Chlorine-Free and Reduced-Chlorine Pools
Clear, sparkling pool water requires a sanitation system, monitoring, and upkeep.

Reducing chemical use has great appeal, but it is critical to keep the family swimming pool free from dangerous germs. There are chlorinated, reduced-chlorine, and chlorine-free sanitization systems. The treatment system a homeowner chooses will depend on personal views, the amount of use the pool receives, costs, and convenience.

Why Treat the Water
Treating the swimming pool is important for two reasons: To protect the pool and protect the people. Balanced pool water is not too acidic or too alkaline, which protects the pool against corrosion. Having the right level of calcium ion concentration prevents surface etching and calcium scale from forming.

People can get very sick from dirty pool water. It’s important to protect the health of the swimmers by controlling disease-causing germs and eliminating nuisances like algae. While some bacteria can cause vomiting, cramps, or severe diarrhea, the most common bacterial infections are ear aches and minor skin rashes that resemble flea or chigger bites. Periodic ear aches and minor red rashes that come and go should be a red flag to pool owners that their pool is being under-treated. While algae is an eyesore, it is not a health threat.

Treating Pools for Germs
Whatever system you choose, it’s vital to have a clean pool. Waterborne germs are common, according to Roy D. Vore, Ph.D, of DuPont Chemical Solutions Enterprise and a member of the Association of Pool and Spa Professionals (APSP). Many germs can cause serious or life-threatening illnesses like diarrhea, skin infections, outer ear and eye infections, respiratory and brain infections, and hepatitis A.

Chlorine, in its various chemical forms, has been sanitizing pools in the United States for years because it’s inexpensive and it works. Chlorine has its downside, too. Whenever chlorine is added to pool water and organic compounds are present, disinfection by-products will be formed. According to Dr. Vore, up to 90% of chlorine added to a pool is consumed in oxidizing organic waste. Another way to look at this is that as little as 10% of chlorine added to a pool is used to control germs and algae. Chlorine also fades swimsuits and can cause skin irritation, eye irritation, and breathing problems. There are several products on the market that offer alternatives to traditional chlorine treatment.

Bromine. Bromine is a member of the halogen family, which includes chlorine. As such, it can cause some of the same breathing and skin issues as chlorine. But, unlike chlorine, when bromine comes into contact with nitrogen and ammonia from sweat, waste, or urine, it forms compounds but continues to sanitize the pool. It is not as stable as chlorine, though. Bromine burns off rapidly in the sun, leaving the pool with little or no sanitizing agent to protect it.

PHMB. Pool owners may not be familiar with polyhexamethylene biguanide or PHMB, known in the U.S. under such brand names as Baquacil® and SoftSwim®. In general, PHMB is more stable than chlorine, less irritating to skin and eyes than chlorine, and won’t bleach bathing suits or pool liners. But many pool owners have had trouble with PHMB because of the cost, maintenance requirements, and inability to control water mold and algae.

Salt-Water Systems. These systems are also called salt-water chlorinators or ionizers. With a salt-water ionizer, the pool owner can have chlorine in the water without having to buy or handle chlorine. To achieve this, a special electrolytic cell installed in the pool uses salt to generate chlorine at moderately low concentrations. Pool owners just add salt to the pool to feed the system.


Follow these tips to help keep your pool clean and safe.

  • Reduce the organic matter—leaves and insects—so the cleaning agents aren’t wasted. Pool covers can help.
  • Maintain the minimum concentration of sanitizer at all times.
  • Test the sanitizer and pH at least every other day.
  • Keep alkalinity and calcium hardness at proper levels. Test and adjust at least once a month.
  • Read and follow test directions and use fresh testers.
  • Know what alkalinity level is best for your pool—it varies from gunnite and concrete pools to vinyl and fiberglass.
  • Keep those with stomach bugs, diarrhea, and diapers out of the pool.
  • Shower first and consider installing a fun shower to encourage kids to rinse.
  • Ventilate indoor pools to avoid any respiratory problems from sanitizing agents.
  • Limit entry to the pool with fencing or a safety cover.
  • Keep a phone handy for emergencies and post a resuscitation sign that gives detailed instructions for reviving adults, children and infants.


The only challenges are keeping enough salt on hand, selecting a unit that is adequately sized for the pool, and maintaining a circulation pump that may run longer. Salt-water pool owners must still test the water to be sure the system is working. Also, because a relatively low amount of chlorine is produced, owners may need to add granular chlorine or a non-chlorine oxidizer like potassium monopersulfate to rid the pool of organic waste.

Low-Chlorine Options One popular alternative to heavily chlorinated pools is to reduce the amount of chlorine and use supplemental treatments.

UV and ozone systems use equipment that is permanently installed in the pool. UV systems emit a wavelength—ultraviolet light—that kills microorganisms as they pass through the chamber. Ozone generators produce ozone that is fed into the water as it passes through the system. These systems claim to kill germs that chlorine can leave behind. They can be used in conjunction with low levels of chlorine or along with a salt-water system.

Silver and copper ionizers are another supplemental system. Silver is an effective disinfectant that can operate with lower chlorine concentrations. Copper is known as an algaecide. Be careful if the pool has a white plaster shell —copper can cause green or blue staining, while silver can cause graying of the shell.

You can also reduce the amount of chlorine used by adding an oxidizer, like potassium monopersulfate, to reduce organic matter in the pool. It can be added separately, weekly, or as needed.

Labels and Care
Check local regulations and requirements before you select your treatment system, says Dave Purkiss of NSF, an independent not-for-profit organization that certifies products and writes standards for food, water, and consumer goods. Many jurisdictions allow the use of UV systems, and ozone and ion generators used with residual levels of chlorine, bromine, or—in the case of UV—hydrogen peroxide.

Make sure the sanitization equipment is NSF certified to meet NSF/ANSI Standard 50, which covers residential pools. Follow the directions and warning labels on chemical feeders or generator equipment. Be careful when mixing different types of treatment equipment, as many chemicals are incompatible and may react, causing fire, explosion, or release of dangerous gases.

Look for the Environmental Protection Agency (EPA) registration number. Products that serve as sanitizers, disinfectants, or algaecides must be registered with the EPA under the Federal Insecticide, Rodenticide, and Fungicide Act. EPA-registered products should have the words "disinfectant" or "sanitizer" on their label, which is important because bacteria can multiply rapidly in pool water.

Credit: Renovate with Tommy Mac