Balanced water is the foundation of everything else in hot tub ownership. It makes sanitizer work properly, keeps the water comfortable on skin, protects equipment from corrosion and scaling, and reduces how much you need to intervene on a weekly basis. The process is not complicated, but the order matters — and most problems come from people skipping steps or doing them in the wrong sequence.
Why order matters
The four parameters of water balance — alkalinity, pH, calcium hardness, and sanitizer — interact with each other. Alkalinity buffers pH. pH affects how well sanitizer works. Calcium hardness influences pH stability and scaling risk. If you try to set pH before alkalinity, you will fight the chemistry the whole way. If you add sanitizer before pH is right, you will waste half of it.
The correct sequence is: alkalinity first, then pH, then calcium hardness, then sanitizer. Follow that order on a fresh fill or after a water change, and balancing goes quickly. Skip the order, and you can spend hours adding and readjusting without landing anywhere stable.
Step 1: Total alkalinity — 80 to 120 ppm
Total alkalinity is the pH buffer. When it is in range, pH resists sudden swings and stays where you set it. When it is off, pH bounces around and every adjustment overshoots.
Test alkalinity first. If it is below 80 ppm, add sodium bicarbonate (alkalinity increaser) dissolved in a bucket of warm water and poured around the tub with the jets running. Wait 30 minutes, then retest. If it is above 120 ppm, add sodium bisulphate (pH decreaser) in small doses — this lowers both alkalinity and pH simultaneously, so do it in increments to avoid overcorrecting.
Do not move to pH until alkalinity is inside the 80–120 ppm range. For more detail on what alkalinity does and how to adjust it, see our alkalinity guide.
Step 2: pH — 7.2 to 7.8
pH measures how acidic or basic the water is on a scale of 0 to 14. The target for hot tubs is 7.2 to 7.8, with 7.4 to 7.6 being the sweet spot. Below that range the water is acidic, which irritates eyes and skin and corrodes equipment. Above that range, the water is basic, which reduces chlorine effectiveness and encourages calcium scaling.
Once alkalinity is in range, adjusting pH usually requires smaller doses and holds better. Use pH increaser (sodium carbonate or sodium bicarbonate) to raise it, or pH decreaser (sodium bisulphate) to lower it. Add in small amounts, circulate for 15–20 minutes, and retest before adding more. Fresh tap water and refilled tubs often run higher than ideal, so plan to add pH decreaser more often than increaser on a new fill.
Fresh tap water in Alberta and Saskatchewan is often quite high in alkalinity and pH due to naturally hard, mineral-rich municipal water sources. Test immediately after filling and expect to spend some time lowering both before adding sanitizer. This is normal and goes faster once you have done it once.
Step 3: Calcium hardness — 150 to 250 ppm
Calcium hardness measures how much dissolved calcium is in the water. Low calcium water is "soft" and aggressively strips calcium from surfaces — it will attack grout, metal fittings, and equipment to satisfy its mineral demand. High calcium water is "hard" and deposits calcium scale on the shell, heater, and jets.
The target range for hot tubs is 150 to 250 ppm. In most Prairie municipalities, tap water is already on the harder side, so you are more likely to be adjusting downward or holding in range than raising it.
- Too low (below 150 ppm): Add calcium chloride (calcium hardness increaser) dissolved in warm water. Add slowly — calcium hardness is difficult to lower and overdosing creates a bigger problem than underdosing.
- Too high (above 250 ppm): There is no easy chemical fix. Diluting with fresh water is the main option. For very hard water, a partial drain-and-refill with softer water (or filtered water) is the most effective approach.
Step 4: Sanitizer — chlorine at 3 to 5 ppm
Sanitizer is added last because it only works properly when the other three parameters are in range. Chlorine added to water that is too acidic or too basic is less effective and breaks down faster, which means you use more of it and still get less protection.
For hot tubs, the target free chlorine level is 3 to 5 ppm. Add granular dichlor (sodium dichloro-s-triazinetrione) measured per the manufacturer's instructions for your tub's volume. Circulate for 30 minutes, then test and adjust if needed.
After the initial balance on a new fill, ongoing sanitizing is much simpler — typically a tablespoon of chlorine every one to two weeks on an Eco Spa, thanks to the non-porous HDPE shell and 100-foot filtration system.
The complete target table
| Parameter | Target range | What to add if low | What to add if high |
|---|---|---|---|
| Total alkalinity | 80–120 ppm | Sodium bicarbonate | Sodium bisulphate (small doses) |
| pH | 7.2–7.8 | pH increaser | pH decreaser |
| Calcium hardness | 150–250 ppm | Calcium chloride | Dilute with fresh water |
| Free chlorine | 3–5 ppm | Granular dichlor | Allow to dissipate; retest |
After the initial balance
The initial balance after a fresh fill is the most involved session. After that, routine maintenance is far lighter: test weekly, adjust only what the test strip shows is off, and add sanitizer on a regular schedule. On an Eco Spa with its non-porous shell and generous filtration, that routine is measured in minutes per month, not hours.
For a broader look at the ongoing maintenance routine — not just the initial balance — see the beginner's maintenance guide. For a deep dive specifically on alkalinity and why it matters, see the alkalinity guide.