Chlorine and bromine get all the attention when people talk about hot tub maintenance, especially when deciding how many chlorine tablets in a SaluSpa are needed to maintain safe water, but pH and alkalinity are honestly the bit that actually decides whether your sanitiser even works. Get hot tub pH and alkalinity wrong and you can dose chemicals perfectly and still end up with cloudy water, skin irritation, or a tub that smells off despite “correct” chlorine readings.
This guide walks through what these two numbers actually mean, how they fit into overall hot tub water chemistry, and how to keep them where they need to be.
Maintaining Hot Tub pH and Total Alkalinity
Ideal Ranges at a Glance
| Measurement | Ideal Range |
|---|---|
| pH level | 7.2–7.6 |
| Total alkalinity | 80–120ppm |
| Chlorine/bromine | 3–5ppm |
Alkalinity should be checked and adjusted before pH, not after it acts as a buffer, so getting it right first makes pH far easier to stabilise.
What pH Actually Does
The pH scale runs from 0 (very acidic) to 14 (very alkaline), with 7 being neutral. Hot tub water needs to sit slightly above neutral, around 7.2-7.6, because:
- Too low (acidic) and it irritates skin and eyes, and corrodes metal fittings and the pump over time
- Too high (alkaline) and chlorine/bromine become far less effective at killing bacteria, regardless of how many bromine tablets for a SaluSpa you add.
- Either extreme can cause cloudy water even when sanitiser levels look fine on a test strip
What Total Alkalinity Actually Does
Total alkalinity is essentially a buffer that stops pH swinging wildly every time you add chemicals or people get in. Without it sitting in the right range, pH becomes almost impossible to keep stable.
| Alkalinity Level | What Happens |
|---|---|
| Below 80ppm (low) | pH swings rapidly, hard to control |
| 80-120ppm (correct) | Stable buffer, pH stays manageable |
| Above 120ppm (high) | pH gets “locked” too high, hard to lower |
Signs of Low Alkalinity
- pH bounces around even after you’ve just adjusted it
- Water can feel slightly more irritating on skin and eyes
- Metal fittings or the pump housing may show early corrosion signs
- Chemical doses seem to “not hold” between tests
Signs of High Alkalinity
- Cloudy or hazy water despite chlorine/bromine reading normal can also indicate it’s time to review how often to change a SaluSpa filter.
- pH stuck stubbornly high no matter how much pH decreaser you add
- Scaling or white residue building up on tub surfaces
- Sanitiser seems less effective than it should be
Step-by-Step: Balancing Alkalinity First
- Test total alkalinity using a proper water testing kit, not just a basic pH strip
- If it’s below 80ppm, add an alkalinity increaser following the product’s dosing guide
- If it’s above 120ppm, this is harder to lower directly often easier to partially drain and refill with fresh water
- Re-test after a few hours of circulation before moving on to pH
- Only adjust pH once alkalinity is sitting in range
Step-by-Step: Balancing pH After Alkalinity
| Step | Action |
|---|---|
| 1 | Test pH after alkalinity is confirmed in range |
| 2 | If pH is below 7.2, add a pH increaser |
| 3 | If pH is above 7.6, add a pH decreaser |
| 4 | Circulate for 30+ minutes before retesting |
| 5 | Repeat in small doses rather than over-correcting |
Always dose gradually overcorrecting pH in one go is one of the most common mistakes and just sends it swinging the other way.
A Simple Testing Routine
| Task | Frequency |
|---|---|
| Test pH and alkalinity together | 2-3 times weekly |
| Adjust alkalinity if needed | As soon as it drifts out of range |
| Adjust pH if needed | After alkalinity is confirmed correct |
| Full water change | Every 3-4 months, or sooner if alkalinity stays high |
Common Mistakes People Make
- Adjusting pH before checking alkalinity, which undoes the fix within a day or two
- Adding too much pH increaser or decreaser at once, overshooting the target range
- Assuming clear water means balanced water is a mistake, because even after learning how to clean a SaluSpa, water can still be chemically unbalanced.
- Forgetting that heavy use (more bathers, hot weather) shifts both readings faster than expected
FAQs
What’s the ideal pH level for a hot tub?
Between 7.2 and 7.6 is the standard target range.
Should I fix alkalinity or pH first?
Always alkalinity first, since it acts as a buffer that stabilises pH afterwards.
What happens if alkalinity is too high?
pH gets harder to lower and you may see cloudy water or scaling, even with sanitiser balanced.
Can I use the same test strip for both pH and alkalinity?
Yes, most multi-test strips check both, but a dedicated test kit gives more accurate readings.
How often should I test pH and alkalinity?
2-3 times a week, more often after heavy use or adding fresh water.
Conclusion
Getting hot tub pH and alkalinity right isn’t complicated once you know the order matters alkalinity first, pH second, always in small adjustments rather than big corrections. Get this pair stable and your sanitiser actually does its job properly,
which solves a lot of the cloudy water and irritation issues people otherwise blame on chlorine or bromine alone. Want a hot tub that makes water testing part of an easier routine? Browse our inflatable hot tub range, including the Corsica and Tahiti.
