Trichlor tablets are convenient but steadily raise CYA, driving down chlorine effectiveness. For coastal pools near Oak Island, liquid chlorine or a salt chlorine generator is the better long-term choice. Never place tablets in the skimmer because the extreme acidity corrodes pumps and heaters.
What Is Trichlor?
Trichloroisocyanuric acid (trichlor) is a stabilized form of chlorine pressed into slow-dissolving tablets. The Pool & Hot Tub Alliance (PHTA) notes that trichlor has a pH of approximately 2.8 to 3.0, making it extremely acidic. It's popular because it's convenient. Drop tablets in a floater or chlorinator and forget about it. However, this convenience comes with trade-offs that many pool owners don't understand until they cause problems.
What Are the Advantages of Trichlor Tablets?
- Convenience: Slow-dissolving, requires less frequent attention
- Built-in stabilizer: Helps chlorine resist UV degradation
- Economical: Lower upfront cost than liquid chlorine
- Long shelf life: Stores well for extended periods
- No special equipment: Works with simple floaters
What Are the Drawbacks of Trichlor Tablets?
Critical: Extremely Acidic
Trichlor tablets have a pH of 2.8, approximately 10,000 times more acidic than plain water. This acidity causes significant damage when concentrated in one location.
- Stabilizer accumulation: Tablets are 55% cyanuric acid. Over time, CYA builds up leading to "chlorine lock"
- pH depression: Continuously lowers pH, requiring frequent acid/base adjustments
- Bleaching: Can bleach pool surfaces if left in contact (floater settling in one spot)
Never Put Tablets in the Skimmer
This is one of the most damaging practices in pool care. Here's why:
- 1Water flowing through the skimmer becomes highly acidic
- 2This acidic water flows directly through your pump
- 3Then through your heater (if equipped)
- 4Corroding seals, gaskets, and heat exchangers
- 5Can destroy a heater in 1-2 seasons
If you must use tablets: Use an inline chlorinator or a floating dispenser, never the skimmer basket.
Why Do Trichlor Tablets Raise CYA Over Time?
Because trichlor contains cyanuric acid (CYA), every tablet adds to your stabilizer level. This accumulates over time:
- Optimal CYA: 30-50 ppm
- Problem zone: 70-100+ ppm
- At high CYA, chlorine becomes less effective (chlorine lock)
- The only solution is partial water replacement
Pools using tablets exclusively often need to drain and refill 30-50% of their water annually to reset CYA levels.
What Are Better Alternatives to Trichlor Tablets?
Liquid Chlorine
Adds no stabilizer. pH neutral after off-gassing. Professional choice for ongoing sanitation.
Salt Chlorine Generator
Creates pure chlorine from salt. No CYA addition. Consistent, steady chlorine production.
Frequently Asked Questions
Why does my CYA keep rising?
Every time you add trichlor tablets or dichlor granular chlorine, you are also adding cyanuric acid (trichlor is 55% CYA by weight). As CYA accumulates above 80-100 ppm, it suppresses chlorine's oxidation potential to the point where adequate sanitation becomes impossible, a condition called chlorine lock. The CDC Model Aquatic Health Code sets 100 ppm as the maximum safe CYA level for managed pools. Switching to liquid chlorine or a salt system stops CYA accumulation entirely.
Can I put chlorine tablets in my skimmer basket?
Please avoid doing this. Tablets have a pH of 2.8 (extremely acidic). When placed in the skimmer, concentrated acidic water flows directly through your pump and heater, causing corrosion and shortening equipment life significantly.
Why do tablets raise my stabilizer (CYA) level?
Trichlor is 55% cyanuric acid by weight. Every pound of tablets adds about 6 ppm of stabilizer to 10,000 gallons of water. Over time, this accumulates and can lead to chlorine lock.
What's the alternative to tablets?
Liquid chlorine (sodium hypochlorite) adds no stabilizer and is pH neutral after gassing off. Salt systems generate pure chlorine. Both are preferred by professionals for long-term pool health.