Diving into a gorgeous pool filled with cool, clear water is a great way to escape the summer heat. However, the idea of swimming in a dirty tub could dampen the excitement and make all friends run away. The appearance of stains of various kinds is a problem that must be faced commonly if you have a swimming pool and it needs regular maintenance to be solved. In some cases, removing stains is quite simple, but in others it takes more than just a few brush strokes. The stains that can attack the coating or flooring of a swimming pool are mainly caused by residues of metal or organic material present in the water. The first clue to diagnose the type of stain to be treated is given by the color of the latter.
Steps
Part 1 of 4: Diagnosing the Stain Type
Step 1. Focus attention on the color of the stain to be removed in order to trace the cause
The stains that normally appear in swimming pools have different colors, a key aspect to identify the correct treatment to use. Depending on the cause that led to the formation of the spots, you will need to adopt a specific solution to eliminate them.
- The stains that can be found in a swimming pool can be divided into two main categories: those caused by metal residues and those caused by organic residues. Both are characterized by a wide variety of colors.
- The color combinations that can be encountered include: brown-green, red-blue, green-black-blue, green-brown-red or brown-black-purple. Try to identify the color scheme of the stain you want to remove.
Step 2. Check the bottom of the pool for organic residue stains
This category is generally caused by leaves, berries, algae, worms, dead insects or other organic debris which, if left to decompose at the bottom of the pool, can stain it. If all these residues are not removed promptly, they begin to sink to the bottom and decompose. Fortunately, this type of stain is very easy to remove.
- Normally, the spots generated by organic debris take on a green, brown or bluish-purplish color. Diagnosing the organic nature of a stain should be simple enough, as it is characterized by the presence of debris, such as leaves, sitting on the bottom of the pool.
- If a stain that you think is organic seems suspicious to you, try treating it directly with chlorine. Stains of this type can be dissolved very easily using a simple soft bristle brush. On the contrary, the stains caused by metal residues will not be affected in the least by this simple treatment.
Step 3. Look out for any stains caused by metallic or inorganic debris
These substances can be introduced into the pool inadvertently through topping up with water from underground aquifers or by corrosion of copper pipes. To create even serious stains, an amount of oxidized copper equal to that of a penny is sufficient. The set of metals that can be present in a swimming pool water include rust, manganese, iron and copper. If the pool wall behind the ladder has rust stains, it is very likely that the source of the problem is metal, so you should carefully examine the ladder for signs of corrosion. Scan the areas near the pool entry steps, around the drain nozzle, and under the rim for signs of stains. Coppery brown or very dark, the latter are normally produced by metallic residues dissolved in water.
- The metals that normally tend to stain the walls or bottom of the pool are iron, manganese and copper. Copper comes from the ionizer and corrosion of the brass and copper pipes of the filtering, recirculation and water treatment system. This type of metal generates spots of blue, green, black or dark purple. Iron comes from water drawn from wells or underground aquifers, from the corrosion of iron pipes or joints and causes rust, brown, gray or greenish-brown stains. Manganese comes from water drawn from wells or underground aquifers and causes patches of pink, dark brown, black, or purple. Calcium comes from the plaster, mortar or cement used to create the pool lining or from a shock chlorination (also called "shock chlorination") based on granular chlorine (calcium hypochlorite) and manifests itself in crystals of White color.
- If a metal residue stain has appeared in your pool, it is important to identify the exact nature of the metal that caused it so that you can choose the correct treatment.
- The most common cause of the appearance of groups of blue-green copper stains is the incorrect use of chemicals related to routine pool maintenance. A low pH level and a high concentration of chlorine are the causes of corrosion of the heat exchanger inside the pool heating system. Performing routine water maintenance to balance all values correctly makes it easier to stop the formation of this type of stain in the bud.
Step 4. Talk to a professional
If you prefer a professional technician to deal with the problem, use the Yellow Pages to find a company that specializes in managing problems related to pool maintenance. In all likelihood, you will need to provide a sample of the water taken from the pool so that it can perform all the necessary checks to accurately identify the metal residues, and the relative concentration, that are damaging the pool. A professional in the field will also be able to direct you to a product specifically created to remove stains generated by the metals dissolved in the water of the sample you provided.
