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Why Swimming Pools Turn Green, Brown, or Black After Adding Chlorine Shock

Learn why your pool is that unpleasant color and how to fix it.

Learn why your pool is that unpleasant color and how to fix it.

Why Is My Pool Green?

There are a couple of reasons why swimming pool parts and water might change into different colors, including green, brown, black, purple, and yellow. One of the major reasons that all pool owners know is algae breakout and another that very few know is metal staining.

1. Algae Breakout

Algae is always caused by low free chlorine levels and it appears in green, black, or yellow in color on pool walls, on pool floors, in the water, and sometimes on pool equipment, depending on which algae you are dealing with.

However, if the pool water and parts discolor specifically when you add chlorine or shock it, and the chlorine level is just okay, you are not having an algae problem. It could instead be because of heavy metal presence in your water that is causing metal stains.

Algae Test

You can carry out an Overnight Chlorine Loss Test (OCLT). To do the test, add a normal amount of chlorine to your water and take the reading. This should be done in the evening/night when there is no sunlight that consumes free chlorine.

Take the chlorine reading the following morning. If little chlorine is used up (0–1 ppm), the OCLT result indicates it is not algae or any organism that could have used up a lot of chlorine (above 1 ppm). Thus, it's can only be metal staining as a result of oxidization by chlorine.

2. Heavy Metals

When heavy metals including copper, iron, silver, manganese, and magnesium are oxidized by chlorine inside your swimming pool, pool parts and water will turn to different metal stain colors and some of the colors are similar to those of pool algae (green and black), especially when just starting to grow. This may confuse inexperienced pool owners trying to figure out between algae breakout and metal staining.

Copper is always the most common metal you will find in your swimming pool water. This is because it occurs naturally in well and some municipal water and also finds its way into the swimming pool water through some chemicals we use, such as some algaecides.

Copper turns to a light green color when oxidized by chlorine inside your pool. Other metals you may find in your pool—especially when using well water—are silver that turns to black, iron that turns brown/rust, and manganese and magnesium that turn to purple when chlorine is added to pool water with compounds of these heavy metals.

Heavy Metal Test

To be sure if you are dealing with pool algae or metal stains in your pool, there are two options you can use. The easiest way is to test your pool fill-water for these metals using a test strip that supports heavy metal tests like the LaMotte ColorQ Pro 11 test kit, which takes readings of all pool chemicals and common heavy metals you can find in your swimming pool, including copper, iron, biguanide, and biguanide shock.

This article will explain why a pool turns green when chlorine is added and what you can do about it.

This article will explain why a pool turns green when chlorine is added and what you can do about it.

Causes of Heavy Metals in a Swimming Pool

Depending on which fill-water you are using in your pool, a couple of heavy metals may find their way into your pool. The most common metals in swimming pools are copper and iron. Other metals like silver, manganese, and magnesium may only get into your pool if you are located around areas where these metals are mined and you are using well water to supply your pool.

Copper in particular is the most problematic metal in a swimming pool, and it will turn to light green when chlorine is added. When any heavy metal is oxidized by chlorine, your swimming pool water, and parts will discolor as a result of metal stain. As a pool owner, you have to know how metals get into your pool and how you can control or clear them.

Here are the sources of most common metals like copper and iron, which have higher chances of getting into your swimming pool.

1. Adding Pool Chemicals With Heavy Metal Components

Using pool products with heavy metals as one of the major components is one of the ways you can get them into your pool. For example, constant use of some algaecides with excess copper will accumulate a significant amount of copper solution in a swimming pool over time. This may lead to pool water turning green when copper solution reacts with chlorine shock.

As such, it's always advisable to know your swimming pool's chemical components in detail and avoid chemicals that will cause additional problems in your pool.

2. Using Fill Water From a Well

Wells are commonly known to be one of the greatest sources of metals in a swimming pool, especially copper and iron. Iron reacts with chlorine to form iron III chloride, which is reddish in color. This is why your pool may turn to brown or rusty color when chlorine is added.

