, $400.00 in chemicals to get the pool started back up, the entire liner is green. Been to two different pool stores for solutions and multiple hours of putting in different combos of chemicals, still green, no change at all. Brush scrubbing does nothing. Now what?

    • Hi Kathy, your blue liner has turned green? That’s a new one – I suppose it’s not algae, or algae stains, but I would copper? High levels of copper, with a high pH, can drop out of solution during a shock treatment. If you havent’ tried a sequestering agent, for metals, I would add MetalFree or Super Stain Away, following instructions closely. You can also test the water for the presence of metals, to see what you are dealing with. Jacks’ Magic products has a Stain ID kit and Stain Solution #1, the Iron/copper Stuff that is effective on metal stains. Vitamin C (ascorbic acid) can also often be effective. You can test with crushed up Vit C tablets, and treat with Stain Free

  7. This year our pool has a stain all over this year. yellowish/green. It was a mild winter and was told algae may have taken over the concrete. I have well balanced water but I am lost. Jacks stain kit did nothing. Vitamin C test left a little orange stain but no removal. It has been 6 weeks. Plaster feel a little rough. I have scrubbed with a metal brush- no luck. Pumas stone took some off the easy areas but I can’t do the entire pool with a pumas stone. I know that wear away the concrete also. someone suggest Jacks, Iron Cobalt and etching but when I called Jacks for details they said if the stain kit didn’t do anything not to waste my money. I really believe it’s organic due to the color and winter conditions.But High chlorine didn’t help either. any further ideas?? Thanks.!

    • Hi Sharon, what can sometimes happen is a film of calcium carbonate can settle over the surfaces, locking in algae. Try lowering the pH to 6.5, using a nice test kit like the K-2005 that can do an acid demand and base demand… broadcast pH decreaser over the pool (granular) then brush hard with a steel bristled pool brush, 3 times if needed during one day. If you have a heater or salt cell, leave the pump off for the day (make sure chlorine is a little extra high the morning of…) so the low pH won’t cause problems. If that doesn’t do the trick and remove the stains, you can try EZ Stain Remover, a mild acid granular that is sprinkled over the area.

  8. Hi. A small metal washer sat on our fibreglass pool bottom for a couple of days and left a rust stain. How can this be removed?

    • Hi Richard, you can make a stain sock – fill an old orphan sock (thin, or hosiery), with pH decreaser, or even better, Super Stain Away, with 1-2 cups of chemical, in the sock. Tie the sock off tightly, and cut off excess sock above knot. Push it down on the stain with your pool brush, and hold it there for 30-60 seconds, then remove. Place again if you need more. If very severe, it may need several treatments, but don’t leave it for long, as you may get the reverse, a larger white spot, lol. There is also a device called a Stain Master, which delivers muriatic acid or other liquid acids, thru a hose, directly to a small (3″ dia) cup placed over the stain. Move it around so it won’t over-acid any area. Finally, you can sand the stain with wet/dry sandpaper, to reduce or remove the stain.

  9. We have a new pool so therefore a new well water fill.Ive adjusted the PH.Since it’s well water, it’s copper colored, but because the filter has been running all day, I can see the bottom…barely. I’m wondering if I should add the stain out now, or after I add the chlorine.I think the chlorine cleared it up last year, but not sure.I will add the chlorine towards dusk.Thanjs for your input!

    • Hi, best practice is to use the Stain Away (or other sequestering agent), before adding the chlorine, even during the fill is OK. High levels of chlorine from shocking can deactivate the metal control chemicals, or cause metals to drop out of solution, if not previously treated. If you have shocked the pool already, no problem, after the chlorine level drops add your initial treatment of Stain Away, and then add regular maintenance doses, every week or two, to keep minerals tied up in solution.

  10. We have a yellowish sticky stain around the inflated top ring of our vinyl swimming pool. We do not leave the pool up during the cold months. This appeared last year after setting up the pool for the summer. Pollen? What would be a safe cleaner? We tried hot water and lots of Dawn dish soap. Did not work.

