Swimming pool chemicals can be frustrating at times, but the solution to high chlorine levels is usually an easy one. Indoor pools are more difficult to handle, but many options are available. If you want to reduce daily chlorine levels without risking contamination, find out about the ultraviolet system.
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Method 1 of 3: Basic Technique
Step 1. Understand "chlorine smell" and hot eyes
Many people think that chemical smells or spicy eyes are signs of chlorine. In fact, it usually occurs after the chlorine breaks down into other chemicals. The correct response is usually to "raise" the chlorine level by shock treatment. However, it is better to use a test kit to get an accurate chlorine reading, as described below.
Step 2. Use a pool test kit
If you don't have one, test for chlorine using a test kit from a swimming pool supply store. Make sure the test kit measures free available chlorine (FAC) and total chlorine.
- As a general rule, free available chlorine (FAC) should be between 1 and 3 ppm. Total chlorine should not be more than 0.2 ppm higher than FAC. Local health regulations may have different requirements.
- If your pool also uses ozone or UV disinfection, the FAC can be reduced as low as 0.5 ppm.
Step 3. Get rid of the chlorine source
If the chlorine level is only slightly high (about 4-5 ppm), usually no chemicals are needed. Just stop adding chlorine to the pool, and the problem will likely solve itself.
To stop adding chlorine, turn off the chlorinator, chlorine feeder, or saltwater chlorine generator; take chlorine tablets from the pool skimmer (collection of dirt from the pool); or get rid of the chlorine floater. If you are not sure which system the pool uses, ask the pool manager or owner
Step 4. Uncover the outdoor pool
Ultraviolet light from the sun immediately decomposes chlorine. A sunny afternoon can get rid of 90% of the chlorine in your pool, as long as you've removed all sources of chlorine.
Ultraviolet light is usually not a good substitute for this step. See the UV method below for more information
Step 5. Swim while the chlorine is still at a safe level
Swimming helps lower chlorine levels, but only try this if the chlorine levels are a little high (4 ppm). Experts disagree about how much chlorine is harmful to swimmers. Often, public swimming pools are closed at 10 ppm chlorine, while some pools use a 5 ppm limit to be extra safe.
- Do not swim if the pool test gives other unexpected results, such as an incorrect pH or alkalinity.
- Don't swim if you smell a strong "chlorine" smell (and the chlorine test gives a high result). In fact, this smell comes from irritating substances called chloramines.
- Chlorine has an effect on the lungs. Chlorine is more dangerous in poorly ventilated areas, and if the swimmer has breathing problems.
Step 6. Replace some of the pool water
This is an expensive and slow option, but water will dilute the chlorine. Drain and replace the water about to of the pool. After refilling, the pool may take a long time to return to normal chlorine levels and pH.
If you have a filter that has a backwash option, this is the fastest way to partially drain the pool
Step 7. Test regularly
Repeat the pool test once or twice a day, or every two hours if the pool is still being used. If the chlorine level doesn't drop within a few days, try one of the methods below.
See Tips below for guidance on other test results, such as pH or cyanuric acid. If your test results fall outside these guidelines and are not corrected immediately, you may need to hire a professional
Method 2 of 3: Adding Chemicals to Lower Chlorine Levels
Step 1. Purchase a chlorine neutralizer from a swimming pool supply store
Ask an employee for help if you're not sure which one to choose. Do not use chemicals from other sources. Chemicals sold in swimming pool supply stores have specific concentrations intended for swimming pools.
- Sodium thiosulfate is probably the most commonly used chlorine neutralizer, but care must be taken when handling.
- Hydrogen peroxide is often the least expensive option, and breaks down into harmless substances. However, hydrogen peroxide is much less effective if the pool pH is below 7.0.
Step 2. Close the pool
Never add chemicals to the pool while the swimmer is using it. If other people have access to the pool, post a clear warning sign.
Step 3. Follow safety precautions
Many swimming pool chemicals can cause injury if they come into contact with the lungs, eyes or skin. Please review this safety checklist before you proceed:
- Read product labels carefully for handling instructions. Follow all recommendations for safety equipment, and review emergency protocols.
- Store swimming pool chemicals in a well-ventilated storage area, away from sunlight, heat and moisture. Do not store acid and chlorine near each other. Do not store dry chemicals side by side or under liquids.
- Only open one chemical container at a time. Close the container and return it to its storage area before opening anything else.
Step 4. Calculate what you need
Always follow product instructions to determine how to add the chemical to the pool, and how much to use. Many chemicals are available in different forms and in different concentrations, so general guidelines cannot cover every option.
