How each disinfection system works, its advantages, its challenges, and which pools each one performs best in

Keeping the water disinfected is essential in any pool, residential or commercial.

Every pool needs chlorine or some other permitted oxidizing agent to remain safe: without proper disinfection, the water quickly becomes a breeding ground for bacteria, viruses, and algae. Chlorine has traditionally been the most used method for this purpose. The question facing those building or remodeling a pool is not whether to use chlorine, but how to get it into the water. Two paths dominate the market: traditional chlorination with trichlor (90% trichloroisocyanuric acid), in tablets or granules, and salt chlorination, which generates chlorine within the pool itself through electrolysis of salt (sodium chloride, NaCl) dissolved in water and the subsequent formation of hypochlorous acid (HClO) which acts as a powerful disinfectant.

Both systems end up producing the same disinfectant agent (hypochlorous acid), but they arrive at it through very different paths, with different implications in cost, convenience, maintenance, and automation. In this article, we compare both technologies to help you decide which one is best suited for your pool type and intended use.

Why every pool needs chlorine

Regardless of the system used, the disinfection work is carried out by the same compound: hypochlorous acid (HClO). This molecule penetrates the cell wall of bacteria, viruses, and algae and destroys their ability to reproduce, preventing diseases and infections associated with contaminated water.

The difference between trichlor and salt chlorination is not in what disinfects the water, but in how that chlorine is generated and replenished day by day.

Trichlor chlorination: the traditional method

Trichlor (trichloroisocyanuric acid) is one of the most concentrated forms of chlorine available, with about 90% available chlorine. It is applied in tablets, usually in a floating dispenser or with an in-line chlorinator. It is also used in granular form and dissolves gradually, releasing chlorine into the water.

A particularity of trichlor is that it incorporates isocyanuric acid, a stabilizer that protects chlorine from UV degradation: without a stabilizer, an outdoor pool can lose up to 35% of available chlorine per hour due to the sun. This same stabilizer, however, is the main source of long-term complications with this system and requires draining water to keep the isocyanuric acid concentration below healthy limits.

Salt chlorination: the self-sufficient system

A salt chlorinator does not add chlorine directly: it dissolves common salt (NaCl) in the water, usually between 3 and 5 kg per m³, and passes that water through an electrolysis cell powered by direct current. Inside the cell, the salt is transformed into free chlorine (hypochlorous acid), which disinfects the pool and then turns back into salt, closing the cycle. The system still needs pH control to function correctly.

How does electrolysis work?

 

The electrolysis process: dissolved salt is converted into free chlorine (HClO) and then returns to its salt form in a closed cycle.

The quality of salt: why not just any salt works

A common mistake is to think that for a salt chlorinator, any salt works the same. In practice, the purity of the salt is as important as the equipment itself: poor quality salt can affect both water clarity and the lifespan of the entire system.

Recommendation on salt type and use

Pool salt should be as pure as possible with the minimum amount of insolubles.

The technical recommendation is to use salt that is as pure as possible (over 99.8% NaCl), specifically formulated for pools (with the appropriate granulometry for uniform dissolution) and with the lowest possible amount of insolubles, ideally around 0.01%. When starting salt chlorination, between 3 and 5 kg of salt per m³ are dosed, and then only what is necessary is replenished to maintain that concentration according to the chlorinator manufacturer's specifications.

What are insolubles and why do they matter?

"Insolubles" are particles (sand, clay, or other minerals) that low-quality salt carries and that, unlike sodium chloride, do not dissolve in water. Using industrial salt, de-icing salt, coarse-grain salt not designed for pools, or even table salt with anti-caking additives, introduces these impurities directly into the circulation system.

Maintenance of the chlorinator "cell"

An encrusted electrolysis cell (left) versus a clean cell (right): salt quality directly influences the frequency of this maintenance.

An important detail: unlike chlorine, salt is not consumed during disinfection; it is only lost through splashes, filter backwashing, or dilution by rain, so impurities brought by poor-quality salt do not disappear over time, but tend to accumulate in the system with each replenishment. That's why it's worth investing in certified pool salt from the first fill, instead of trying to save money with generic salts of lower purity.

Trichlor vs. salt chlorination: direct comparison

Here's how both systems compare in the aspects that matter most to a pool owner:

 

How is a salt chlorinator sized and installed?

The equipment is installed in a bypass of the filtration system. Optionally, pH and ORP sensors can be installed to measure water quality before the chlorinator injects the generated chlorine back into the pool, thus optimizing its operation:

Where and how is a salt chlorinator installed?

Typical installation diagram of a salt chlorinator in the filtration circuit.

The equipment's production capacity (in grams of chlorine per hour) is calculated according to the pool's volume and daily filtration hours:

• Domestic use (up to 200 m³): Production (g/h) = 2 × Water volume (m³) ÷ Filtration time (h).
• Public or commercial use: the bather load is also added: Production (g/h) = [2 × Volume (m³) ÷ Filtration time] + [14 ppm × No. of users ÷ Filtration time].

As a reference, a minimum of 2 ppm of chlorine per m³ per day is recommended, and when the pool regularly exceeds 28 °C, it is advisable to use equipment with greater capacity, as heat accelerates chlorine consumption.

In which contexts is each system suitable?

Private residential pools: salt chlorination is usually the preferred option due to the comfort it offers swimmers and the possibility of almost completely automating daily maintenance.

Private pools with semi-public use (condominiums, boutique hotels): a properly sized salt chlorinator (considering the number of users) works well, supported by pH and ORP sensors to maintain stable water.

High-traffic public or commercial pools (clubs, resorts, large hotels): commercial-capacity salt chlorination equipment is available, sized for these flow rates, although in many cases they are evaluated alongside automated chlorination systems with trichlor or liquid hypochlorite, depending on the budget and the flow to be treated.

Temporary pools, intermittent use, or with a tight budget: traditional trichlor remains a valid option due to its low initial cost and because it does not require additional equipment installation.

As a complement: even pools with an installed salt chlorinator can occasionally use a traditional chlorine shock to treat contamination spikes or at the start of the season.

Conclusion

Trichlor and salt chlorination disinfect water using the same chemical principle, but they offer very different experiences for those who live with a pool day in and day out. Trichlor remains the option with the lowest initial cost and greatest simplicity, while salt chlorination requires a greater initial investment in exchange for softer water, less chemical handling, and the possibility of automating a large part of the maintenance. The best choice depends on the available budget, the type of pool, and how much manual control one is willing to take on; in any case, correctly sizing the equipment, whatever system is chosen, is key to keeping the water safe and well-balanced all year round.