Green water or floating algae are a common problem in swimming pools. Treatment may require the use of different chemicals and you need to wait a few days to see results, especially if the algae have had time to build up. However, you can avoid them, without too much effort, by ensuring regular pool maintenance.
Steps
Method 1 of 3: Killing Algae with Chlorine
Step 1. Use chlorine to kill algae
If the water has turned green or you notice visible clusters of algae, there is not enough chlorine. A shock treatment with a large amount of chlorine is the most effective way to kill existing algae and restore the pool to proper sanitation. Generally, this procedure allows you to restore a normal situation in 1-3 days, but if the conditions are really bad, it can take up to a week.
The other methods that will be described below are quicker, but do not solve the underlying health problem. They are also more expensive and can cause side effects
Step 2. Scrub the walls and floor of the pool
Brush vigorously to remove as much algae as possible. This will reduce the time it takes to kill them and prevent them from blooming. Be particularly careful in cleaning the passageways, behind the steps, but also in the other corners and crevices where the algae tend to adhere more easily.
Make sure the brush is suitable for the type of pool liner. The steel ones are effective on concrete, while the nylon ones are perfect for vinyl pools
Step 3. Check the safety of chemicals
You will need to handle dangerous chemicals at various stages of cleaning. Always read the warnings and safety information on the package before using the product. At a minimum, however, follow the following standard safety measures for pool chemicals:
- Wear gloves, goggles, and clothing to cover your skin. After using the product, wash your hands and check for traces of chemicals on your clothing.
- Don't inhale chemicals and be extra cautious when handling them on a particularly windy day.
- Make sure you always add the chemical to the water and never water to the chemical. Never put wet dispensers back into the product container.
- Store them in a safe place, in a fireproof container, out of the reach of children, on separate shelves but on the same shelf (not on top of each other). Many chemicals explode when they come into contact with other chemicals.
Step 4. Adjust the pH of the pool
Use a kit to measure this indicator. If the level exceeds the value of 7, 6 - which is quite normal if there is an algae bloom - add a substance to reduce the pH (such as sodium bisulfate), following the instructions indicated on the package. Make sure that the pH is around 7.2-7.6 to make the chlorine action more effective and reduce the growth of weeds. Wait at least a couple of hours, then test the water again.
- The kit that uses the tablets or the dropper is much more accurate than litmus papers.
- If the pH is back to normal but the total alkalinity is above 120ppm, read the pH reducer label to find a way to bring the pH back to between 80 and 120ppm.
Step 5. Choose a chlorine shock treatment product
The chlorine you use for routine maintenance may not be the best choice for a shock treatment. The ideal would be a liquid product, specific for swimming pools and should contain sodium hypochlorite, calcium hypochlorite or lithium hypochlorite.
- Avoid calcium hypochlorite if the water is quite hard.
- Any hypochlorite element is flammable and can explode. Lithium is quite safe, but much more expensive.
- Do not take chlorine products in tablets or granules (such as dichloro or trichlorine), as they contain stabilizers which should not be added in large quantities in swimming pools.
Step 6. Add an additional large dose of shock treatment product
Check the instructions on the product label to perform a "shock" treatment. Use three times the amount of product if the water is particularly cloudy, or even four times if you can't even see the top step of the ladder. Make sure the filter is running and add the shock product directly to the water along the entire perimeter of the pool (if the liner is vinyl, pour the chlorinated product into a bucket of pool water first, to avoid damaging the material color).
- Attention: liquid chlorine can explode and produce corrosive gas if it comes into contact with chlorine in tablets or granules. Never pour liquid chlorine or any other product that contains it into the pool skimmer.
- Since UV rays break down chlorine, the shock treatment is much more effective if it is performed in the afternoon, so that it works all night.
Step 7. Re-analyze the pool water the next day
When the filter has been running for 12-24 hours, it examines the water. Dead algae have a white or grayish color, hang on the surface of the water or settle to the bottom. Regardless of whether they are dead or not, take another test to check the new chlorine level and pH.
- If the chlorine level is higher (2-5 ppm), but algae are still present, keep it at this threshold for the next 2 days or so.
- If the chlorine level has risen but remains below 2 ppm, a second treatment is required the next evening.
- If there have been no significant changes in the chlorine level, it probably means that there is too much cyanuric acid in the water (more than 50 ppm), due to the fact that chlorine in granules or tablets has been used which can "block" the chlorine you are using, making it ineffective. The only way to combat this phenomenon is to perform repeated shock treatments (even several times) or partially empty the pool.
- Many leaves or other elements in the water can also "eat" the chlorine. If the pool has not been used for a long time, shock treatments will be required for a whole week.
