Hot Tub Chemistry: Facts & Common Questions
1. The Core Basics
Q: What are the 4 main things I should care about?
- Sanitizer (keeps water safe)
- pH (how acidic/basic the water is)
- Total Alkalinity (TA) (buffers/stabilizes pH)
- Calcium Hardness (CH) (protects surfaces & equipment)
Ideal ranges
- Chlorine or Bromine: 3–5 ppm
- pH: 7.2–7.8 (sweet spot ~7.4–7.6)
- Total Alkalinity: 80–120 ppm
- Calcium Hardness: 150–250 ppm (some guides say up to 400 ppm is fine)
2. Sanitizer: Chlorine vs Bromine
Q: Which is better for a hot tub, chlorine or bromine?
Chlorine – pros:
- Works fast, very effective sanitizer
- Cheap and easy to find
- Familiar and widely used
Chlorine – cons:
- Smell can be stronger if not managed well
- Breaks down faster in hot water than bromine
- Can be more irritating if levels swing a lot
Bromine – pros:
- More stable in hot water (great for hot tubs)
- Less “chlorine pool” smell
- Stays active longer and is gentler for some people
Bromine – cons:
- Usually more expensive
- Slower to build up level at start
- Once you go bromine, you generally stay bromine (same tub) unless you drain and start over
Bottom line 98% of our customers use the Care Free System for its simplicity.
3. pH: Why It Matters
Q: What happens if my pH is too low or too high?
*pH too low (below 7.2):
- Water is more acidic
- Can irritate eyes/skin
- Corrodes metal parts and heater
- Water feels dull or cloudy
- Scale buildup on shell, heater, jets
- Sanitizer (chlorine/bromine) becomes less effective
- Can cause “ring” or rough surfaces, Can damage seals over time
Q: How do I adjust pH correctly?
- Test water with strips or a test kit.
- If pH is low, add pH Plus
- If pH is high, add pH Minus
- Add in small amounts, let it circulate 20–30 minutes, then retest.
⚠️ Tip: Always adjust Total Alkalinity first, then fine‑tune pH.
4. Total Alkalinity
Q: What does alkalinity actually do?
Think of TA as a shock absorber for pH:
- Low TA → pH bounces all over the place.
- High TA → pH is hard to move and tends to creep upward.
Q: What if my TA is off?
- Low TA (<80 ppm):
- pH swings a lot (hard to keep stable)
- Can be corrosive to equipment over time
- High TA (>120–150 ppm):
- pH hard to adjust
- Scaling and cloudy water risk
Q: How do I adjust TA?
- To raise TA: add Resist
- To lower TA: add pH Minus or Relent
Aerate the water (run jets, blowers) to help pH rise back while TA gradually comes down.
5. Calcium Hardness
Q: Why does calcium matter?
- Too low CH (<150 ppm):
- Water becomes “hungry” and can pull minerals from metal parts and surfaces (corrosion/etching).
- Too high CH (>300–400 ppm):
- Scale on heater, jets, waterline
- Cloudy water and rough surfaces
Q: How do I adjust CH?
- To raise CH: use a Protect.
- To lower CH:
- There’s no simple chemical “decreaser” for calcium.
- Usually: dilute by partially draining and refilling with softer water.
6. Shock: What, Why, How Often?
Q: What does “shocking” the hot tub mean?
“Shock” means adding a strong oxidizer to:
- Burn off organic contaminants (body oils, sweat, lotions, etc.)
- Clear up dull or slightly cloudy water
- Reduce chloramine/bromamine (smelly combined sanitizer)
Types of shock
- CareFree Boost
- CareFree
- Ultra Shock
- Clean & Clear
Q: How often should I shock?
- Typical use: 1× per week
- More often if:
- Heavy usage
- Party/guests
- Strong smell or slight cloudiness
Always run pumps with cover open when shocking, and follow label doses.
7. Foam, Cloudiness & Smell
Q: Why is my hot tub foamy?
Common causes:
- Soap from swimsuits, detergents, shampoo
- Body lotions, hair products, deodorant
- Low calcium hardness or imbalanced water
- Old/dirty water close to change time
What to do:
- Scoop large foam with a skimmer.
- Check and balance pH, TA, CH.
- Shock the tub.
- Clean or replace filters.
- If foam returns quickly and water is old → drain and refill.
Q: Why is my water cloudy?
- High pH or high TA
- High calcium + high pH (scaling/precipitation)
- Poor filtration (dirty or old filters)
- Not enough sanitizer or shock
Fix:
- Test and balance chemistry.
- Shock the water.
- Run filtration longer (and jets).
- Clean filters thoroughly.
- If still bad → partial or full drain/refill.
Q: Why does it smell strong, like a public pool?
Often that “chlorine smell” is actually combined chlorine/bromine, meaning:
- Not enough fresh sanitizer
- Need shock, not less chlorine/bromine
Do:
- Shock the tub
- Make sure sanitizer is in range
- Open cover and allow gases to vent
8. Draining & Refilling
Q: How often should I change all the water?
General rule of thumb:
- About every 3–4 months
Change sooner if:
- Chemistry is constantly hard to control
- Persistent smell or cloudiness
- Heavy use or lots of bathers
When refilling:
- Fill through the filter area
- Once full, run pumps to purge air.
- Add Eliminate if you have hard water.
- Then follow the Beachcomber Start up sheet you received your tub.