3. Using Metal Pipes and Pool Parts

During the construction of a swimming pool, copper, iron, silver, or any metal may be used in pipes and heaters. For instance, the use of copper parts requires a lot of pool care. This is because when the pH gets too low, metal parts (especially copper) will corrode into the water, forming a copper solution. Copper then comes out of the solution when oxidized by chlorine, causing a green color in your pool water and parts.

What Can You Do About It?

If you can't avoid using fill water from the well, using pool chemicals made of copper as one of the components, or using copper parts in your pool, you must be ready to deal with metals to avoid messing up your pool water.

Dealing with metals means frequent testing for metals and performing necessary treatment for every metal, mainly copper and iron.

I have been using Lamotte ColorQ Pro 11 to carry out different tests for metals such as copper and iron. This digital test kit is accurate and time-saving, since you can test all pool chemicals and common metals in your pool water in just one kit.

A few tips and tricks will keep your pool open for business all year.

A few tips and tricks will keep your pool open for business all year.

Steps for Clearing Metal Stains in your Pool

To clear metal stains in your swimming pool, simply follow these steps. I have included links to the products that I use.

  1. Get your free chlorine to 0.0 ppm by not adding more chlorine. This might take a few hours or days depending on the level of FC in your water.
  2. Add in the Swim's Polyquat 60 Algaecide after getting the chlorine to 0.0 ppm to prevent algae from growing in your pool during the process that might take a few days. Polyquat 60 or 60 Plus is the best algaecide for swimming pools, because it introduces no copper in your water and is also very effective in preventing algae.
  3. Get your pH to 7.2 using pH minus.
  4. Put your filter on circulation and add 1 pound of ascorbic acid for every 10,000 gallons of water in your pool to get stains away within 24 hours.
  5. Get the pH back using pH Plus. Then raise the TA using an alkalinity increaser, since ascorbic acid will reduce both.
  6. Add chlorine to raise your FC to around 3 to 4 ppm.
Don't we all just want our pool water to be beautifully clear?

Don't we all just want our pool water to be beautifully clear?

How to Remove Heavy Metals and Control Metal Staining in Your Pool

Treating heavy metals in your pool may be the only option for you when you have no other clean fill-water free of metals to use in the pool. There are a couple of ways you can take care of your pool so that heavy metals such as copper and iron will not affect your swimming pool when oxidized by chlorine.

Once you have an accurate test kit for metals and a few other chemicals we are about to discuss, your pool will never turn color due to different heavy metals.

1. Filter Well Water Before Entering the Pool

They say prevention is better than cure. Filtering your fill water from the well will be the best option if you want to have less work and more swimming. This is because water sourced from the well and some municipal water sources contain significant amounts of heavy metals, mainly copper and iron.

And in some cases, you may find some more heavy metals, such as zinc, magnesium, aluminum and silver in your pool water.

Each and every metal is oxidized and produces a solution of unique colour when chlorine is added to a pool with these metals:

  • Copper: Produces a light green solution or stain.
  • Iron: Produces brown/reddish/rusty coloured solution or stain.
  • Manganese and Magnesium: Produce purple solution or stain.
  • Silver: Forms a black colour stain or solution.

Whichever metal is causing problems in your pool, you can use a pre-filter to filter out these metals before they enter your swimming pool, where they will most likely be oxidized by other pool chemicals and stain your pool or change its water colour.

Moreover, when you prevent metals from your pool, you will save lots of money from buying pool chemicals that are needed to take care of metals once they are inside the pool.

Since I started my pool business, I have been using the Pleatco Disposable Pre-filter. I consider it the most effective pre-filter, because my clients who are using metal ridden fill-water have been sending me positive comments about saving on chemicals and time for maintaining their pools.

Pleatco's Pre-filter is also ideal since it can filter a one-time water capacity of 40,000 gallons and can easily thread onto any standard garden hose. This pre-filter can also be used for in-ground, above-ground and spas sourcing from metal-laden water.

