Ask ten pool operators what chlorine they use and you’ll get four different answers — SDIC, TCCA tablets, calcium hypochlorite (“cal hypo”), or plain liquid bleach. Each has a legitimate use case, but choosing the wrong one costs 30-40% more per season, corrodes equipment, or leaves swimmers with red eyes. This guide gives you the specific decision matrix.
1. The Four Contenders at a Glance
| Chemistry | Available Cl | pH Effect | Stabilizer | Cost/kg Cl | Best For |
|---|---|---|---|---|---|
| SDIC | 60% | Neutral (pH 6.5-7.0) | Yes (CYA) | US$1.83 | Outdoor pools, spa |
| TCCA | 90% | Acidic (pH 2.7-3.5) | Yes (CYA) | US$1.50 | Large outdoor pools |
| Cal Hypo | 65-70% | Alkaline (pH 11-12) | No | US$1.75 | Shock treatment, indoor |
| Liquid Bleach | 10-15% | Alkaline (pH 12-13) | No | US$3.20 | Small residential, indoor |
2. Decision Matrix by Pool Type
Outdoor Residential Pool (10-30 m3)
Winner: TCCA tablets (200g) — slow-release matches sun-driven chlorine loss, stabilized by built-in CYA to survive UV. One 200g tablet per week per 20 m3 keeps residual at 1-2 mg/L. Cost per year for a 20 m3 pool: about US$80.
Public / Hotel Pool (50-500 m3)
Primary: TCCA + weekly SDIC shock — automatic feeder loaded with TCCA maintains baseline; SDIC (fast neutral pH) used weekly at 5-10 mg/L to break down chloramines and organics. Combination reduces total chemical cost by 22% vs pure Cal Hypo.
Water Park (>1000 m3)
Winner: Chlorine gas or liquid sodium hypochlorite bulk feed — economies of scale favor Cl2 gas (US$0.60/kg equivalent) but require permits, safety systems, dedicated operators. Only reason to consider TCCA/SDIC here is if permit is impossible.
Indoor Chlorinated Pool
Winner: Cal Hypo or liquid bleach — no UV degradation means no need for stabilizer. Cal Hypo shock at 5 mg/L weekly to prevent chloramine buildup that causes “pool smell”. Avoid TCCA/SDIC because their CYA content locks up chlorine unnecessarily indoors.
Saltwater Pool
Winner: Salt chlorinator + SDIC shock for algae events — salt cell generates Cl in situ but occasional SDIC shock is cheaper than replacing salt cell for algae emergencies.
3. Cost of Ownership – 5 Year Analysis (25 m3 outdoor pool)
| Chemistry | 5-year Cost | Equipment Wear | Total 5-year |
|---|---|---|---|
| TCCA 200g tablets | $420 | Minimal | $420 |
| SDIC granules | $540 | Minimal | $540 |
| Cal Hypo shock | $680 | Scale buildup +$150 | $830 |
| Liquid bleach | $920 | Alkaline erosion +$300 | $1,220 |
4. Water Balance Impact
The pH swing is invisible to the naked eye but costs real money:
- TCCA (pH 2.7-3.5): drives pool pH down; you spend on soda ash to raise it back
- SDIC (pH 6.5-7.0): neutral, no pH adjustment needed
- Cal Hypo (pH 11-12): raises pH; you spend on muriatic acid to lower it
- Bleach (pH 12-13): highest pH drift; same acid demand as Cal Hypo
For a 100 m3 hotel pool using TCCA, annual soda ash spend is around US$140. Using SDIC eliminates this entirely.
5. Common Mistakes with Each Chemistry
- TCCA in indoor pool — CYA builds up over years, chlorine locks up, pool becomes ineffective. Requires full drain every 3-4 years.
- Cal Hypo in TCCA feeder — chemical incompatibility, feeder corrodes and can explode.
- Mixing bleach with anything acidic — releases toxic Cl2 gas. Killed a pool operator in Ohio (2022).
- SDIC without pool cover overnight — chlorine burns off in 12-24 hours due to lack of CYA saturation.
6. FAQ from Pool Operators
Q: Can I switch chemistries mid-season?
A: Yes, but flush the feeder and adjust water balance first. Switching from Cal Hypo to TCCA requires pH drop; from TCCA to Cal Hypo requires soda ash prep.
Q: Why does my TCCA smell so much stronger than SDIC?
A: TCCA releases chloramines faster in acidic environment. Your CYA may be too high (>100 mg/L) or pH too low.
Q: Is Cal Hypo actually cheaper than TCCA if I include shipping to Africa/LATAM?
A: No. Cal Hypo has only 65% active Cl and reacts with moisture, so shipping is 30% costlier per kg-Cl-delivered.
Q: What is the cheapest chlorine per kg of ACTIVE chlorine delivered to my port?
A: TCCA 90% at US$1.35/kg FOB = US$1.50 per kg-active-Cl. Cal Hypo 68% at US$1.20/kg = US$1.76 per kg-active-Cl. TCCA wins by 15%.
Sourcing SDIC/TCCA from Verified Manufacturer
Shilan Chemical produces both SDIC and TCCA at NSF-listed facility in Hebei, China. Volume discounts, mixed pallets available for distributors. See our full product range → or read our detailed SDIC vs TCCA comparison.