The cool water in the pool saves you from the summer heat, but if the pool is dirty it is unpleasant to use it. Stains can appear from time to time on the walls of the pool, so it is important to notice and eliminate them in time. Sometimes this is easy, and sometimes just rubbing the surface is not enough. Stains on the walls and bottom of the pool can be caused by metal in the water and by organic matter that remains in the water. To understand what kind of stain you are dealing with, you first need to pay attention to its color.
Method 1 of 4: How to determine the type of stain
Step 1. Pay attention to the color of the stain to understand what is causing it
The spots can be of different colors. The color will help you determine the cause of the stain. Different types of stains are removed in different ways.
- Most often, stains are caused by metals and organic matter and can vary in color.
- The spots can be greenish-brown, reddish-blue, blue-green-black, greenish-brown-red, pink-red, and brown-black-burgundy. Try to determine the color of your spots.
Step 2. Search the pool for organic stains
They come from leaves, berries, algae, worms, dead animals and organic debris that ends up in the pool. If the debris is not removed immediately, it will settle to the bottom and start to rot. Fortunately, removing organic stains is fairly easy.
- Organic stains are usually green, brown, blue-burgundy. If there is organic debris (such as leaves) at the bottom of the pool, the stains are more likely to be organic.
- If you suspect that the stain is organic, try applying some chlorine to the stain. If you rub the stain with a soft brush or sponge, it will come off. If the stain is caused by metal, it will remain on the surface.
Step 3. Look for inorganic stains, that is, stains caused by metal
Metal connections can enter a pool of water from a well or due to pipe corrosion. A small piece of copper (such as a copper coin) is sufficient to form the stain and will begin to oxidize. Rust, manganese, iron and copper can enter the pool. If you notice rust-colored stains under the stairs, it is most likely metal. The ladder should be inspected for rust. Examine the areas near the stairs, around the drain, and under the threshold. If the spots are reddish, brown, or very dark, most often it means they are caused by metal.
- The stains are usually due to iron, manganese and copper. Copper gets into the water from ionizers and also from rust on copper and brass pipes. Such spots are blue, green, blue-green, black or maroon. Iron enters the pool from well water due to corrosion of iron pipes and fittings and causes rusty brown, gray or gray-brown stains. Manganese enters the pool of water from a well and forms patches of pink, dark brown-black and burgundy colors. Calcium is found in plaster, in cement mortar, in lime mortars and in pool products containing calcium hypochlorite. Calcium precipitates out as white crystals.
- If you have a metal stain in front of you, it is important to establish what kind of metal formed it in order to know how to treat it.
- Often the cause of the formation of blue-green copper spots is a violation of the acid-base balance of water. Low pH and high chlorine levels can corrode the copper heater in the pool. It is important to monitor the condition of the water to avoid the formation of metal stains.
Step 4. Seek help from a professional pool cleaner
If you do not want to remove the stains yourself, contact a dedicated service. You will need to sample the water so that the technician can determine which metals are causing the staining. After that, you will be advised a special remedy.
Step 5. Collect the sample water in the correct manner
Prepare a clean jar or bottle, with the opening facing down towards the water. Submerge the container gently in the water and turn it over to draw in the water. Do not collect water near a drain or pool water outlet. It is best to take water from the middle of the pool. If this is not possible, try to select a location as close to the middle as possible so that the measurement results are as accurate as possible.
Step 6. Try to regularly measure the amount of all metals in the water
There are samples that only include bare metals. You should test the water for all metals.
Step 7. Use test strips to measure metal levels in water at home
Take a water sample from the middle of the pool. Quickly submerge one dry test strip in water. Without shaking off the water, hold it still in the air for about 15 seconds. The strip will begin to change color. Match the color of the strip to the flowers on the test strip jar. There are many types of strips to measure different substances, but you are only interested in the level of acid, alkali and free chlorine.