2. Using Chemicals to Treat Heavy Metals in a Pool

The final option and the most tiresome method of dealing with metals in a swimming pool water are using chemicals. Besides being tiresome, these chemicals may be a little expensive and might need extra care to avoid more problems. That is why using them should not be an option if you can super-filter your pool water beforehand using a pre-filter.

Here are few chemicals you can use to treat your pool water to avoid staining pool parts and discoloring your water. The first chemical I will recommend is the one that absorbs metals from pool water and is placed at the skimmer basket or pump basket, and the second one suspends/holds heavy metals in a solution, and the last one removes fresh metal through the filter.

A. CuLator Ultra PowerPak 4.0

This is my second recommendation after a pre-filter since chemicals are not added directly into the swimming pool, but I use it on skimmers or pump baskets. CuLator Ultra PowerPak is capable of removing 4.0 ppm total dissolved metals from 20,000 gallons of pool water.

This product can be used for up to 30 days or longer, depending on the amount of metals in your water. It has an added advantage since you can use it to remove several metals, such as copper, iron, manganese, silver, cobalt and nickel, and can be used successfully on fresh or salty water.

B. Sequestering Agents

Metal sequestrants work differently by preventing metals from coming out of a solution inside a swimming pool. By preventing metals from separating in a solution, pool parts will not be discolored and water colour will not change.

When choosing a sequestering or chelating agent to use in your pool, you have to be careful. Most of the sequestrants in the market have a significant amount of phosphate as one of the major components, and you don't need a bunch of phosphates accumulating in your pool due to high chances of scaling inside and around the pool.

The only sequestering agent I know about without phosphate is one that I have been using for a while now: the SC-1000 by Orenda Technologies. Besides preventing metal stains and pool water discoloration, the SC-1000 is also capable of removing and preventing calcium scaling, since it controls calcium levels in pool water.

C. Metal and Metal Stain Remover

To remove fresh metals through the filter, you will need Metal Magic by Pro Team that also clears metal stains. Metal Magic is the best option compared to metal sequestrant since it practically removes fresh metals in your pool water via your filter.

This is also the best option I've found after the CuLator ultra power pack and is used on a monthly basis for preventive measures to avoid metal stains.

It's a great feeling to look out at a crystal-clear, healthy pool.

It's a great feeling to look out at a crystal-clear, healthy pool.

Additional Information

If you need more detailed information, check out my other articles:

Additionally, included below is a detailed video done by the River Bend pool company explaining how to use SC-1000 to control metals and scales in your pool.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

Question: We filled our pool with well water. Then my boyfriend added bleach to the pool. 30 minutes later the pool was brown. How do I fix this?

Answer: Brown stains in your pool means you have Iron metal component in your water that has been oxidized by chlorine.

To clear the brown stains in your pool, make sure your pH is not more than 7.2 and FC is low at 0ppm to avoid more brown staining, put your pool filter on circulation and add 1 pound ascorbic acid for every 10,000 gallons of water targeting most stains affected areas and the stains will disappear within 24 hours.

After clearing all the stains, before adding any chemical in your water, add initial dose of metal sequestrant like Orendas SC-1000 or metal removers like Proteam Metal Magic to prevent more metal stains. You will need regular treatment(weekly/monthly) of metal sequestrant or metal removers going onwards to control metal stains.

Alternatively, you can use CuLator Ultra PowerPak in your skimmer and/or pump bucket to remove metal compounds before entering your pool and prevent metal stains when you add chlorine.

Finally, measure and balance all your pool chemicals starting with FC and Cyanuric acid, pH and TA, and all other chemicals.

You can find all these mentioned products on Amazon through above links in the same article. If you more details on how to clear and prevent metal stains in your pool or spa, follow this link:

Question: I filled my small pool with well water and creek water. When I shocked it, it turned a light green. My pool store guy says there’s no turning back and I have to drain the pool and refill it and put an iron additive to the water. I can’t believe I can’t fix this without draining the pool. What if this was a 30,000-gallon inground pool?

