"What is the best type of chlorine for a pool?" The honest answer is: the one whose side effects your water can take. Every type delivers chlorine; they differ in what they leave behind.
The short answer: trichlor (tablets) and dichlor (granules) add stabilizer and lower pH. Cal-hypo adds calcium. Liquid chlorine adds only a small amount of salt. TroubleFreePool's pick is liquid chlorine or a salt chlorine generator. Tablets can still suit you if your pool needs stabilizer and you test it regularly (our note).
Part of: Pool Chlorine: Types, Levels and How to Keep Them Steady, our overview of every chlorine question.
The types compared
| Type | Usual form | Also adds | Watch out for |
|---|---|---|---|
| Trichlor | 3-inch tablets | Stabilizer (CYA); lowers pH | CYA builds up |
| Dichlor | Granules (our note) | Stabilizer (CYA); lowers pH | Can raise CYA very quickly |
| Cal-hypo | Usually powder | Calcium (about 1/3 of the product) | Calcium cannot be taken out |
| Liquid chlorine | Liquid (6%, 10%, 12.5%) | A small amount of salt | Loses strength in storage |
All from TroubleFreePool's "How to chlorinate your pool" and "Recommended pool chemicals".
Which one for your pool?
- Stabilizer already 50 ppm or more: liquid chlorine, so CYA stops climbing (our advice, from TroubleFreePool's CYA warnings). See chlorine tablets and stabilizer.
- New outdoor pool with no stabilizer yet: tablets or dichlor add it as you go, or add stabilizer once with the stabilizer calculator and use liquid.
- Calcium already high: avoid cal-hypo.
- Hot tub: the CDC recommends not using cyanuric acid or chlorine products with cyanuric acid (dichlor, trichlor) in hot tubs.
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Raises free chlorine Liquid chlorine (sodium hypochlorite)Sold as "liquid chlorine" or "chlorinating liquid". Check the strength (%) on the label: the dose depends on it. Shipping rules differ by product and state.
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Slow-release chlorine 3-inch chlorine tablets (trichlor)Stabilized tablets for a floater or feeder. They add stabilizer (CYA) as they dissolve: test CYA regularly. Use the dose on the label of the product you buy.
FAQ
What's the difference between chlorine and pool chlorine?
"Pool chlorine" is a product that releases chlorine into the water; the types above are different chemicals that do that. Liquid pool chlorine is the same chemical as household bleach, only stronger (TroubleFreePool). See is pool chlorine just bleach?
Sources
- TroubleFreePool: How to chlorinate your pool (what each type adds, best options)
- TroubleFreePool: Recommended pool chemicals (liquid strengths, same as bleach)
- CDC: Home pool and hot tub water treatment and testing (no stabilized chlorine in hot tubs)
Sources read on November 4, 2026. Product labels change: the label on the product you buy always wins.