- In general, when adding sodium thiosulfate, add about 0.5 ounces (15mL) per 1,000 gallons (3,800 L) of water.
- If you are treating a public pool, take more accurate measurements. A total of 2.6 ounces (77 mL) of sodium thiosulfate will reduce chlorine levels by 1 ppm in 10,000 gallons (37,900 L) of water. A pool supply store clerk or calculators for calculating the drop in pool chlorine found on the internet will help you with this formula.
Step 5. Add neutralizer in small doses
Adding too much neutralizer can cause a big problem: chlorine levels can drop to zero, and unused neutralizer will remain in the pool destroying any added chlorine as well. Use or of what you calculated.
Step 6. Wait while testing frequently
Give the pool time to acclimate according to the instructions on the label. Test often and don't enter the pool until the parameters are back to normal. If your measurements are stable, but the chlorine level is still too high, add another small dose of the neutralizer.
If your circulatory system is slower than average, you may have to wait longer for the neutralizer to take effect
Step 7. Raise the pH if necessary
Usually, these chemicals lower the pH of the pool. Be prepared to raise the pH once the chlorine levels return to normal. The pH value should be between 7.2 and 7.8, and ideally as close to 7.5 as possible.
Method 3 of 3: Using Ultraviolet Lamp
Step 1. Understand UV disinfection
Ultraviolet (UV) lamps designed for swimming pools can neutralize most germs. Lights alone cannot keep the pool safe. However, the lamp will reduce the amount of freely available chlorine (FAC) as low as 1 ppm, or even lower under some Regional Laws. Lights can also break down some of the irritating or harmful substances that appear in pools containing chlorine. Finally, although not usually used for this purpose, some types of lamps decompose the high levels of chlorine present.
Local health regulations may have different requirements
Step 2. Try a Medium Pressure (MP) UV lamp
The "MP" UV lamp is a versatile option with the following benefits:
- This lamp is the only common lamp, which will decompose the large amount of chlorine present. Even then, you will need a dose 10-20 times higher than the recommended amount for disinfection. It will likely take a lot of lights.
- These lamps are the most effective at breaking down chloramine, the substance normally responsible for hot eyes, irritated skin, and a “chlorine” smell.
- This lamp disinfects quite well, but is not the best option.
Step 3. Consider a Low Pressure (LP) UV lamp
This type of lamp, which is often called a purifier, has excellent disinfection capabilities, although you will still need to use a (reduced) amount of chlorine. This UV lamp can be an attractive option for public swimming pools.
- These lamps also tend to be cheaper and more durable than MP lamps.
- Advertisements may claim these lights get rid of chloramine. This is partly true, but in practice lights may or may not reduce obvious signs, such as burning eyes.
Step 4. Evaluate the other types
There are several other types of UV lamps, although these are less common. Here's a little bit of information to help you figure out what each product does:
- "Ultraviolet" actually covers a wide range of light with different effects. Usually, ultraviolet light is divided into UV-A (315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm). You should be able to find either the type of light or the wavelength range (such as 245 nm) for either product.
- Only UV-C light helps to disinfect the pool.
- Only UV-A light (including UV light from the sun) decomposes large amounts of chlorine. Even then, this decomposition would require a strong amount of light.
- These three types of UV light help break down chloramines.
Step 5. Test the pool after lamp installation
It is recommended to hire a professional to install the UV system. Once the system is installed according to specifications, very little maintenance action is required. Continue testing the pool for chlorine levels as usual, keeping the chlorine level at 1 ppm or another low level as recommended by the product or local law.
Tips
- Chemicals for swimming pools degrade over time. For best results, don't buy more than you will use in a season.
- If you smell "chlorine," you are actually smelling a byproduct called chloramine. Usually, this is a sign that you need to add “more” chlorine to make the pool safer. Shock treatment is a common response in home swimming pools.
- If you need to quickly sanitize your pool, super-chlorinate it, then chemically lower the chlorine level.
Warning
- If you still get unexpected results, check the other test results. For a stable chlorine level, the pH should be between 7.2 and 7.8; alkalinity should be between 80 and 120 ppm (depending on the type of chlorine), and cyanuric acid should be between 30 and 50 ppm. Local health regulations may have slightly different standards.
- In some areas, pool testing includes a substance called orthotholidina, which has been linked to cancer risk. Wear gloves while handling this test, and do not throw the sample back into the pool. Note that these tests only measure total chlorine, not the "free" chlorine actually available for disinfection.