Answer: You have Copper metal in your pool and that is Copper metal stain that is light green in colour. Reduce the pH to 7.2 and leave free chlorine(FC) to deplete by itself to 0ppm. You may have to drain your pool water partially to reduce FC to zero faster.

Add Polyquat 60 Algaecide by Pro Team that is metal free to avoid algae while FC is zero. Add ascorbic acid to your pool, 1 pound of ascorbic acid for every 10,000 gallons and metal stains should disappear. Add Metal Magic by Pro Team as directed for initial dose to remove all fresh metals in your pool water via the filter, use Metal Magic after every 1 month to remove fresh metals and avoid more metal staining in the future. Here is more on how to remove metal stains and prevent metal staining in the future:

Question: My pool turned a light green color but has no algae. I had a local pool center test my water and the free chlorine level was 3.84 ppm with a total of 5.32. PH 7.4. Alkalinity 110. Copper 0, phosphate 357, iron 0.2 ppm. I found 2 pennies at the bottom which were probably there for a couple of days. Could pennies be the source of my pool's discoloration? Our pool center recommended that I add 1 lb shimmer n shock which I did.

Answer: Since it's not algae and you have no Copper compounds in your water, the pennies could be the cause of discoloration. However, you need to have an accurate test kit that can measure metals because having it done by the pool store may not be reliable enough as some always give wrong readings. Light green color means there is copper in your water. You can use ascorbic acid to clear the stains before shocking your pool again if you see more green stains you will have to either add Metal magic by ProTeam to remove the metals through the filter or add metal sequestering agent to hold metal components and avoid metal stains when you shock your pool.

Question: I added my packet of hth to my small pool, but before I noticed and was already outing the packet, the hth was the dark yellowish-orange color. Now the pool is, so I tested it and the chlorine was low and I added 1lb of shock with running the filter pump. It’s still discolored. What should I do at this point to diagnose my pool's discoloration?

Answer: You could be having mustard algae that appear yellow in color and not metal stain.

Low chlorine encourages algae growth. As such, all you need is lots of chlorine. I prefer you to use liquid chlorine.

Raise free chlorine level to 12ppm and maintain it thereby adding chlorine when it drops to 8ppm at least twice a day until you get rid of algae, it could take a couple of days to get rid of algae.


Barack James (author) from Green City in the Sun on July 01, 2020:

Green pool water might mean you have Copper metal in your water that is oxidized by chlorine. You ascorbic acid to clear the green metal stain. Cloudy water also means your chlorine is too low and you need to fix it by adding more chlorine in your water.

LeeAnn Jillson on July 01, 2020:

My swimming pool is 18x36 inground. I have a new sand filter and sand. The chemical levels are all WNL and it has been vacuumed by robotic vacuum. The water is green and has become greener since vacuuming. Will phos free be any help? It is also very cloudy almost milky

Barack James (author) from Green City in the Sun on June 26, 2020:

First time adding the metal magic is actually an initial dose, subsequent monthly additions will now be maintenance dose.

Readyforsun on June 26, 2020:

When I add the metal magic should I do the initial treatment dosage or the rountine maintenance dosage since all the stains have already been removed?

Barack James (author) from Green City in the Sun on June 25, 2020:

You can add chlorine mmediately after adding metal remover. Make sure your Cyanuric acid level is also within the range.

Readyforsun on June 25, 2020:

How long after I get stains out and add metal remover do I need to wait before starting to bring chlorine back up?

Barack James (author) from Green City in the Sun on June 22, 2020:

You have a small amounts of metals inside your pool and you need to fix that by removing the metal compounds inside your pool to avoid stains.

Start by adding ascorbic acid inside your pool to clear the stains that are visible, then before adding chlorine again, add metal magic by ProTeam inside the pool to remove metals through the pool filter and backwash and rinse your filter.