Step 5. Make sure you take the water sample to be tested correctly
Use a clean cup or bottle with the opening facing the bottom of the pool. Completely immerse the container in the water, then rotate it upwards to obtain a suitable water sample for analysis. Do not take it near the recirculation system outlets or skimmers. It is best to take the water sample from a central point in the tank. If this is impossible to do, position yourself as close to the center of the pool as possible for reasonably accurate results.
Step 6. Make sure you run a comprehensive test for metal debris as part of your testing routine
Some tests only detect certain types of metal, but a comprehensive test detects the presence of any metal in the sample taken.
Step 7. Use test strips to directly test the quality of the pool water
Take a sample in the center of the tank, then quickly dip a reagent strip into the water. At this point, take out the strip and leave it exposed to the air for about 15 seconds without removing the excess water present. The strip will begin to react to the substances present in the pool by changing color; uses the measurement scale on the package to compare it with the color appearing on the reagent strip and to be able to interpret the results obtained. There are different types of reagent strips on the market designed to test different aspects related to the quality of a swimming pool, however you will have to focus on pH, alkalinity and free chlorine.
Do these types of checks at least once a week. Once a month, take a sample of the pool water to a specialist shop for accurate and professional results. Do this especially when you close the pool for the winter and reopen it for the summer
Step 8. Try using a control kit with liquid reagents
These are very advanced kits, so in the case of a private pool you may have to limit yourself to testing the pH and chlorine level using a Phenol Red and Orthotolidine (OTO) kit. Liquid reagents can give very accurate results, but you need to be just as accurate in interpreting their color. For example, when you add chemical reagents to the water sample, the water sample changes color, so to get a correct reading of the results you will need to find the exact color gradation using the measurement scale on the reagent package. This way you will know what kind of treatment to take. Be very careful at this juncture because identifying the shades of the various colors available can be very difficult.
- Orthotolidine is a chemical reagent used to test the level of free chlorine present in water. It is a yellow additive which must be added to the water sample to be checked. The more the color of the sample turns yellow, the greater the concentration of chlorine in the pool water.
- Phenol red is a chemical that is added to a small sample of pool water to measure its pH. The redder the color of the sample, the higher the pH value detected.
- When using liquid reagents, it is very difficult to distinguish the various shades of color. In order to evaluate as accurately as possible, it is therefore very important to evaluate the samples with the reagent by placing them on a white background.
Step 9. Determine if the problem is caused by the water you use to top up the pool
If you use water from an underground well to perform this activity, test its quality before proceeding. If you find that this source of natural water has a high level of metals, proceed by emptying the pool about half or 1/4, then fill it using softened water. At this point, keep the pool's recirculation system running for at least 48 hours, then run all tests again. If the concentration of dissolved solids remained high, repeat the procedure.
If the water you use to top up the pool is of acceptable quality, it means that the metals present have most likely been introduced by the corrosion of metal parts. Check all pool equipment for obvious signs of corrosion to make sure you are not contaminating the water while using them
Part 2 of 4: Treating Organic Stains
Step 1. Remove all residual organic material from the pool surfaces
Normally, greenish-brown spots are related to the presence of organic material, such as algae or leaves, which settle on the bottom of the tank. All these substances must be removed as part of the routine maintenance process of the pool. Normally, these types of stains are not difficult to clean, but over time the pool tub will begin to take on a slight shade of dull brown that you will no longer be able to remove. This dull brown hue forms very slowly over time, making it very difficult to notice until it is clearly visible.
- If the pool is overlooked by tree branches that surround it, check for any leaves, berries or wood residues in the pool that have accidentally fallen into the water. If necessary, remove them using a common pool net.
- Any organic residues deposited on the bottom of the pool must be removed using a special vacuum cleaner to clean the pool. You can use a manual vacuum cleaner or an automatic vacuum cleaner equipped with sensors.
Step 2. Clean the pool using a chemical acid
If you have noticed that permanent stains have developed, you can remove them by completely emptying the pool and washing the liner with an acid (only if the pool is lined with plaster). This treatment is part of an extraordinary maintenance process, which cannot be performed regularly, as it involves the removal of a very thin layer of the tub liner. In order to restore the whiteness of the surface of the tub, it is necessary to wash it using an acid chemical product every five years.
