Metal Laden Swimming Pool Water: Fixing Metal Stains and Pool Discoloration
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Metal Stains: Fixing Swimming Pool Discoloration
Unfortunately, there is no any practical way of removing metal compounds from swimming pool water.
The only possible way to get rid of metals in the pool is to completely drain the pool water; and replace it with water with no metal components: That seems expensive!
As such, before actually building that pool; it is always very important to test the source of your pool water for metal or iron content, and avoid water source with iron in it.
Ideally, water sourced from wells always is iron laden and should be avoided at all cost. Maintaining swimming pool with metals in the water is relatively hard and kind of expensive.
Another form of metal that may be present in pool water is copper: However, copper may only find its way into the pool from chemicals used in the pool such as algaecides and ionizers, and from eroded pool parts with copper like heated exchange coil when pH gets lower than 7.0 ppm.
Pool water discoloration and metal stains problems are very common in pools with lots of metal component: Water discoloration may come in different colors.
Possible colors of metal stains may be black, green, rusty, brown, orange, and yellow; which may occur at different spots in the pool water such as; at the bottom of the pool, along vinyl liner, fiberglass pool surfaces, pool steps, and rust on various parts of pool equipments. However, the pool water should still remain clear if the cause is metal stains.
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In most cases, cloudy or murky pool water is not associated with metals. On the other hand, not all green or black pool water are caused by algae, but may occur as a result of metal stains formed when pH is raised or free chlorine is added into the pool water with iron or copper compounds in it.
To avoid future metal staining in your swimming pool, I recommend using sequestrants on a regular basis in your pool: More details about sequestrants are included in later sections in this post.
Testing pool Water: Metal Stains or Algae?
Before taking any action to treat discolored pool water; you need to be certain of the cause: It could be algae or metal stains.
If you suspect the stain is caused by iron or copper metal compounds in the pool water, try Vitamin C test.
Vitamin C test uses ascorbic acid to identify metal stains: Hold vitamin C tablet or any form of ascorbic acid against a potion of stain for about 30 seconds.
If the stain vanishes or lightens, then it is iron stain and not algae: Having identified the stains as metal stains; it is time to get rid of them.
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How to Get Rid of Metal Stains in 5 Easy Steps
Note: If you strictly follow every single instruction in this section; you will definitely have a clear and ready to use swimming pool in less than 24 hours. It doesn't work for some people simply because they ignore some important small details, and then blame useful products unnecessarily.
Step 1: Lower Chlorine Level to 0.0 ppm
To get rid of metal stains; you will need . But first things first; ensure that you take down chlorine to 0.0 ppm using a neutralizing chemical, direct sunlight, or diluting using fresh water. ascorbic acid
(Which pool water test kit do you use? I thought you would like to read about LaMotte ColorQ Pro 7 digital pool water test kit!)
Lowering chlorine to 0 is necessary as chlorine will immediately eat up ascorbic acid and it won’t work for you in removing metal stains in the pool.
Very important; you can use poyquat 60 as directed during this process to prevent algae from thriving in the water while your chlorine is at 0.
Step 2: Lower pH Level to 7.2 ppm
Lower your pH level to 7.2 ppm if it’s higher than that: This is necessary since high pH levels causes metal staining and that is what you need to take care of.
Step 3: Run Filter and Add Ascorbic Acid
Put your pools filter on circulation if it's not on: You need about one pound of ascorbic acid for every 10,000 gallons, so the amount to add will depend on the volume of your pool.
Using a tin or a cup, drop the ascorbic acid down the sides of the pool while going all round the perimeter of the pool.
Let the ascorbic acid circulate for around 30 minutes; and watch how the metal stains fade away before your eyes.
If you still see some small stains after 30 minutes, add more ascorbic acid on the spots you still see the stains while the filter is on. Leave the filter on 24/7.
After 24 hours, all the stains should have faded away. Start rebalancing your water chemistry after 24 hours.
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Step 4: Getting pH and Alkalinity Back to Normal Levels
Ascorbic is a strong acid and will definitely bring down pH and total alkalinity (TA) levels. You can use soda ash (washing soda) to bring up pH and TA at recommended levels slowly by slowly while testing since you don’t want pH or TA to get out of balance again.
Remember that pH for pool water with metal compounds should be maintained around 7.2 ppm to avoid further metal staining.
If your TA is within the recommended level but you still need to raise your pH, you can use borax to raise your pH to 7.2 ppm. Borax may have small effect on TA but not like soda ash.
Step 5: Getting Chlorine back to Normal Levels
After getting pH and TA at recommended level, it is time to raise your free chlorine level. You need to use liquid chlorine bleach for this purpose.
Be cautious while adding chlorine and watch for any metal staining in the process. Ensure that you keep your chlorine at the minimum level possible depending on the available Cyanuric acid level.
Avoid shocking your pool for about two weeks to allow ascorbic acid to be completely used up: After about two weeks, you will notice chlorine being used up in the pool like usual: You can then begin to shock your pool carefully watching not to add excess chlorine.
Important: High levels of pH and chlorine will definitely precipitate any metal compound that is not treated (Sequestered) out of the pool water to form metal stains again. So, how do you treat pool water with metal compounds to avoid staining?
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How to treat Metal laden Pool Water to avoid Metal Staining
Since it is impossible to remove metals from the pool water, the only possible solution is to prevent metal stains from forming in the swimming pool.
Ideally, using regular doses of sequestrants in pool water with metal compounds will prevent metal staining when pH or free chlorine is added into the water.
How does this happen? Sequestrants naturally bind to the metal, preventing them from depositing as stains in the pool water.
Sequestrants slowly break down in the water and you need to add it more regularly to maintain the correct levels in the pool water for it to be effective.
Finally; I just thought you should know: Using borates in metal laden pool water may be useful in avoiding metal stains since borate ensures:
- More stable pH by prevent pH drifting
- A reduced chlorine usage since they act as sanitizer
Goodluck and happy swimming!
Source of Information: All the information included in this post are based on knowledge from my profession as a chemical engineer, personal working experience of more than 7 years, and standard rule and regulations by relevant bodies.