Make sure your Iron remove is working so that no more metal gets into your pool causing stains when you add chlorine or when pH rises abnormally. You can also use CuLator Ultra PowerPak metal remover in the skimmer or pump basket to help in removing metals in your water before entering your pool.

Readyforsun on June 22, 2020:

Hello ... I need some advice.. I have had my pool for 10 years and never had had iron in my pool.. we have a soft water system that Removes iron from our water.. anyway we added water to pool when our system was out of iron remover and that’s where our problem starts!! So I used citric acid and it did an amazing job at cleaning the stains from the pool! However once I started adding the chlorine back it looks like the pool has some staining again.. no where near as bad but enough to drive me crazy.. should I do the whole process over again? Any advice would be greatly appreciated!

Barack James (author) from Green City in the Sun on June 12, 2020:

Happy to hear that Mike, I suggest that you add chlorine during the day and measure free chlorine level after 4 to 6 hours and raise it back if it falls by more than 1ppm in order to stabilize free chlorine level. Good luck.

Mike R. on June 12, 2020:

Thanks, again, Barack!

Chlorine test today dropped down to 0.6 ppm from yesterday's 1.5 ppm. No changes on Ph or alkalinity. The water cleared up to "sparkling clear" overnight as yesterday's chlorine and shock dissipated.

Today, I did give the pool another dose of the SC-1000 and ascorbic acid and will add more chlorine later.

However, this was all still encouraging. At least today the chlorine hadn't dropped to zero, so some progress - a measurable amount of free chlorine after 24 hours. Whoo hoo!

Will get the CuLator product ordered and in the pump filter basket.


Barack James (author) from Green City in the Sun on June 11, 2020:

Hi Mike, good to hear the progress in free chlorine level. Continue adding more chlorine to raise FC level to 3ppm and the cloudiness will disappear. Meanwhile you will still need a metal sequester doses until you get the CuLator metal filter.

Mike R. on June 11, 2020:

Thanks for the quick reply, Barack!

Even with the negative metal tests, I did go ahead and add the SC-1000 and ascorbic acid yesterday.

Today I retested the Ph and alkalinity and both were good. The water was still crystal clear.

After the tests, I added a chlorine based shock (2-1/2 lb.s) and a starter dose of di-chlor (also approx. 2-1/2 lb.s).

Again, as soon as the chlorine hit the water it dissolved and turned green. However, today, the overall cloudiness that this created was only about half as opaque as the past dosages. At least today you could just still see the drain in the deep end. This was encouraging.

After allowing the water to circulate for about 45 minutes, I did test the chlorine levels (free and total). The water was still cloudy, but the free chlorine finally measured at around 1.5 ppm (same with total chlorine - ~1.5 ppm).

So, this was a great improvement. I think if there is still a measurable amount of chlorine in the water tomorrow, I will re-dose the pool with the SC-1000 and ascorbic acid.

If needed, I'll also add more chlorine to try to get it back up to ~1.5ppm. Hopefully the chlorine test tomorrow will still show an effective amount in the water, and I won't need to add any more for at least a few days.

If this works out, I think using the CuLater product will be next to see if I can actually remove whatever the metal that is in the water.

I'm still baffled by the negative metal tests (Cu and Fe), but I guess if the SC-1000 and ascorbic acid are working, then I won't argue with success.

Barack James (author) from Green City in the Sun on June 10, 2020:

Since you are using well water as your fillwater, seems to me like you have small amount of copper metal that turns your pool greenish when you add chlorine and you can reduce its level by either draining and refilling a portion of your pool water with fresh water or using metal remover inside your pool.

But since your metal test turned negative, this could as well be an algae, so you need to be very sure it's metal stains and not algae.

If sure it's metal stains ( metal stains clears up when you add ascorbic acid) and draining and refilling pool water is expensive, you can lower metal levels in your fill-water either by using metal filter like CuLator Ultra PowerPak in your skimmer or pump basket, or use metal remover like Proteam Metal Magic inside your pool in initial dosage and frequent weekly doses as directed to remove metals through your filter.