Step 3. Try a shock treatment to remove stains using an enzyme and scrub them using a stiff bristle brush
In this way you should be able to quickly eliminate the greenish-brown stains that are generated due to the organic residues present in the water. You could try using an enzyme-based pool treatment chemical. All natural enzymes are able to dissolve the organic material responsible for the formation of stains in the pool, allowing them to disappear on their own or with a simple brush stroke, without the need to use a chemical abrasive that would damage the coating of the pool. If the stains are concentrated along the edge of the pool, due to the presence of organic material suspended on the water, an enzyme-based cleaning product can be useful to dissolve the organic compounds and oils, speeding up normal chemical reactions. With this method, the spots will practically disappear on their own. To make sure you get rid of any organic residue, thoroughly clean the walls of the tank with an enzyme-based treatment brush.
Step 4. Perform a shock chlorination (or shock chlorination) of the pool
The best way to treat organic stains is to significantly raise the level of chlorine present in the water, and then clean the surfaces of the tank with a special brush. You can use a hard bristle brush with an extendable handle that allows you to reach any point of the pool by moving along the edge of the pool. To perform shock chlorination, try spreading a small amount of product directly on the stain to be treated to see it disappear instantly. Be aware that this treatment is only suitable for pools lined with waterproof tiles or plaster, so do not use it if your pool has a vinyl coating as it may remove the pattern.
Test the water quality to make sure the pH level is balanced and the alkalinity is correct. The pH should be between 7, 4 and 7, 6, while the alkalinity level should be in the range of 100-150 ppm (parts per million)
Step 5. Remove localized stains using muriatic acid and a brush
Using great caution, pour the acid into a section of PVC pipe, then use it to direct the chemical directly onto the area of the wall to be treated. If all the tub liner is slightly stained, be cautious about using muriatic acid; otherwise you may end up with a completely clean and shiny spot in the pool surrounded by areas with a darker color.
After using the cleaning product, it is important to perform a shock chlorination of the pool to restore a high enough chlorine level to prevent algae from developing
Step 6. Do not use harsh chemicals with an abrasive action
To clean the thin joints between one tile and another in the covering, you can try using a rough brush. There are two types of brushes for swimming pools: one reserved for those in concrete, the other for those in vinyl. Before purchasing, carefully check which model is right for you. Once you have purchased the correct brush, attach it to the extendable handle, then use it to clean stains located in hard-to-reach places.
Part 3 of 4: Treating Metallic Nature Stains
Step 1. Follow all procedures necessary to remove any metal residue from the pool
One of the options available to you is to purchase a specific product to be left to act for a few days in one of the baskets placed in the skimmers. This is the first step in trying to get rid of most of these stains. Furthermore, it will facilitate the cleaning process of the pool. There are several brands to choose from, each offering products with different concentrations; the best thing to do is therefore to seek the advice of a professional.
Step 2. Turn off all equipment in the vicinity of the tank
Include chlorinators, metal ionizers, power generators, UV water disinfection systems, and ozone generators. When cleaning the pool with very invasive chemical treatments, it is always better to avoid that the water comes into contact with the heating, chlorination or any other system that is not needed for simple filtering placed in the vicinity of the pool.
Step 3. Decrease the chlorine level in the pool to between 0 and 2 ppm (parts per million)
The lower the chlorine level in the water, the less ascorbic acid you need to use for cleaning. You can wait for the chlorine level to drop naturally thanks to the rains or with the simple passing of the days, but since time is a very important factor you can speed up the whole process by adding sodium thiosulfate to the water, following the instructions given. on the packaging from the manufacturer.
Pour an algaecide product into the pool. Also in this case, make sure to follow the instructions on the package, regarding how to use and how to calculate the amount of product based on the size of the pool. This will prevent algae from forming during the period when the chlorine level is very low
Step 4. Remove stains using ascorbic acid
Since mineral residues react better to chemical treatments, if you believe that the stains in the pool are caused by metals dissolved in the water or that the advice given in the previous methods, relating to the treatment of stains of organic origin, cannot be useful to you, try using an ascorbic acid-based chemical. It is an acid found in some citrus juices which, in high concentrations, can be very powerful. You can experiment with a very effective home remedy by crumbling vitamin C tablets that you will have to rub on the areas to be treated. After a few minutes, you can visually check if the stain is starting to lighten.
