SpaChoice Alkalinity Increaser for Hot Tub

The Verdict

If your hot tub water tests low for total alkalinity (below 80 ppm), you’re fighting a losing battle with pH bounce, burning eyes, and scale on the heater. The SpaChoice Alkalinity Increaser is a targeted fix that most users report resolves this in a single treatment.

What you actually get

The 2.5 lb bucket is straightforward: granular sodium bicarbonate, a clear label with dosing instructions, and a 1-ounce plastic scoop tucked inside. That scoop matters more than you’d think. Most alkalinity products make you guess ounces or use a kitchen spoon; here, one level scoop per 500 gallons raises alkalinity by roughly 10 ppm. For a typical 300-400 gallon spa, that’s about two scoops to move from 60 to 100 ppm. The bucket itself is sturdy plastic with a screw-off lid, though it lacks a gasket — more on that below.

How it performs in real use

What stands out in the feedback is how quickly it dissolves. Sodium bicarbonate can sit on the water surface in clumps if you’re careless. SpaChoice granules are fine enough that several buyers report dumping the full dose in and seeing it clear within minutes. One reviewer noted: “I added two scoops, ran the jets for five minutes, and my alkalinity went from 50 to 90. No cloudiness at all.” That matches the general pattern: most people see a 20-40 ppm jump within 4-6 hours, and pH stabilizes overnight.

It also plays well with other chemicals. Since it’s pure bicarbonate, it won’t interact negatively with chlorine, bromine, or shock treatments. A few users mentioned using it weekly as maintenance to prevent pH crash, which is a valid strategy if your source water is soft.

What buyers consistently praise

The 4.7-star average across 235 ratings reflects three recurring themes. First, predictability — the dosing chart is accurate, and the scoop makes repeatability easy. Second, value relative to spa store prices. One verified buyer put it plainly: “My local pool store wanted $18 for the same thing. This is half the price and works identically.” Third, the effect on water comfort — multiple reviewers with sensitive skin and eyes reported that fixing alkalinity eliminated irritation without needing to change sanitizer.

Where it falls short

The lack of a moisture barrier on the bucket is the most common complaint. If you store it in a humid basement or an outdoor shed, the powder can absorb moisture and harden into chunks. It’s still usable — just crush it before adding — but it’s an annoyance. Also, at roughly $12-15 per 2.5 lb bucket, it’s pricier per ounce than buying plain baking soda from a grocery store. That’s the honest math: you’re paying for convenience and correct particle size, not magic chemistry. If you’re on a tight budget and already have a kitchen scale, generic sodium bicarbonate works fine.

Who should buy this

• New spa owners who inherited a murky water problem and need a straightforward fix without reading a chemistry textbook.
• Anyone with soft water (below 60 ppm alkalinity) who’s tired of chasing pH with pH Down every other day.
• Renters or seasonal users who want a small bucket that won’t go stale before they use it up.

Skip it if you’re a pool professional managing a large commercial spa — you’ll want a 10 lb or 25 lb bag from a bulk supplier instead.

Frequently asked questions

How often should I add alkalinity increaser? Check alkalinity weekly. If it drops below 80 ppm, add one scoop per 500 gallons, wait 6 hours, and retest. Most users re-dose every 2-4 weeks depending on bather load and fill water.

Can I use this with bromine or salt systems? Yes. It’s pH-neutral bicarbonate and doesn’t interfere with any sanitizer type. Salt systems actually benefit from stable alkalinity because it reduces scale on the salt cell.

Does it raise pH too? Slightly, temporarily. Alkalinity and pH move together, so if your pH is already high (above 7.6), aerate the water for a few hours after adding to let excess CO2 off-gas.

The verdict

The SpaChoice Alkalinity Increaser is a solid, no-surprises product that does exactly what it claims. It’s not the cheapest option per pound, but the accurate scoop, fast dissolution, and consistent results justify the premium for most home spa owners.

Buy it if you want a reliable, easy-to-dose fix for low alkalinity that won’t cloud your water or mess with your sanitizer.

Skip it if you’re comfortable measuring generic baking soda and want to save a few dollars per treatment.

Rating: 4.6/5 — A dependable performer that solves one of the most common hot tub headaches, held back slightly by packaging that doesn’t fully protect against humidity.

Where to Buy

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Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.