Step 8. Scrub the pool with a brush and analyze the values every day
Brush the walls vigorously to eliminate new algae growth. Within the next two days, the chlorine should kill all the algae. Do the water test every day to check that the chlorine levels and pH are acceptable.
A well-maintained swimming pool should have approximately the following values: free chlorine at 2-4 ppm, pH between 7, 2 and 7, 6, alkalinity of 80-120 and water hardness of 200-400 ppm. If there are slight differences from the standard values this is not a problem, so if the pool has slightly different values, you don't have to worry
Step 9. Free the pool of dead algae
Once the water is no longer green, use a wet vacuum to get rid of the dead algae and leave it on until the water is completely clear again. You can skip this step and run the filter, but only if it is powerful and if you are willing to wait a few days for the cleaning to complete.
If you find it difficult to get rid of all the algae, add a coagulant, or flocculant, to bring all the algae together. These products are on sale at specialty stores, but for a home pool it may not be worth buying
Step 10. Clean the filter
If you have a diatomaceous earth (D. E.) filter, turn on the backwash. If, on the other hand, the filter is a cartridge, clean it with a high-pressure cleaner and then with diluted muriatic acid or liquid chlorine, if necessary. If you don't clean the filter thoroughly, dead algae could clog it.
Method 2 of 3: Other Treatments
Step 1. Improve water circulation if the presence of algae is limited to a few small areas
If there are only small clusters of algae that have not yet spread throughout the pool, it probably means that the water remains stagnant in those areas. Check that the water jets are working properly and that they are directed towards the center of the pool, forming an angle with the walls, so as to create a spiral turbulence.
Step 2. Collect the algae with a flocculant
The flocculant, or coagulant, lumps the algae into a single lump that you can easily collect with the wet vacuum cleaner. It may take a full day of hard work to get this job done, but in the end the pool will be perfectly clean. This is the fastest way to make your pool look good, but be aware that it does not guarantee the hygienic safety of the water for swimmers. If algae can multiply, so can viruses and bacteria; then, afterwards, you have to perform shock chlorination to sanitize the water and you will not be able to swim in the pool until the chlorine levels and pH return to standard values.
Step 3. Treat the pool with an algaecide
This product certainly kills algae, but it comes with some negative consequences and is quite expensive, so it may not be worth it. Here are some factors that you need to consider when deciding to follow this method:
- Some algaecides are not effective enough to eliminate existing bloom, especially if you have black algae. Ask the shop assistant to give you some advice or in any case choose a product that has at least more than 30% of active elements.
- Quaternary ammonium algaecides are cheap, but they foam in the water and many people find this somewhat annoying.
- Copper-based algaecides are very effective, but expensive; they also have a tendency to stain the walls of the pool.
- Once you have added the algaecide to the water, wait at least 24 hours before adding any more chemicals.
Method 3 of 3: Preventing Algae Formation
Step 1. Do good pool maintenance
If you maintain a correct chemical balance of the water, algae should never form. Regularly analyze the water to check the levels of free chlorine, pH, alkalinity and cyanuric acid. The sooner you identify the problem, the better you will be able to handle it.
Ideally, quality tests should be performed every day, especially in the week or two following the algae bloom. Try to always analyze the water at least twice a week during the summer season
Step 2. Add algaecide as a preventative method
When the pool is in normal condition, the ideal is to use small amounts every week. This way, you can kill the algae colonies before they have a chance to develop. Read the instructions on the package to know how to use.
Be sure to follow the instructions for regular prevention and not for an existing bloom, as excess product can cause stains on the walls, bottom and cause foaming
Step 3. Eliminate the phosphates
Algae feed on various elements dissolved in water, especially phosphates. The phosphate kit is an inexpensive tool for verifying its presence in water. If these elements are present, get a specific product, available in specialized shops for swimming pools, to eliminate them. Let the filter, automatic vacuum cleaner or manual vacuum remove the phosphates for the next two days. When they return to a standard level, you can go for a shock treatment.
Swimming pool experts disagree on acceptable phosphate levels. 300 ppm is probably quite low, unless you have recurring algae problems
Advice
- If you have time, add only half of the recommended amounts of chemicals and supplement the rest a few hours later if necessary. This reduces the risk of exceeding the indicated doses, which could make it even more difficult to bring the chemical values back to standard levels.
- Check the filtration system carefully throughout the procedure. Backwash or clean the filter meticulously whenever the pressure rises 10 psi above the normal level. Dead algae collected by the filter can get dirty quickly, so it needs to be cleaned constantly.
- The heat and the sun break down the chlorine and encourage rapid algae growth. Always check the level carefully during the hot summer season.
- For the winter season, get a mesh cover that prevents debris from entering the pool, but allows water to pass through.
