Hot tub startup chemicals are a short list: test strips or a reagent kit, alkalinity increaser, pH up and down, calcium hardness increaser, a sanitizer, an oxidizer shock, and stain and scale control if your water carries metals. Order matters more than brand. Fill through the filter area, heat the water, fix alkalinity first, then calcium and pH, and only then build sanitizer, one product at a time with a test between each.
We sell hot tubs, not chemicals, test kits or filters. Buy those from a pool and spa retailer, and bring your tub’s water volume and owner’s manual. Your manual and the product labels outrank any general guide, including this one.
New hot tub chemicals: what to buy before delivery
- Test strips or a reagent kit. Caldera’s Paradise owner’s manual uses strips for startup; American Spas calls a reagent kit more accurate.
- Alkalinity increaser and pH up and down. Caldera names sodium hydrogen carbonate to raise both and sodium bisulfate to lower them.
- Calcium hardness increaser, if your tap water tests soft.
- Sanitizer and shock. American Spas specifies granulated chlorine, not liquid; Caldera superchlorinates with sodium dichlor at startup. Still choosing a system? See salt water vs chlorine hot tub.
- Stain and scale control. Caldera warns iron and copper can stain the shell.
The Canadian Spa Toronto SE manual pictures a starter kit (chlorine granules, Foam Free, pH up, pH down, test strips), but our listings do not mention one, so plan to buy your own.
First fill: filling and powering up
- Check the equipment bay. Caldera says to confirm the pump and heater unions are hand tight before the first fill.
- Fill through the filter well. Caldera says to remove the filter and fill through the filter compartment with a prefilter on your garden hose; the Toronto SE quick start also fills through the filter housing.
- Use cold tap water, not softened or hot. Caldera warns hot water can trip the high limit and softened water may damage equipment; American Spas says soft water can cause foaming.
- Power on only when full. Caldera warns that powering an empty spa damages components. Wiring belongs to a licensed electrician and local code.
- Let it heat. Caldera waits until the water passes 90 F before adjusting chemicals. Canadian Spa Company says a 240V tub takes 4 to 6 hours to reach temperature.
Hot tub startup chemicals in order: hot tub water balance on day one
Canadian Spa Company’s start up guide says to balance alkalinity before pH, and pH before sanitizer, circulating 30 minutes after each addition and retesting; it allows about 4 hours for the first balance. Caldera explains why alkalinity comes first: when it is off, pH is hard to adjust and sanitizer works poorly. Caldera adjusts calcium after alkalinity and before pH, while the Toronto SE guide does not address calcium at startup. A sequence that respects both:
- Test the fresh water, including metals if your kit can.
- Add stain and metal control if needed, per its label.
- Adjust total alkalinity. Circulate 30 minutes, retest.
- Adjust calcium hardness if your manual gives a range. Retest.
- Fine tune pH. Retest.
- Shock and establish sanitizer.
| Startup target | Caldera Paradise | Canadian Spa Toronto SE | American Spas 2026 |
|---|---|---|---|
| Total alkalinity | 40 to 120 ppm | 80 to 150 ppm | 80 to 120 ppm |
| pH | 7.2 to 7.8 | 7.2 to 7.6 | 7.2 to 7.6 |
| Calcium hardness | 50 to 150 ppm | Not listed | 150 to 200 ppm |
| Start up sanitizer | Superchlorinate, then hold 3 to 5 ppm chlorine | 15 g chlorine granules per 1,000 L | Granulated chlorine, or 2 oz sodium bromide for bromine |
The ranges differ, which is why your own manual comes first.
Shock and sanitizer: finishing the first fill
Caldera says chemicals go into or in front of the filter compartment while a jet pump runs at least ten minutes. After superchlorinating, it tests: 3 to 5 ppm chlorine means move on; lower means circulate and retest. On a Toronto SE, 15 g per 1,000 L works out to roughly 17 g for its listed 1,110 L. Weigh it, and check the label on your product, since strengths vary.
