You finally carved out time to close your 2-person inflatable hot tub before the first freeze, and now you’re staring at your bromine supply wondering whether to dump in a handful of tablets, add a scoop of granules, or just skip it and drain. It feels like a small decision, but get it wrong and you’ll open a stinking, stained liner in spring.
The right bromine shutdown dose for a 2-person inflatable hot tub is enough to push your free bromine level to 10-20 ppm before you drain – roughly double the normal maintenance range. For the typical 200-250 gallon tub in this size class, that translates to about 1 to 2 oz of bromine granules (or an equivalent sodium bromide and oxidizer combination), circulated for 30 minutes through the jets before draining. The rest of this article walks through why that range matters, how to hit it reliably, what to do about the plumbing, and the mistakes that cause the most spring headaches.
Why the Closing Dose Is Higher Than Normal Maintenance
During normal use, you target 3-5 ppm of free bromine. That range keeps the water safe while you soak. A winter closing dose is different – it is a one-time sanitizing treatment designed to do two things: knock out any bacteria and biofilm clinging to the shell and jet nozzles before the water drains, and leave enough residual bromine coating the surfaces to suppress anything that tries to grow during months of dark, damp storage.
The 10-20 ppm target gives you a meaningful margin. At 10 ppm, you have a solid kill dose for common bacteria and mold spores. At 20 ppm, you are at the upper end of what is safe for vinyl and PVC liners in short-term contact – and “short-term” here means the 30-60 minutes the water is circulating before you drain, not an ongoing soak. Letting bromine sit above 20 ppm for hours can bleach or stress the liner seams on a soft-shell inflatable, so do not overshoot and walk away.
How Many Gallons Is a 2-Person Inflatable Hot Tub, Really?
Before you measure anything, know your actual water volume. Two-person inflatables vary more than you might expect. The most common models hold between 180 and 300 gallons when filled to the recommended water line. A Lay-Z-Spa or Intex 2-person round typically lands around 210-250 gallons; a compact square model can be as low as 175 gallons. Your owner’s manual has the exact number, and it is worth confirming because a 50-gallon difference changes your dose by roughly 20%.
For the worked example below, the article uses 220 gallons as a representative midpoint for a standard 2-person inflatable.
Step-by-Step: Adding Bromine Before Closing
- Test your starting level. Dip a test strip or use a drop-based kit. If bromine is already above 5 ppm, you still need to bring it up to 10-20 ppm for the closing treatment – just start from a higher baseline.
- Balance the water first. pH should be 7.2-7.6 and total alkalinity 80-120 ppm before you add the closing dose. Bromine is less effective at high pH, and an unbalanced water chemistry can permanently stain a vinyl liner during storage. Adjust pH and alkalinity and wait 15 minutes before moving on.
- Oxidize with a non-chlorine shock. Add 1 oz of potassium monopersulfate (MPS) per 200-250 gallons to oxidize organic waste. Run the jets for 20-30 minutes. This step clears out the bather residue and contaminants that would otherwise eat your bromine dose before it can do its job.
- Add the bromine shutdown dose. For 220 gallons, dissolve 1.5 oz of sodium bromine granules in a bucket of warm water and pour it into the tub with the jets running. If you use a two-part bromine system (sodium bromide plus an oxidizer activator), follow the product label ratio, but target the same 10-20 ppm endpoint. Test after 15 minutes to confirm you are in range.
- Circulate for at least 30 minutes. Keep the jets running so the treated water moves through every nozzle and the plumbing loop. This is the step most people skip, and it is the one that makes the biggest difference for preventing biofilm in the lines.
- Test one final time. Confirm the reading is between 10 and 20 ppm. If you are below 10 ppm, add another 0.5 oz and circulate for 10 more minutes. If you are above 20 ppm, let the jets run longer with the cover off until it drops.
- Drain, rinse, and dry. Drain completely, rinse the shell with clean water, and wipe down every surface before storage. Any standing water in a folded, stored inflatable becomes a mold incubator over winter.
Worked Example: 220-Gallon 2-Person Inflatable
Say your tub holds 220 gallons. Your pre-closing test reads 2 ppm bromine. You need to add enough to reach at least 10 ppm – so you are raising bromine by 8 ppm across 220 gallons. A general rule for bromine granules is that 1 oz raises bromine by roughly 8-10 ppm per 200 gallons. So a single 1 oz dose should land you right around 10-12 ppm, comfortably inside the target range. If your test comes back at 9 ppm, top up with a small additional amount – about 0.25 oz – and retest. That is the full closing dose: one pre-balanced water adjustment, one MPS oxidizer treatment, and one 1 to 1.5 oz bromine granule dose, all circulated for 30 minutes before draining.
If you want a detailed guide on chemical choices for inflatables more broadly, this breakdown of what chemicals are needed for an inflatable hot tub covers the full product category in useful detail.
