Swim Spa Chemicals: Gallons, Dose and Schedule

A swim spa is a long, deep tub with a current to swim against. It is filtered and heated like a hot tub, but it holds about as much water as a small pool. Use the gallons your maker lists, dose for those gallons, and follow the maker's chemical levels and schedule.

How many gallons is a swim spa?

Use the capacity in your owner's manual or spec sheet. Examples from one maker's published specs (Hydropool Aquatic collection):

• 14 ft model (14AX, 174 × 93 in outside): 1,900 US gallons.
• 17 ft model (17AX, 210 × 93 in outside): 2,400 US gallons.
• 19 ft dual-temperature model (19DTAX): 1,762 gallons in the swim side and 315 gallons in the separate spa side.

Other makers list similar sizes. Marquis lists its V174S swim spa at 1,600 gallons, for example. Dual-temperature models have two separate bodies of water, so dose each side for its own gallons.

The calculator below works out gallons from inside length, width, and water depth. With the example inside size of 13 × 6.5 ft and 3.5 ft of water, it gives 2,212 gallons (8,375 L), inside the range makers list. It treats the tub as a plain box, though, with no seats, steps, or footwell, so it can still read high. Use it only if you can't find your maker's number, and measure the open swimming area, not the outside of the cabinet.

Pool volume calculator

Inputs

Above-ground model (optional)None: I will enter the sizeIntex Easy Set 6ft x 20in (Happy Crab / Jolly Whale)Intex Easy Set 8ft x 24inIntex Easy Set 10ft x 24inIntex Easy Set 10ft x 30inIntex Easy Set 12ft x 30inIntex Easy Set 15ft x 33inIntex Easy Set 18ft x 48inIntex Metal Frame 8ft x 20inIntex Metal Frame 10ft x 30inIntex Metal Frame 12ft x 30inIntex Prism Frame 12ft x 30inIntex Prism Frame 15ft x 48inIntex Greywood Prism Frame 18ft x 48inIntex Clearview Prism Frame 16ft x 48inIntex Prism Frame 16ft x 8ft x 42inIntex Prism Frame 20ft x 10ft x 48in (oval)Intex Clearview Prism Frame 13ft x 6.5ft x 48inIntex Ultra XTR Frame 14ft x 48inIntex Ultra XTR Frame 16ft x 48inIntex Ultra XTR Frame 18ft x 52inIntex Ultra XTR Frame 20ft x 48inIntex Ultra XTR Frame 24ft x 52inIntex Rectangular Ultra XTR Frame 18ft x 9ft x 52inIntex Rectangular Ultra XTR Frame 24ft x 12ft x 52inIntex Rectangular Ultra XTR Frame 32ft x 16ft x 52inBestway Steel Pro MAX 15ft x 42in (with LED light)Bestway APX 365 22ft x 52inBestway APX 365 24ft x 12ft x 52inBestway APX 365 31ft 4in x 16ft x 52inBestway Fast Set 12ft x 30inBestway Fast Set 6ft x 20inIntex and Bestway models whose capacity we checked on the maker’s site. Picking one fills in its size.

ShapeRectangleRoundOvalKidneyL-shape

Measured inFeetMeters

Lengthft

Widthft

DepthWater depth (shallow and deep end)Above-ground wall height

Shallow end water depthft

Deep end water depthft

Result for example values. Enter your own numbers.

2,212 gal8,375 L

Average depth 3.5 ft.

Chemical amounts for about this size: 2,000 gallon pool dose chart.

Check your water for 2,212 gal: chlorine, pH, and alkalinity doses in order.

For the most accurate number, use your model's stated capacity or calibrate it: add a known amount of salt and measure how much the salt level rises.

Estimates, not guarantees. Always follow the product label. How we calculate

Chlorine amount per ppm for your swim spa

The table below shows how much product raises chlorine by 1 ppm at 1,500 to 5,000 gallons. For example:

• 2,000 gallons: 2.0 fl oz (61 mL) of 12.5% liquid chlorine, 4.1 fl oz (122 mL) of 6% household bleach, or 0.5 oz (14 g) of 56% dichlor.
• 2,500 gallons: 2.6 fl oz of 12.5% liquid chlorine, 5.2 fl oz of 6% bleach, or 0.6 oz of 56% dichlor.

Amount for +1 ppm chlorine in a swim spa

Swim spa size	Pool liquid chlorine 12.5%	Household bleach 6%	Dichlor 56%
1,500 gal	1.5 fl oz45 mL	3.1 fl oz91 mL	0.35 oz10 g
2,000 gal	2.0 fl oz61 mL	4.1 fl oz122 mL	0.5 oz14 g
2,500 gal	2.6 fl oz76 mL	5.2 fl oz152 mL	0.6 oz17 g
3,000 gal	3.1 fl oz91 mL	6.2 fl oz183 mL	0.7 oz20 g
4,000 gal	4.1 fl oz121 mL	8.2 fl oz244 mL	0.95 oz27 g
5,000 gal	5.1 fl oz151 mL	10 fl oz305 mL	1.2 oz34 g

Multiply by how many ppm you need. Use the sanitizer level and products your swim spa maker lists.

