Which Chlorine Should You Use? Ranked by What Else It Puts in Your Water
Every chlorine source delivers the same active sanitizer — the difference is what else comes with it. Liquid chlorine (and plain bleach — the identical chemical, just weaker) add nothing that accumulates, so they're the best daily choice: you set CYA once and control it. A salt system is the same idea, generating that chlorine on-site. The convenient ones carry baggage that builds up: trichlor tablets add CYA and acid (the slow road to 'chlorine lock'); dichlor adds CYA; cal-hypo adds calcium (scale). Use liquid or salt as your daily driver; reach for tablets or cal-hypo deliberately, when you actually want the thing they add.
Walk into a pool store and there’s a wall of chlorine: jugs, buckets of tablets, bags of shock, granular tubs. They all deliver the same active sanitizer once dissolved. So the choice isn’t really “which chlorine kills better” — it’s which one adds the least junk you’ll have to deal with later. Rank them that way and the answer falls out.
The only question that matters: what else does it add?
Chlorine you dose all the time. The other things a sanitizer can carry — stabilizer (CYA), calcium, acid — you want to set once and hold steady, because they accumulate. The best chlorine source is the one that adds nothing to accumulate.
| Source | Strength | To raise 10 ppm FC in 10,000 gal | pH effect | Also adds | Best used as |
|---|---|---|---|---|---|
| Liquid chlorine (sodium hypochlorite) | 10–12.5% | ~107 fl oz (¾ gal) at 12.5% | ~Neutral over a cycle | Trace of salt | Daily driver |
| Bleach (sodium hypochlorite) | 6–8.25% | ~162 fl oz (1.3 gal) at 8.25% | ~Neutral over a cycle | Trace of salt — same as liquid, weaker | Daily, small pools/spas |
| Salt / SWG | generated | Set output %, not a dose | Drifts up over time | Nothing new — it is chlorine | Daily, hands-off |
| Trichlor (tablets) | ~90% | ~18 oz, slow-release in a feeder | Lowers pH & TA | CYA + acid | Deliberately, or vacations |
| Dichlor (granular) | ~56–62% | ~22 oz at 62% | Slightly lowers | CYA | Startup / raising CYA |
| Cal-hypo (granular) | ~50–73% | ~19 oz at 70% | Raises pH | Calcium | Occasional, or if CH is low |
| Lithium hypo | ~35% | Not worth dosing | Slightly raises | Little, but very expensive | Skip |
Liquid amounts are fluid ounces; granular amounts are weight. Doses are for a 10 ppm free-chlorine bump in 10,000 gallons — compute the exact amount for your pool and product. Trichlor and dichlor stir stabilizer in with every dose, so they’re feeder and startup tools, not everyday shock.
The winners: liquid chlorine and salt
Liquid chlorine adds only a little salt and nets out roughly pH-neutral over a full cycle, so it changes nothing you have to chase. You add CYA separately, once, to the level you want, and control it independently. That’s the whole philosophy of this site: keep your variables separate so each one is easy to manage.
A salt chlorine generator is the same logic, automated — it makes that exact chlorine on-site from dissolved salt, continuously. It isn’t “chlorine-free” (a common myth); it’s just liquid-chlorine chemistry with a machine doing the pouring. Its one quirk is an upward pH drift you manage with acid — see why a salt pool scales.
Plain bleach is the exact same chemical as liquid chlorine, just more dilute — not a hack, not a downgrade. It gets its own myth-buster because so many people are told it’ll wreck a pool. It won’t.
The convenient ones, and the baggage they carry
Trichlor tablets are the classic trap. They’re effortless in a floater or feeder — and every puck adds CYA and is acidic. Over a season CYA climbs, and because sanitizing power is tied to the FC/CYA ratio, you need ever more chlorine to keep up until it feels like the chlorine quit. That’s over-stabilization — the real story behind “chlorine lock” — and the only fix is draining and refilling.
