Chlorine is used in pools primarily to control algae, which feed on nitrates and phosphates. Chlorine is an oxidizer, meaning it destroys these compounds and keeps the water crystal clear. However, chlorine’s effectiveness depends on three main factors:
- Temperature – In very hot water, like spa pools at 100°F, chlorine loses efficiency, which is why bromine is often used in hot tubs.
- pH – High pH levels (around 8.0–8.2) reduce chlorine’s activity. Lowering pH “activates” chlorine so it can sanitize effectively.
- Water hardness – Hard water decreases chlorine efficiency, which becomes especially relevant in salt pools.
Chlorine Exclusive Pools
Chlorine has been the standard for decades, but the health effects of using high levels of it to sanitize large pools are causing many to seek alternatives. New systems offer improved sanitation with fewer health risks, as high chlorine levels and their byproducts can cause various issues:
- Respiratory issues: Inhaling chloramines can irritate the nose, throat, and lungs. Long-term or heavy exposure is linked to increased asthma and other respiratory problems, particularly in lifeguards and competitive swimmers.
- Skin and eye irritation: Chloramines can strip the skin and hair of their natural oils, causing dryness, rashes, and a worsening of conditions like eczema. They can also cause red, stinging eyes.
- Gastrointestinal illness: Ingesting chloramines can cause stomach pain, vomiting, or diarrhea.
- Potential long-term risks: Studies have explored links between chronic exposure to chlorine byproducts, such as trihalomethanes (THMs), and higher risks of bladder and other cancers, though the evidence is still being debated.
Salt Pools
In the 1980s, saltwater pool systems emerged as a popular alternative to traditional chlorine sanitation. Early adopters praised the gentler feel of the water on skin and eyes and the lack of strong chemical odor. However, as the technology improved, a different set of long-term challenges became apparent.
While offering a better option than pure chlorine systems, saltwater pools face issues with higher initial costs and corrosive effects on pool surfaces and equipment. Over time, these systems can lead to a gradual buildup of total dissolved solids (TDS), which can cause:
- Difficulty maintaining water balance, which can reduce chlorine effectiveness and lead to increased algae growth.
- Scaling on pool walls, heaters, and filtration systems.
- Murky water.
- Corrosion of metal parts and accelerated deterioration of plaster finishes.
- Skin and eye irritation for swimmers.
Think of a salt pool like making Kool-Aid: you keep adding sugar until the water can’t dissolve any more. After a few years, salt pools often reach 100% saturation of dissolved solids, which causes:
- Chlorine efficiency to drop to around 30%
- Increased need for acid to balance high pH
- Scaling and fallout, meaning draining or acid washing every 2–3 years
Salt pools also require high maintenance:
- 500–600 pounds of salt to start
- Salt cells last about 3 years and cost around $1,000 wholesale
- Heavy use of acid and chemicals to maintain water balance
While salt pools have been popular in South Florida, they are not the most efficient or purest system for long-term maintenance.
Ozone and Mineral Systems
Ozone is extremely powerful—over 100 times stronger than chlorine. It destroys nitrates, phosphates, grease, lotions, and oils, which no other pool treatment can remove. Running the filter longer with ozone reduces wear on cartridges and other equipment.
Mineral packs (like zinc and silver) target algae nutrients, allowing you to reduce chlorine use by 70–80%. Combined, ozone and minerals produce:
- Purified water, similar to bottled drinking water
- Minimal hardness and chemical use
- Lower long-term maintenance costs
Maintenance for ozone/mineral systems is simple:
- Replace the mineral pack once a year
- Ozone generator lasts years without intervention
Compared to pure chlorine or salt pools, ozone/mineral systems are less expensive to maintain, pure and less chemically demanding.