  11. looks like a brownish/yellow stain. all in the deep end where debris lays over the winter. first 3 years running chlorine high for three weeks would get rid of them. not any more. brushing, shock, high chlorine levels do nothing. now stains are popping up all around where they never used to be and it’s june in pennsylvania.

    put an acid test bag of Stain Treat (oxalic acid ) and it removed the stain completely (along with some of the plaster color)but who cares, white is better than brown,

    so i bought two containers of this stuff to sprinkle all over the stained areas and it didn’t do much. seems like the the stuff works (a sequestrant & chelator ) but has to be very concentrated. i guess i have to buy around 30 little bags of the test bag stuff and put directly on the stain overnight…. the little bags cost $8.00 but that’s better than emptying the pool to acid wash.

    why are all these little brown stains appearing everywhere over the last two weeks for the first time ever?

    chlorine is pretty high and ph is a little low.

    please advise.

    • I’m not sure what the stain may be from, but it’s usually animal, vegetable or mineral. Most organic stains from leaves, worms, bird droppings, tree debris or berries will remove easily from concrete pools with high chlorine. Mineral scale however, takes an acid to dissolve it. Your stains may be a form of calcium or magnesium scale, mixed with dirt, algae, or leaf tannins. Check your pH level often, especially if your calcium hardness levels are higher than 200 ppm.

  12. Hello. We bought a foreclosure that had a mostly drained pool with leaves on the bottom covering a very BLACK stain . The pool then sat for 4 months collecting rain water and other debri . There was even a bicycle chain laying on the bottom. Countless bugs,Centipedes, glass, organic material , etc. we drained and acid washed it. Some stains came out but the chlorine bath was the best. It removed most of the stains on the entire pool except where the black stained were and the water and leaves from before we bought the house. The black stains are now brown dingy stains. We have repeated this process with 20 gallons of chlorine . Spraying a gallon a day. I think it’s done working now. We are still left with the stain. We don’t know what else may help. Also when we sprayed chlorine it would dry and create a reddish pinkish powder that we could wash away. When we soaked the stain with 10 gallons of chlorine for three days… before we decided spraying and letting in dry was better… the chlorine that was soaking turned bright pink. Don’t know what to do. Need to fill it soon . Advise would be GREATLY appreciated ! Thank you ! I will send pics .

    • Hi Kristen, you may never remove all of the stains, I think you’ve made a good effort thus far. They will lighten once you fill the pool and shock it, but they probably won’t completely fade away. Go ahead and fill the pool, balance the pH, Alkalinity, Calcium Hardness levels to normal pool ranges, and then shock the pool with a heavy dose of pool shock, sprinkling over the stained area. Brush and vacuum pool. After chlorine comes down, recheck the chemistry and add a Sequestering agent, aka “stain & scale” chemical like Scale Free or Stain Away to lock up iron or other metals and minerals, in solution. Add a maintenance dosage of metal control each week, because it breaks down in 1-2 weeks, or after shocking.

      • Try vitamin C tablets (ascorbic acid) over the suspected rust stained areas. Tie a few tablets together in a thin piece of fabric and let it sit over the stain for like 15 minutes – filter off. If this lightens or removes the stain, then it is rust.

  13. I have stains caused from shock sitting in place for a long time. My cleaner did not turn on for a couple of day after I added shock. The shock ended up on the bottom of the floor of our gunite in-ground pool and left white blotches. How do I get rid of them?

    • Hi, I guess what you have are ‘opposite-stains’, or where the area where the shock laid, is now bleached a whiter color. Not much you can do about that, except for perhaps a repeat treatment over the entire pool, or a drain and clean (acid wash) of the surface. But if you do check that water balance is correct, and some heavy pool brushing – may have some small effect.

  14. I have black and whiter stains on my plaster from someone throwing chlorine tabs on to the bottom of my white plaster, what can be done to get my plaster back to normal, looks like hockey pucks all over the place, and one 3ft by 3ft spot where it looks like it was sliding around.