Cal-hypo adds calcium every dose. In hard-water Florida that hardness concentrates and can scale your surfaces, heater, and cell.
None of these are “bad.” They’re tools with a side effect — good when you actually want the thing they add:
- Dichlor at startup, to raise chlorine and CYA together to your target.
- A few trichlor tablets before a vacation, or early season to nudge CYA up on purpose (then stop before it overshoots).
- Cal-hypo for a quick granular dose, or when your calcium hardness is genuinely low and you want to bring it up.
Use the side effect on purpose, or don’t invite it.
If you’re buying one of them, buy it knowing the strength
The percentage on the bag is the whole story, and it is the thing these products are worst at telling you. Shock is sold anywhere from 47% to 78%, so the sticker price says almost nothing about what a dose actually costs.
The dosing for any of these is on the chemical dosing calculator, which now sizes the package to your dose — and tells you when the honest answer is to buy it locally instead.
Choose the right tool for the job
Every source above is the right answer to some question. Match the tool to what you’re actually trying to do:
| Your goal | Reach for | Why |
|---|---|---|
| Add chlorine fast (shock, algae, after a crowd) | Liquid chlorine, or cal-hypo | Both dissolve fast and hit FC now; liquid adds nothing lasting, cal-hypo adds calcium |
| Chlorinate and set CYA at startup | Dichlor | Raises FC and stabilizer together to your target in one product |
| Raise CYA on purpose (early season, or nudging it up) | Trichlor or dichlor | Both carry stabilizer — trichlor drip-feeds it from a floater or feeder |
| Raise calcium while you chlorinate | Cal-hypo | Every dose adds calcium hardness — a feature when your CH is genuinely low |
| Hands-off steady residual, day to day | Salt system, or liquid chlorine | Salt makes it continuously; liquid is the no-baggage manual daily driver |
| Cover a week away (vacation) | Trichlor tabs in a feeder | Slow-release holds FC while you’re gone — just expect some CYA creep |
The through-line: use a source when the thing it adds is the thing you want. Reach for trichlor when you want stabilizer and cal-hypo when you want calcium — not as your everyday habit, or you’ll spend the summer chasing the number it quietly ran up. When you just want clean water and nothing else moving, that’s liquid or salt.
See the trade-off for your pool
Pick how much free chlorine you want to add and watch the hidden cost of each source, head to head — the CYA that trichlor piles on, the calcium from cal-hypo, the trace of salt from liquid.
The Chlorine Showdown
Same free-chlorine boost, four ways — and the hidden cost each one quietly adds. Pick how much FC you want to add and see who wins.
Don't know your gallons? Work it out here →
Exact geometry at 7.48 gal/ft³. Kidney shapes, diving hoppers, litres and salt/turnover figures live in the full Pool Volume Calculator.
Preview any other dose
See every number a move touches before you commit — the secondary effects included.
The honest bottom line
There’s no magic chlorine — they’re the same sanitizer wearing different packaging and price tags. Pick your daily source for what it doesn’t add: liquid chlorine or a salt system. Keep tablets and cal-hypo in the cabinet for the specific jobs where their baggage is the point. Do that and you’re not fighting rising CYA or creeping calcium all summer — you’re just holding free chlorine at the target for your CYA and letting it work. That’s less is more.
Shopping a salt system so the pouring’s automatic? Our salt water chlorinator showdown compares the cells and their real running costs.
Frequently asked
What is the best type of chlorine for a pool?
For day-to-day sanitizing, liquid chlorine (sodium hypochlorite) or a salt chlorine generator, because they add only chlorine and a trace of salt — nothing that accumulates. That lets you set cyanuric acid (CYA/stabilizer) to your target once and keep it there. Tablets (trichlor) and granular cal-hypo work, but each dose also adds stabilizer or calcium, which build up over a season and create their own problems. The 'best' chlorine is the one that doesn't change two other numbers every time you use it.