Leave the cover off while the tub vents. Caldera says at least 20 minutes after a shock, warning trapped gas can discolor the cover; American Spas runs jets on high with the cover open for 30 minutes after sanitizer. Canadian Spa Company’s warranty excludes damage from adding chemicals with the cover on. Ongoing levels and weekly shock are in our hot tub maintenance schedule.
When is the water ready to use?
Caldera says the spa is ready when the water has circulated and chlorine holds between 3 and 5 ppm (or bromine 1 to 2 ppm), after a final recheck of alkalinity and pH. High sanitizer levels irritate eyes, lungs and skin, so wait for the reading to settle into range before anyone gets in.
Startup checklist
| Step | Do | Before moving on |
|---|---|---|
| 1. Fill | Cold tap water through a hose prefilter in the filter well | Level per manual, filter reinstalled |
| 2. Power and heat | Breaker on, purge air, cover on | Strong jets, warm water |
| 3. Metals | Stain and scale control if needed | 30 minutes circulating |
| 4. Alkalinity | Adjust to range | Retest |
| 5. Calcium, then pH | One at a time | Retest after each |
| 6. Shock and sanitizer | Dose by volume, cover open | Sanitizer in range |
| 7. Final test | Recheck everything | Ready to soak |
Common first fill mistakes
- Adding chemicals together. Never mix products, in the tub or a bucket.
- Going too fast. Caldera says each step depends on the one before it.
- Using pool trichlor. American Spas says it damages the spa and voids the warranty; Canadian Spa Company excludes trichlor and calcium hypochlorite damage.
- Chlorine on top of biguanide. Caldera warns against it.
- Overdosing. Caldera says measure exactly and never use more.
Follow every label, wear the protection it calls for, and work with good ventilation. Caldera says to store chemicals cool, dry, ventilated and away from children, never in the equipment compartment.
Water volume on the tubs we carry
Doses scale with volume. Listed capacities from Canadian Spa Company, American Spas and Cal Spas tubs (prices at the time of writing):
| Hot tub | Water capacity | Listed water care | Price |
|---|---|---|---|
| Canadian Spa Muskoka 5-Person | 900 L | Ozone, 50 sq ft Glacier filter | $6,000 |
| Canadian Spa Cambridge 6-Person | 1,000 L | Ozone, 50 sq ft Glacier filter | $7,999.99 |
| Canadian Spa Toronto SE 6-Person | 1,110 L | Ozone, Glacier filters | $12,749 |
| American Spas 6-Person 40-Jet Lounger | 425 gal | HydroClear ozonator, 50 sq ft filter | $7,300 |
| Cal Spas Balboa PZ-516L | 125 gal | 50 sq ft Bio-Clean filter | $6,700 |
| Cal Spas Pacifica Plus PPZ-743L | 425 gal | 50 sq ft Bio-Clean filter | $9,200 |
A 125 gallon tub needs less than a third of the dose of a 425 gallon tub, so a one size “capful” rule does not work.
Frequently asked questions
What hot tub startup chemicals do I need for a first fill?
Test strips or a kit, alkalinity increaser, pH up and down, calcium increaser if your water is soft, sanitizer, shock, and stain and scale control if your water has metals. Buy them from a pool and spa retailer.
Should I balance alkalinity or pH first?
Alkalinity. Caldera and Canadian Spa Company both put it first because it controls how easily pH moves.
How long until I can soak?
Plan on a day: hours of heating, then about 4 hours of balancing per Canadian Spa Company, with 30 minutes of circulation after each addition.
Do I repeat this when I refill?
Yes, the same sequence applies after every drain. After winter antifreeze, follow the flush steps in how to winterize a hot tub, and clean the cartridge using our hot tub filter guide.
Sources: Caldera Paradise owner’s manual, Canadian Spa Toronto SE manual, Canadian Spa Company start up guide, American Spas owner’s manual.
Questions before you buy? Call 866-777-2590, Monday to Friday, 9AM to 6PM PST. Orders of $999 or more ship free by freight; smaller orders ship for a $200 flat rate. See our return and refund policy.
