Hot Tub Chlorine: Levels, Routine and Common Mistakes
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Time to read 4 min
If your hot tub water keeps turning cloudy, smelling strong, or losing chlorine overnight, you’re not alone. Most of the time it’s not a “big problem”—it’s just a small chlorine routine issue that snowballs.
This guide will help you understand hot tub chlorine in plain English, with simple steps for dosing, testing, shocking, and keeping your water stable.
Why Hot Tub Chlorine Matters (and why it can feel annoying)
Chlorine is your hot tub’s “cleaning crew.” It helps keep water safe by controlling the stuff you can’t see—like bacteria and gunk. The following chart should be able to help you:
| What Gets Into Your Hot Tub Water | When Chlorine is Working Right ✅ | When Chlorine Isn’t Working ❌ |
|---|---|---|
| Sweat | Clear water | Cloudy water |
| Body oils | Fresh-smelling water | Strong / “weird” odor |
| Lotions + sunscreen | Comfortable on skin | Itchy or irritated skin |
| Laundry detergent from swimsuits | Water feels relaxing | Chlorine “disappears” too fast |
| “Lots of friends in the tub” nights | Stable test strip results | Test strips don’t make sense |
Hot Tub Chlorine Types: What You Should Use
There are typically two types of chlorine your hot tub can take: chlorine granules and chlorine tablets.
| Type | Full Name | Common Form | Best For | Pros | Cons / Watch Outs |
|---|---|---|---|---|---|
| Dichlor | Sodium dichloro-s-triazinetrione | Granules | Hot tubs / spas | Dissolves fast, easy to dose, great for routine use | Adds CYA (stabilizer) over time, may require occasional drain/refill |
| Trichlor | Trichloro-s-triazinetrione | Tablets / pucks | Pools (mostly) | Slow-dissolving, convenient, long-lasting | Very acidic/strong, can cause pH issues and damage in hot tubs, also adds CYA |
💡 Let's Understand This
Dichlor contains a stabilizer called CYA (cyanuric acid).
Over time, too much CYA can make chlorine feel like it’s “not working” as well, which is why some owners eventually need a drain/refill.
Hot Tub Chlorine Levels & How to Measure
With the basics covered—what chlorine is, how it keeps your water clean, and the types you can use—let’s get into the recommended chlorine range for a safe, clear hot tub.
This is the part you came for: how much chlorine to add to hot tub without guessing.
Because every product is different strength, use this as a starting point, then adjust based on your test strip results. Here's a starter guide chart for granular chlorine
| Hot tub size | Light use (maintenance) | After heavy use |
|---|---|---|
| 200–300 gallons | small dose* | medium dose* |
| 300–400 gallons | small-medium dose* | medium-large dose* |
| 400–500 gallons | medium dose* | larger dose* |
Simple rule:
If you’re using the tub a lot, you’ll need more chlorine. If you’re barely using it, you’ll need less.
And yes—hot tubs can “eat” chlorine fast after big soak sessions. That’s normal.
*Generally, light maintenance is measured by the capful of the chlorine it comes with. A medium-heavier dosage might require multiple capfuls. Adhere to guidelines on the product's directions.
Watch Johnny Maintain this Swim Spa w/ Chlorine
The Sweet Spot: Hot Tub Chlorine Levels
People ask this all the time: “What should my chlorine level be?” Most hot tubs aim for a steady, safe range of chlorine that keeps water clean without feeling harsh.
Instead of obsessing over a single “perfect” number, focus on this:
Never let it sit at zero
Keep it stable
Adjust based on use (more people = more chlorine needed)
If your test strip reads zero, your water is basically unprotected—even if it looks clear (you can notice this in the video above where Johnny tests the swim spa).
At the end of the day, hot tub chlorine isn’t complicated… it just gets messy when you only deal with it after something goes wrong. If you keep it simple—test, dose, shock, clean your filter—you’ll have water that stays clear and feels good to soak in.
Hot Tub Chlorine FAQ
How often should I add chlorine to my hot tub?
This depends on your habits, but here’s the real-life answer:
A solid routine most people can stick to
Test 2–3 times a week
Add chlorine after you soak (especially after multiple people)
Shock weekly
Clean filter monthly (it matters more than people think)
Why does my hot tub smell like chlorine?
This is a big one. And the answer is surprising:
A strong smell often means your chlorine is working badly, not “too strong.”
What’s happening is usually a buildup of “used-up” chlorine compounds (people call them chloramines). The fix is usually:
shock the tub
improve circulation and filtration
check pH/alkalinity
My hot tub chlorine is reading zero, but I just added it...?
This is super common: hot tub chlorine reading zero.
Possible reasons:
your water has a lot of “demand” (it’s burning off fast)
you have a dirty filter / dirty water
your pH is too high so chlorine is less effective
test strips are old or not stored right
Quick fix:
test again
shock
clean/rinse filter
make sure pH is in a reasonable range
Hot tub chlorine is too high?
If you overdid it, don’t panic.
How to lower chlorine in hot tub:
open the cover
run jets with air on
let it naturally come down
avoid soaking until it’s back in a comfortable range
(And yes, sunlight helps, but hot tubs usually have covers on—so just airing it out does a lot.)
Hot tub chlorine is too low?
This happens when:
you’ve had heavy use
you waited too long between doses
your water is old
your filter is dirty
Fix:
add chlorine
shock if water is struggling
clean the filter
consider a water change if it’s been months and problems keep repeating
Can I use pool chlorine in my hot tub?
Short answer: usually not a great idea.
Hot tubs:
run hotter
have less water volume
are more sensitive to dosing and balance
If you want fewer headaches, use spa chlorine / dichlor for hot tub.
Shock vs Chlorine? What's the difference?
Chlorine = Kills Germs (Sanitizer)
Shock = clears out leftovers (oxidizer)
Shock helps remove the stuff chlorine struggles with, like:
body oils
lotion buildup
sweat waste
“used-up chlorine” compounds
Why is my hot tub water cloudy even though chlorine is “in range”?
Cloudiness often means filtration, oils, or leftover organics. Shock + filter cleaning helps a lot.