- If the stain is very large, treat it by adding ascorbic acid directly into the pool water: spreading it evenly over the entire surface of the pool. You can start by using 225g of ascorbic acid for every 37,850 liters of water.
- Set the pool filter to the "recirculation" function and activate the relevant pump. Wait half an hour so that the ascorbic acid has time to act.
- Check the pool to see if the stains have disappeared. If not, add more ascorbic acid and keep the pool filter system running on "recirculation" mode for another half hour. Repeat the process until the pool looks clean.
Step 5. When finished, restore the correct values for the chemical balance of the tank water
In this step it is very important to monitor the pH levels, alkalinity and hardness to bring them back to the correct values based on the size of the pool. To do this, you may need to restore normal operation of any automatic equipment, such as chlorinators, chlorine generators, UV systems, ozone generators or metal ionizers. Place a new tablet or dose of the metal sequestrator that you normally use in the basket inside the skimmer to keep the level of metal residues dissolved in the water as low as possible. This is useful to prevent the appearance of stains on the walls and bottom of the pool during the entire season.
Part 4 of 4: Preventing Any Type of Stain From Appearance
Step 1. Make routine pool maintenance happen regularly
Preventing stains is certainly easier than having to treat and eliminate them. Each week, perform a comprehensive water quality test with an experienced professional or by using a water quality kit. If you use a water source other than the municipal aqueduct to top up the pool, it is also better to check the quality of this source as the water carries large quantities of iron and minerals, which can cause the formation of unpleasant stains.
- To prevent algae from forming, do light shock chlorination once a week.
- As a preventative measure, brush the bottom of the pool several times a week.
Step 2. Stops the formation of new metallic stains
Regularly check the level of metals dissolved in the pool water, as these stains occur when the concentration of these elements is very high. Remember that metals are naturally present in nature and can enter the pool through the water used to top up or result from corrosion of the equipment in the pool or of the plumbing pipes. Monitoring the level of metals dissolved in the water on a weekly basis is therefore very important.
- It uses a chemical metal sequestering agent, also known as a chelating agent. These chemical compounds are able to harness metals with a very strong bond, preventing them from remaining suspended in the water, contributing to the appearance of unsightly stains.
- On the market there are also disposable products with pre-filtering action to be inserted in the skimmer basket. They are also able to absorb metals dissolved in water, such as copper, iron, manganese, cobalt, silver and nickel.
Step 3. Prevent organic stains from forming by regularly removing natural debris that settles on the bottom of the pool
To remove organic residues such as leaves, berries, small insects or twigs, you can clean the bottom manually with a special net or with a vacuum cleaner; alternatively you can choose to use a fully automated robot. Also, you should consider purchasing a quality winter cover system, which allows you to close the pool during the winter season.
Dark spots are produced by muddy residue or mulch. If you can't prevent these materials from ending up in the pool tub, try replacing the wall and bottom cladding with a dark one to mask them
Advice
- If you have chosen to purchase a dedicated stain removal product from your trusted supplier, before using it, you will need to lower the chlorine level in the water to below 1 ppm, so that the chlorine does not conflict with the active ingredient of the chosen chemical product.
- Check the pH and alkalinity level of the water on a weekly basis, instead it checks the level of STDs (Total Dissolved Solids or TDS) on a monthly or quarterly basis.
- Chemical solutions, pool treatment products and water quality control kits can be purchased at most home improvement and DIY stores and those that specialize in pool management.
- If you are the owner of a pool lined with waterproof plaster, you need to pay close attention to the pH, alkalinity and STD levels of the water to avoid damaging the inner lining of the pool.
- After treating the pool with ascorbic acid to remove metal residue stains, you should treat the water with a metal sequestering agent to balance the chemicals properly.
- Ascorbic acid is able to remove stains. Try using vitamin C tablets, you will have to crush them (for example by hitting them with an object after putting them in a plastic bag) and spread them directly on the areas to be treated. You will most likely need to brush a little, but in most cases the stains will disappear in no time.