About persistent cloudy water, if your Cyanuric acid is low as well like your free chlorine, you have ammonia in your pool and you need a lot of liquid chlorine to get rid of ammonia. However, before starting treatment for ammonia, you need to fix metal levels in your pool since you will be using a lot chlorine that will cause more metal stains.

Mike R. on June 10, 2020:

I'm at my wit's end, and have no idea what my problem is.

This year (after about 30 years of use), I'm switching my pool from Baqacil to chlorine. For the last 3 seasons, we've had a lot of trouble with a white fungus growing in the water lines and getting clear water has been a struggle. Basic stats:

Inground, 26K gal., sand filter, well water (delivered through all plastic pipes). All pool pump water lines are plastic. Vinyl liner.

Before opening the pool, I cleaned my sand filter and added new filter sand.

To switch to chlorine, we did not add any more Baqacil products when we opened the pool. I added an algicide and shocked with a non-chlorine shock. I then allowed another week pump on and filtering with the cover off.

I've balanced the Ph and alkalinity. The Ph is at 7.6 - 7.8 and alkalinity is around 250 ppm. I'm not having any issues keeping these numbers.

Test strips show hardness on the low end of the "good range."

Right now my water is clear as glass. The 8' deep end looks like it's 8" and not 8 feet deep.

However, I cannot get any chlorine into the water. Over the last month, counting the chlorine shock, I've added about 20 lbs of di-chlor. As soon as either the shock or dry di-chlor are added, as they dissolve, the water immediately turns a cloudy, yellowish green and develops suspended particles. These particles will filter out and / or settle to the bottom and can be vacuumed out.

When back-washing the filter, the dirty water looks like lemonade colored milk. The water will clear up to a sparkling state.

Testing for chlorine after 24 hours gives me essentially 0.0 free chlorine and maybe 0.6 total chlorine. No matter how much chlorine or shock I add, the test results come out the same in a day or less. The immediate result is the chlorine turns a cloudy yellow-green as it's added, the entire pool gets so cloudy and murky you can't see the bottom, even in the shallow end. Run the pump and filter long enough, and... clear water again but with no chlorine, free or total.

The Ph and alkalinity remain essentially unchanged, hardness doesn't change, etc. Status quo before the chlorine was added.

I thought that when I read this article about metals in the water I had found my culprit. Ah ha! At last a solution!

Unfortunately, I got my test kit (LaMotte) today for copper and iron, and the results are essentially 0.0 for both. (BTW, the test strips are not expired.)

Out of desperation, I did add 2-1/2 qt. of SC-1000 and 2-1/2 lb. of ascorbic acid, and I'll try to add chlorine again tomorrow after allowing the pump to run for 24 hours. However, I don't have high hopes.

Can you offer up any suggestions?

Barack James (author) from Green City in the Sun on June 04, 2020:

Brown stain could mean your pool has Iron and has been oxidized by high chlorine levels leading to the brown stains.

Stop adding chlorine in your pool, you need Ascorbic acid treatment when the pump is on circulation settings to clear metal stains.

After clearing the stains, you need to add ProTeam metal Magic to remove any remaining metal compounds so that you don't get more stains when you add chlorine.

Brenda L Sanchez on June 04, 2020:

Hi i shock my pool for algae problem ... add the flouccant and now my pool is brown color. Haven't vaccum the pool, as the instruction said . but is this normal that it turn brown?

Barack James (author) from Green City in the Sun on May 27, 2020:

Rob, sorry for the late response, we had a small hitch with comments section but it's now resolved.

The green tint on your water could be as a result of Copper metal being oxidized by high chlorine levels.

Seems you have some Copper elements in your water maybe as a result of using Well water in your pool, using Copper based Algaecide or you have a Copper based heat exchanger.

To clear the green tint on your water, add ascorbic acid but remember to lower or wait until FC level is 0ppm for faster results.