Use test strips at least once a week. Take a water sample to the laboratory once a month for a more accurate check, especially before the start of the season and at the end before the pool closes for the winter
Step 8. Try using a test kit with liquid chemicals
There are quality water test kits available, however acidity and chlorine test kits (with phenol red indicator and chlorine indicator) are sufficient for the home pool. These test kits will give accurate results, but you must be able to distinguish color shades. As you add chemicals to the water, they will change color. You will need to match the resulting color with the description on the package. Remember that it can be difficult to distinguish between shades.
- There are tests that allow you to investigate the concentration of chlorine in water. They appear as a yellow liquid that needs to be added to the water sample. The richer the color, the more chlorine in the water.
- Phenol Red is a substance that is added to water to check acidity levels. The redder the water, the higher the acidity value.
- When using tests with liquid chemicals, it can be difficult to know how pale or bright a color can be. Evaluate the color of the water against a white background.
Step 9. Find out if the problem lies in the water you fill the pool with
If the water comes from a well, test the water before it enters the pool. If the water contains a lot of metals, drain the pool by one quarter or half and add softer water. Leave the water in the system for 48 hours and check again. If there is still a high concentration of metals in it, repeat again.
If the water you are using is correct, it is likely that metal is entering the pool due to corrosion. Check the condition of all elements of the pool
Method 2 of 4: How to remove organic stains
Step 1. Remove organic matter from pool surfaces
Greenish brown spots are usually caused by organic matter trapped in the bottom (algae or leaves). First you need to remove these substances. Organic stains are easy to remove, but if they are not, they will fade in color over time and may be more difficult to clean. This process is quite slow, so it is very easy to overlook discoloration, especially at the beginning.
- If trees are growing above the pool, leaves, twigs or fruit may fall into the water. Use a net to remove these items from the water regularly.
- If the debris is already at the bottom, use a dedicated pool vacuum. A simple hand-held device or an automatic device with sensors will do.
Step 2. Treat the pool with acid
If the stains become stubborn, pump out the water and treat the pool with acid (assuming the pool has a plastered bottom and walls). This procedure cannot often be repeated as the acids will corrode the thin layer of the surface. To make the surface white again, treat it with acid once every five years.
Step 3. Treat stains with enzyme cleaner and scrub with a brush
This will quickly remove organic greenish brown stains. Try adding enzyme to the water. The enzymes will break down organic matter, and you may not even have to scrub the stains with a brush and use harsh chemicals that damage the pool surface. If the stains are located along the line of the water, because something is floating on the surface all the time, the enzyme treatment will destroy organic compounds and grease, accelerating the chemical reactions that break down the stains. Then scrub the walls with a brush to remove any remaining stains.
Step 4. Treat the pool with chlorine
Organic stains can be removed with strong water chlorination followed by brushing. Use a long-handled brush to reach all areas. Put a small amount of chlorine product in the water above the stain and it will start to come off immediately. Chlorine treatment is only suitable for pools with plastered bottom and walls. Do not use this product if you have vinyl flooring as chlorine can corrode the surface.
Check the acid-base balance of the water. Acidity should be in the range of 7, 4-7, 6 units, and alkalinity - 100-150 milligrams per liter of water
Step 5. Remove single stains with hydrochloric acid and a brush
Gently pour a small amount of acid onto a piece of PVC pipe, then pour the acid over the stain. Be aware that if the entire surface of the pool is covered with a thin layer of dirt, a bright spot may form at the acid treatment site.
Finally, add chlorine to the water to prevent algae growth
Step 6. Wipe off chemicals from the surface with an abrasive brush
Use a tile joint brush to clean the cracks. There are two types of brushes: for concrete and vinyl pools. Please make sure you have the correct type of brush before purchasing. The brush can be slipped onto a long pole and used to remove stains in areas that are difficult for you to reach.
Method 3 of 4: How to remove metal stains
Step 1. Remove as much metal as possible from the water
You can buy a separator for metal inclusions and install it in the pump intake filter (it will last for a month). This is the first step in removing stains and cleaning the pool. Separators are available in different sizes and capacities. Ask a consultant which one is right for you.
Step 2. Turn off all devices associated with the pool
Turn off chlorinator, metal ionizer, generator, UV delivery systems, and ozone generators. This will prevent the water from coming into contact with heaters, chlorinators and other non-filtration systems while treating stains with chemicals.