Tablets vs. Granules for a Closing Dose: Which Works Better?
| Form | Dissolve Speed | Control Over Dose | Best Use |
|---|---|---|---|
| Bromine Tablets (1″ or 1.5″) | Slow (hours to days) | Low – hard to hit a precise ppm quickly | Routine maintenance via floater |
| Bromine Granules | Fast (minutes) | High – easy to measure and dose accurately | Shock doses and closing treatments |
| Sodium Bromide + Oxidizer | Fast (minutes after activation) | High – two-part system with predictable yield | Establishing bromine bank and closing treatments |
Tablets are designed for slow, steady release through a floater – useful for keeping your normal 3-5 ppm week to week, but the wrong tool for a closing dose you need to hit in under an hour. Granules dissolve in minutes and let you control exactly how many ppm you add, which is why they are the right choice here. AquaDoc’s bromine granules are formulated for this kind of fast-dissolve application, and a single 1 lb container will handle several closing cycles on a small inflatable. For a 2-person tub, you genuinely do not need much at all.
What About the Plumbing and Jets?
Inflatable hot tubs have simpler plumbing than hard-shell models – typically a single pump-driven circulation loop feeding the air jets or water jets. That simplicity is actually good news: if you circulate the treated water for 30 minutes before draining, you have covered the plumbing. The bigger risk with inflatables is the pump and filter housing, which can trap water that freezes and cracks plastic components.
After you drain, remove the filter cartridge, rinse it, and store it indoors. Detach the pump unit if your model allows, and let all components air dry completely before you pack them. Bestway’s inflatable winterizing tips are worth a read if your model is a Lay-Z or similar brand, since they include brand-specific pump removal steps. For a broader overview of the full winter closing process – including draining sequence and cover storage – Bud’s Pools covers the safe hot tub shutdown process in clear detail.
One note: if you are on the fence about closing at all and your region only gets light frosts, you may find that keeping a small inflatable running through winter costs less than you expect. The article on winter hot tub use in freezing temperatures breaks down what that actually involves, so you can make an informed call before you drain.
Common Mistakes That Cause Spring Headaches
- Skipping the oxidizer step: Adding bromine to dirty, organics-laden water wastes most of your dose. The bromine reacts with bather waste instead of sanitizing surfaces. Always shock first.
- Not circulating long enough: Pouring bromine in and immediately draining means the jets and pump housing never get treated. Run the jets for a minimum of 30 minutes.
- Using tablets for the closing dose: Tablets left floating in the tub while it drains contribute almost nothing to the closing treatment and can bleach the liner if they sit against it during draining.
- Leaving water in the pump or filter: Even a small amount of standing water in the pump housing can freeze, expand, and crack the casing. Every component needs to be fully drained and air dried.
- Skipping the pH adjustment: Bromine’s effectiveness drops sharply above pH 7.8. If your water is basic going into the closing treatment, you may not get the kill level you think you are adding.
If your tub has had trouble holding a sanitizer reading during the season, that is a sign of an underlying water chemistry problem worth understanding before you close. The post on why a hot tub won’t hold a sanitizer reading explains the most common causes and is worth checking if this has been a recurring issue for you.
Frequently Asked Questions
How much bromine do I add when closing a 2-person inflatable hot tub for winter?
Add enough bromine granules to raise your free bromine level to 10-20 ppm before draining. For a typical 2-person inflatable holding 200-250 gallons, that is approximately 1 to 1.5 oz of bromine granules dissolved in water and added with the jets running. Always test after 15 minutes to confirm you are in the target range before you drain.
What bromine level should a hot tub be at before winterizing?
The target closing residual is 10-20 ppm free bromine – roughly double the normal maintenance level of 3-5 ppm. That elevated level provides a meaningful sanitizing treatment to the shell and plumbing during the final circulation cycle before you drain, without being high enough to damage a vinyl liner on short contact.
Can I use bromine tablets instead of granules to close my inflatable hot tub?
Tablets work for routine maintenance but are the wrong tool for a closing dose. They dissolve too slowly to hit a precise ppm target in time for a same-day drain. Granules or a sodium bromide and oxidizer combination will raise your level within minutes, letting you confirm the dose with a test strip before draining.
Do I need to shock before adding bromine when closing an inflatable hot tub?
Yes, always oxidize first. Use 1 oz of non-chlorine shock (potassium monopersulfate) per 200-250 gallons, run the jets for 20-30 minutes, and then add your bromine closing dose. Skipping this step means organic waste in the water consumes a significant portion of your bromine before it can sanitize the surfaces you actually care about.
Should I drain my inflatable hot tub before or after the closing bromine dose?
Add the bromine dose first, circulate for at least 30 minutes, then drain. Running the treated water through the jets and plumbing loop coats the interior surfaces and helps prevent mold and biofilm from forming during storage. Draining before treating the water defeats most of the purpose of the closing dose.
The Bottom Line
For a 2-person inflatable hot tub, the winter closing bromine dose is about 1 to 1.5 oz of granules targeting 10-20 ppm, oxidizer treatment first, 30 minutes of jet circulation, and then a complete drain and dry. Get those steps right and your liner and plumbing will be clean and ready to refill whenever you open back up in spring.