Download this data (CSV)

Multiply by the ppm you need to add. For your exact gallons, use the liquid chlorine calculator, or the 2,000-gallon dose chart as a close guide. Our hot tub chlorine calculator stops at 1,500 gallons, so it does not fit most swim spas. Always follow the product label and your swim spa maker's directions.

Levels swim spa makers list

Each maker publishes its own ranges, so check your manual first. As one example, a Master Spas owner's manual for its H2X swim spas (2012 edition) lists:

• Free chlorine: 1–3 ppm, or bromine: 3–5 ppm.
• pH: 7.2–7.8, best at 7.4–7.6.
• Total alkalinity: 80–150 ppm in its startup steps; another page of the same manual calls 80–120 ppm the best range.
• Calcium hardness: 150–250 ppm in the startup steps (180–250 ppm in its quick chart).

The same manual approves only one chlorine product for its swim spas: sodium dichlor. Dichlor adds stabilizer (cyanuric acid, CYA) each time you use it, about 0.9 ppm of CYA per 1 ppm of chlorine (PHTA), so CYA builds up between water changes. The CYA buildup calculator shows how fast. For how each reading affects the others, see the hot tub chemistry chart.

Swim spa vs hot tub chemicals

The product types are the same: chlorine (often dichlor) or bromine, pH and alkalinity adjusters, and shock. The differences are amounts and schedule:

• Volume. A swim spa holds several times the water of a hot tub, so every dose is several times bigger. Never use a hot tub dose chart without scaling it to your gallons.
• Sanitizer type. Pick chlorine or bromine and stay with it, and never mix the two. If you want to switch, ask your swim spa maker how. If you use bromine, see hot tub bromine for how it works.
• Products labeled for spas. Use products whose label covers spas or hot tubs, and follow the label for your gallons.

Weekly routine

1. Test the sanitizer level before each use. The Master Spas manual also lists testing sanitizer, pH, and alkalinity 3 times a week.
2. Adjust alkalinity first, then pH, then sanitizer, following your maker's ranges.
3. Add sanitizer after heavy use, as your maker directs. The Master Spas manual, for example, lists a small dichlor or non-chlorine shock dose after each use and a larger one once a week.
4. Rinse or soak the filters on the maker's schedule. The Master Spas manual says at least once a month.
5. Test calcium hardness and CYA about once a month.

How often to drain and refill

Makers give different intervals, and heavy use shortens them:

• Hydropool recommends draining a swim spa about every 4 months, or once a quarter. It says draining and refilling take a couple of hours, and heating the water back up takes about a day.
• The Master Spas H2X manual lists draining and refilling every 180 days, and notes that the interval may vary with how many people use the spa and how often.

Drain sooner if the water stays cloudy or foamy after shocking, or if CYA or calcium climbs above your maker's range, because only fresh water lowers them. The Master Spas manual suggests a submersible pump, because a swim spa's own drain is slow for that much water. For estimating gallons in smaller tubs, see hot tub gallons.

FAQ

How many gallons does a swim spa hold?

Most models we checked hold about 1,600 to 2,400 gallons. Hydropool lists its 14 ft model at 1,900 gallons and its 17 ft model at 2,400 gallons. Use the number in your own manual for dosing.

How much chlorine do I put in a swim spa?

Enough to reach your maker's range, based on your gallons. At 2,000 gallons, 2.0 fl oz of 12.5% liquid chlorine raises chlorine by 1 ppm. For your exact size, enter your gallons in the liquid chlorine calculator. Always follow the product label.

How often should you change swim spa water?

Follow your maker. Hydropool recommends about every 4 months, and a Master Spas manual lists every 180 days. Drain sooner with heavy use, or when CYA or calcium gets too high.

Can I use hot tub chemicals in a swim spa?

Yes, the same product types work if the label covers spas, but scale the amounts to your swim spa's gallons. Hot tub dose charts are written for a few hundred gallons.

Sources

• Hydropool, Aquatic collection technical specifications (14AX 1,900 gal, 17AX 2,400 gal, 19DTAX 1,762 + 315 gal): hydropoolhottubs.com (PDF)
• Marquis, V174S swim spa (1,600 gallons): marquisspas.com
• Master Spas, 2012 H2X owner's manual (chemical ranges, dichlor, schedule, draining): masterspaparts.com (PDF)
• Hydropool, How to drain a swim spa (every 4 months; time to drain, refill, and heat): hydropoolhottubs.com
• PHTA fact sheet, Dichlor (CYA per ppm of chlorine): phta.org