    • Hi, well those stains are pretty difficult, as you probably already know. I would start by keeping very good balanced water, and then you can buy a device called a Jandy Stainmaster, to do localized acid washing, with a gallon of muriatic acid, bought locally at the hardware store. That won’t remove it completely (well, it might), but it’s the next best thing, short of draining and acid washing. You could also try some other methods, such as filling a tube sock with granular pH decreaser and placing it over the stain, moving it after 20 minutes or so with a pool brush, it will have less of an effect than putting acid directly on the stain. Unfortunately this is a type of stain that may be difficult to remove completely.

  15. Hi just bought a house with a pool. The bottom is full of black and dark gray patches. I used no phos but it’s still the same. I think is a metal stain all over.
    What can you suggest

    • Hi Alicia, I would recommend draining the pool and acid washing the surface, and refilling with fresh water, balanced to good levels. If the pool surface is that bad, I would bet the water quality is also poor, and it would be easier for you, to start out with fresh water. Plus, serious staining pretty much requires draining and cleaning. Unless this is a vinyl or fiberglass pool you have – then acid washing is not an option…

  16. Hi, I recently drained out my pool as there was alot of sand at the bottom. The walls are stained a bit. If I acid wash the pool, I was told that it would be rough, if I have to paint the pool with a few layers would it then become smoother? I might use an epoxy paint.

    • hi there – acid washing can make a surface rough, but it doesn’t have to… if you use a weak solution 1 part acid, added to 2 parts water, applied to moist surface, and rinse quickly after pouring over the surface from a watering can, the erosive effect is very minimal. But if you use straight acid, and let it burn for a minute or two, it will continue to erode, until it is diluted and rinsed. Acid washing is a purposeful stripping of a very thin (1 mm) layer of plaster, to expose fresh, unstained plaster beneath. It doesn’t necessarily make the surface rough, if you do it right. This includes the strength, the burn time, and controlling the acid/water run-off, by diluting and spreading it, to prevent acid/water wear paths on the floor, or at the end of steps, where the acid/water is rinsed off. Rinse randomly and profusely – and keep all surfaces wet. Start with a weak acid/water mix, in a flower watering can, for the first gallon. You can increase the strength if needed.

      Rough patches in plaster can be sanded with a rotary grinder or sanding blocks. Pool paint will also make a rough pool surface much smoother, and epoxy pool paint is the best type of paint to use in most cases.

  17. I had a bunch of pool stains from little seeds from my Royal and Queen palms and i brushed and brushed and they didn’t go away. Then I tried putting a chlorine tablet on the stain and waited about 10 minutes and voila absolutely removed!!! It acted like an eraser. I moved it to the next spot and it removed the stain. I did it for about 20 spots in my pool and they all disappeared. It was so simple I hope it helps someone else too.

    • Hi, yes it can, every few years it’s not a problem, if done gently! Acid washing is a purposeful stripping of the top 1/16″ of the plaster, exposing fresh plaster underneath. Aggressive acid washing can damage plaster and frequent acid washing will wear it thin. Plaster can be only 3/8″ thick in some spots, although it can be much thicker in other areas. So if you acid washed it every year, even gently, after about 10 years, the plaster would be worn away in thin spots exposing the plaster beneath. However, if you acid wash (gently) every 5 years, and replaster every 20 years, you should have no problem.

  18. My pool was resurfaced 15 years ago and acid was about 8 years ago. A few years later copper got into the pool and the side have black stains in places. My pool guy said that the pool couldn’t be acid washed again so it has been left. Is my only option to have the pool resurfaced again
    Thanks

    • Hate to disagree with your pool guy, but copper stains can be removed from plaster. In cases where copper stains are very heavy, it can be difficult to remove all staining completely, but in most cases, an acid wash will remove all copper staining. A third option is to embrace the stain, and learn to love the abstract beauty! If you want, add more copper, silver, iron, and use the pool as your art palette! 😉 I’m joking, but to some people, the usual blue/green copper stain is not too objectionable. Black copper stains aren’t as pretty however.