What's the difference between liquid chlorine and chlorine tablets?
Both sanitize the same way, but they carry different extras. Liquid chlorine (sodium hypochlorite) adds only a little salt and is roughly pH-neutral over a full cycle, so nothing accumulates. Trichlor tablets are convenient in a floater or feeder, but every tablet also adds cyanuric acid (stabilizer) and is acidic — so over weeks your CYA climbs and your pH and alkalinity fall. Tablets are a fine tool used on purpose; they're a trap used as your only source.
Are chlorine tablets bad for your pool?
Not bad, but not neutral. Trichlor tablets slowly raise CYA (stabilizer) with every puck. As CYA climbs, you need more free chlorine to keep the same sanitizing power (the FC/CYA ratio), until it feels like your chlorine 'stopped working' — that's over-stabilization, sometimes called chlorine lock, and the only real fix is diluting with fresh water. Tablets are useful for vacations or for intentionally nudging CYA up early in the season; they're just a poor everyday habit.
Saltwater vs chlorine pool: which is better?
This is the most common false choice in pool ownership, because a saltwater pool IS a chlorine pool. A salt cell takes the salt already dissolved in the water and electrically converts it into the exact same sanitizer — hypochlorous acid — that comes out of a jug of liquid chlorine. Nobody is swimming in a chlorine-free pool; the difference is only in how the chlorine gets there. So judge it on three practical things instead. CONVENIENCE, where salt genuinely wins: the cell makes chlorine continuously, so you stop hauling and dosing jugs, and the water feels softer and smells less because you are not riding the spikes and troughs of manual dosing. COST, where salt does NOT win the way it is sold: over the life of the system a salt pool lands roughly even with liquid chlorine and usually costs a bit MORE than cheap trichlor tablets, because the cell is a consumable rated in operating hours that eventually needs a several-hundred-dollar replacement. Buy salt for the convenience, not the savings — and be suspicious of anyone selling it on savings alone. MAINTENANCE, where it is a wash: a salt pool still needs testing, still needs acid, and still needs its stabilizer watched, so it is not a hands-off pool. The real decision is not salt versus chlorine, it is which chlorine SOURCE fits how you want to spend your time — and if you go manual, this guide ranks the sources by what each one adds to your water besides chlorine, which is the part that actually decides.
Is cal-hypo or liquid chlorine better?
For regular use, liquid chlorine, because cal-hypo (calcium hypochlorite) adds calcium hardness every dose. In hard-water areas that calcium builds up and can scale your surfaces, heater, and salt cell. Cal-hypo has its place — a quick granular dose, or when your calcium is genuinely low and you want to raise it — but as a daily sanitizer it slowly hardens your water. Liquid chlorine adds only a trace of salt, so nothing accumulates.
Does the type of chlorine affect pH?
Yes. Liquid chlorine and bleach are roughly pH-neutral over a full cycle (basic going in, then the chlorine's reaction gives the acidity back). Trichlor tablets are distinctly acidic — they lower pH and alkalinity, so heavy tablet users fight low pH. Dichlor is close to neutral. Cal-hypo is mildly basic and adds calcium. A salt pool's chlorine reaction is about neutral, but salt pools drift pH up over time from the cell's aeration — a separate effect.
How much chlorine do I need to add to raise free chlorine?
It depends on the source and your pool's size. As a rule of thumb for a 10 ppm free-chlorine bump in 10,000 gallons: about 107 fluid ounces (three-quarters of a gallon) of 12.5% liquid chlorine, roughly 19 ounces of 70% cal-hypo, or about 22 ounces of 62% dichlor. Liquid amounts are fluid ounces and granular amounts are weight, and each source also nudges another number — dichlor adds stabilizer (CYA), cal-hypo adds calcium. Scale to your own gallons, or use our chemical dosing calculator, which takes your pool size and the exact product strength and returns the amount plus the side effect.