Step 3. Reduce the amount of chlorine to 0-2 milligrams per liter
The lower the chlorine level, the less acid you will need to collect. You can wait for the chlorine level to drop (for example, due to rain or naturally), but if you need to act quickly, add sodium thiosulfate to the water according to the manufacturer's instructions.
Add algicide to the water. Follow the manufacturer's instructions (pay attention to the method of application and the amount of the substance). This will avoid the formation of algae with a reduced amount of chlorine in the water
Step 4. Remove stains with ascorbic acid
Minerals can be treated with chemicals, and if you know a stain is caused by metals, or if you have not been able to remove stains using the methods described above, try special products based on ascorbic acid. You can also use vitamin C tablets. Crumble the tablets and rub the stain with them. After a couple of minutes, check to see if the stain is fading. Remember that ascorbic acid works better on iron stains and citric acid works better on copper stains.
- To remove large stains, add ascorbic acid to the water. Spread it evenly over the surface of the water. Start with 500 grams of acid per 38,000 liters of pool water.
- Leave the water circulating in the pool for half an hour.
- Check for stains. If not, add more acid and let the water sit for another half hour. Repeat until the pool is clear.
Step 5. Restore the acid-base balance of the water
It is important to monitor the acid-base balance, as well as the hardness of the water. Use automatic chlorinators, chlorine generators, UV delivery systems and ozone generators. Install a new metal separator in the water separator or pump suction filter so that the level of metal in the water does not build up. Keep an eye on the condition of the pool throughout the season.
Method 4 of 4: Preventing Stains
Step 1. Maintain your pool regularly
Preventing stains is easier than removing them. Have a water sample analyzed regularly or check the composition of the water at home every week. If you are filling a pool with water from a well, check that water as it can have a lot of iron in it, which leaves traces.
- Treat the water with chlorine every week to prevent algae formation.
- Brush the bottom of the pool several times a week as a preventive measure.
Step 2. Don't let the stains come back
Check the water regularly for metal content, as if there is a lot of metal in the water, stains will constantly form. Remember that metals can be found in the water from the well or can enter the water due to rust on equipment or pipes. It is important to check your metal levels every week.
- Use metal binding compounds (chelators). They bind minerals in solution and prevent them from spreading through the water and forming stains. Only use compounds that do not contain phosphonic acids, as these break down into phosphates and can cause algae formation.
- Disposable absorbent bags can also remove metals. Put one bag in a water separator or pump intake filter and it will collect metals such as copper, iron, manganese, cobalt, silver and nickel.
Step 3. To prevent organic stains from appearing in the pool, clean the pool from organic debris in time
Use a landing net or vacuum cleaner. Collect leaves, twigs and berries that fall into the water. Buy a sturdy awning that you can use to cover the pool when not in use.
Dark spots can be caused by mudslides or mulch. If you cannot solve this problem, cover the bottom and sides with dark plaster so that the stains are not visible
- Check the acid-base balance of the water and measure the total amount of solids in the water once a month or every three months.
- Pool chemicals, solutions, and test kits are available at specialty stores and some household hypermarkets.
- If you plan to use a store bought stain remover, you will need to lower the chlorine level in the water (the chlorine content should not exceed milligrams per liter) so that the chlorine does not interact with the cleaning agent.
- Owners of pools with a plaster bottom should monitor the acid-base balance and the amount of solids in the water.
- After treating metal stains with ascorbic acid, use metal bonding compounds to help collect the metal.
- Install a metal separator in the water separator or pump suction filter to keep metal out of the pool.
- Ascorbic acid can remove stains. Try vitamin C chewable tablets. Place them in a sock, chop them thoroughly, and then sprinkle them onto the stain. Then you will need to rub it with a brush, but the acid itself will be able to dissolve a significant area of the stain.
What do you need
- Sodium thiosulfate
- Vitamin C tablets
- Vitamin C
- Industrial enzyme that prevents rust formation
- Separator for metal impurities