  19. Will acid washing a pool restore its color? My pool used to be a beautiful blue, now the color has faded. If not, what are the best options to bring the pool back to life?
    Thanks,
    Penny

    • Hi Penny, an acid wash is the solution to restoring colored pool plaster’s deeper colors. What happens is that a layer of calcium scale and other white-ish deposits onto all plaster pools. On white pools, you just don’t notice it. But on a colored pool the mineral layer can look undesirable in some cases. Acid washing with a mild solution 3:1 should remove a mild deposit. Heavier deposits may need a stronger mix or a secondary acid wash, to remove all of the deposits. It must be done carefully and gently, to avoid too much corrosion of the plaster. Ideally, you want it just strong enough and to sit just long enough, to eat through the scale, but not too much of the plaster beneath. After acid washing, refill the pool using a pre-filter on the hose, balance the water carefully, and try to keep it that way, while also using a stain & scale product like Stain Away to keep mineral scale from forming. If you are wondering if pressure washing is an option to an acid wash, it is, but it won’t work as well, and will take 3x as long.

  20. Hi, I would like to ask if you have come across black spots on the surface of the pool lining. The lining is Quartzon and only 4 months old and the pool is mineral. The black spots don’t have a head as I have tried to scratch them off. The water balance is normal and I have kept the water slightly acidic in hope the spots will go away. Thoughts?

    • Hi Tim, black stains that are not calcium crystals or black algae, could be mineral staining. If your pool uses a power ionizer, staining can result from overuse – copper and/or silver staining. Cobalt or manganese in the fill water can also produce dark spots, or it could be rust, from accidental metal shavings or pieces getting into the pool. It could also be stains from berries or tree nuts or animal waste – these will remove easily with chlorine shock sprinkled over the stain. If that doesn’t work, you can try sprinkling Stain Free or use a stronger acid like Stain Away over the spots. If that doesn’t work, draining and acid washing the Quartzon (a type of pool plaster, for those that don’t know) to remove the stains.

    • Hi, must be frustrating. Black spots you say? Could be Black Algae, lets just throw that one out there right away. If you inspect it closely (underwater with a mask), you will be able to tell if it’s algae, even if it won’t brush off easily, it will scrape off. Now it could also be metal staining, minerals such as manganese, or copper can make streaky black stains, maybe dots and spots, too. Thirdly, you could have stains from berries or acorns, or something – these would lift immediately with granular chlorine sprinkled over top, and a light brush. If shock doesn’t do anything, you can try crushed up Vitamin C tablets, and if that works, you could use Stain Free Ascorbic Acid stain remover. If neither of those works, you could use one of our Stain Away chemicals. But first, make sure that it’s not algae, and be sure the water balance is perfect, and that you are filtering and sanitizing and cleaning properly. Hope that helps, Good Luck!

    • Hi Ryan, using enzymes regularly can help control oily deposits and prevent waterline staining. Most waterline deposits are a mixture of dust, calcium, oils, etc. When calcium is very high in hard water, a white-ish scale can form at the waterline. Black or Grey-ish, you say? Try to see where it is coming from, (mulch, pollen, dust, auto/plane exhaust, oils, grease, soil).

      If you have TILE, you can lower the water level a bit, and scrub it clean with small amounts of abrasive cleanser, like Comet or Bon Ami. Use a textured sponge and apply pressure. This is easiest done inside the pool, in most cases. If there is scale deposited on the tile, you can add a cup of muriatic acid to a spray bottle that already has 2 cups of water inside. Wear goggles and gloves and spray over wet calcium scale, then scrub it with a brush, or scrape it with a putty knife, then splash off the acid with pool water. You can adjust the strength of the acid as needed.

      If you have VINYL, you can lower the water, but you don’t want to use anything as strong as acid or chlorine. Natural Chemistry makes a good enzyme based pool cleaner called Clean & Perfect, or use a pool tile and vinyl cleaner like, we have two – regular and ‘super’, which is more concentrated. These are mild enough to not harm vinyl liners, but strong enough to remove most waterline deposits.

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