To avoid more stains when free chlorine is high or pH is low, you need to lower Copper metal level in your pool by draining and refilling a portion of your pool water, alternatively, you can add metal remover like ProTeam Metal Magic to remove metals through the filter and backwash your filter.

Here's more on how to clear and metal stains:

Rob on May 22, 2020:


Thank you for your quick reply to my question from earlier today. To clarify a bit (no pun intended) - using a test strip this morning shows my chlorine level has junped way up after shocking last night so I assume it is not algae - I could be wrong.

The water is still very clear although there is a noticable green/teal tint to it today vs. yesterday (pre shocking).

I do not see any staining on the returns or ladder - just a green/teal tint to the water, more prominant in the deep end

Barack James (author) from Green City in the Sun on May 18, 2020:

Don, it seems the level of copper components in your water is too high and that is why you get green stains when you add chlorine or when pH is too low.

To avoid adding more metal stain sequestrants, you can reduce the level of copper in your pool by draining and refilling a half of your pool water, or even more than a half if you can.

Buying a new Copper heater is not the solution unless it is rusty or something. If you use copper heater in your pool, copper compounds will accumulate in your water over time, and you can only control green stain by draining and refilling your pool water, or using a metal sequestrant, or a metal remover.

Just remember to keep your free chlorine and pH within the recommended range, and keep your water balanced by measuring Copper metal level in your pool water at least once a month and drain and refill your pool water if the level is high.

If draining and refilling your pool water is too expensive, you can add a metal remover like Proteam Metal Magic in your water to remove Copper metal components through the filter, then backwash and rinse your filter.

Don on May 18, 2020:

I’m being told the copper heat exchanger on my heater may be going bad and keeps reintroducing copper into my pool , I have treated my pool with ascorbic acid and metal out 4 times as directed and each time it has cleared the pool up very nice , only to have the green tint return after we add chlorine. No one can tell me how to tell if it is the heater . Please help , a new heater is $2800 and I’ve spent $325 on chemicals and still have the issue . Thank you

Barack James (author) from Green City in the Sun on May 12, 2020:

Bright green colour means your water has Copper metal and has been oxidized by chlorine. You can use Proteam Metal Magic to remove Copper compounds via the filter to avoid more green stain.

If you plan to use the heated copper pipe, you will have to add a given amount of Proteam Metal Magic on a monthly basis to avoid more metal stains.

No, it's not safe to swim in a pool with metal stain.

Jessica Wright on May 12, 2020:

My husband and kids set an experiment up to heat the pool water via heated copper piping, the pool water is now bright grren. 2 things how do we get rid of that and secondly is it safe to swim in

Barack James (author) from Green City in the Sun on April 11, 2020:

Before adding chlorine, you need to be sure you are dealing with green algae and not copper metal stains. If your pool turned light green only after adding chlorine, you are dealing with metal stains and you need ascorbic acid treatment which you can access via above link in this article.

However, if you know it's green algae, you need to add lots of liquid chlorine to raise and maintain free chlorine level between 8-12ppm until you see no more algae; meaning you will have to test your FCL at least more than once a day and top it up to 12ppm if it goes below 8ppm until you clear all the agae.

Maynor on April 11, 2020:

My pool is green I put chlorine and algae iit and it still green Help

Justin Fairley on October 13, 2019:

thank you, I will try the metal magic.

Barack James (author) from Green City in the Sun on October 12, 2019:

Brown color stain formed when you add chlorine means you have iron metal components in your water. Metals are common when you use borehole water or untreated municipal water as your pool fillwater. You can use metal sequester or metal magic by pro team to remove metals through the filter.

Justin Fairley on October 12, 2019:

Hi have had a problem this summer with pool liner turning brown after adding chlorine. I added ascorbic acid and it removes it but still keeps returning when more chlorine is added. I did take a water sample to my local pool shop and they said there was no sign of metal in the water.

They did recommend I partially drain the pool. Any ideas?