Hot Tub Chlorine Dose Calculator

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FAQ: Balancing Your Hot Tub Chlorine

What is free chlorine in a hot tub?

It’s the amount of active sanitizer in your water that’s actually killing germs. In most spas, you want free chlorine in roughly the 1–3 ppm range (some manufacturers allow up to around 5 ppm). Below that, the water can go cloudy or unsafe; far above that, it can be irritating to skin, eyes, and swimsuits.

How do I use the calculator to figure out how much chlorine to add?

Enter your hot tub’s size in gallons, choose whether you’re doing a routine dose, a post-party boost, or a shock, and then plug in your current test-strip reading. The calculator estimates a teaspoon amount of dichlor granules based on your volume and target ppm, then scales the dose up or down so you don’t overshoot your chlorine level.

How often should I test my hot tub’s chlorine?

At a minimum, test before you soak and at least a few times per week. If the tub is getting heavy use (parties, kids in and out, etc.), it’s smart to test daily. The more people use the tub, the faster chlorine gets used up, so frequent testing keeps you from drifting into “too low” or “way too high” territory.

What’s the difference between a maintenance dose and a shock dose?

A maintenance dose is a small amount you add regularly to keep chlorine in the normal soaking range. A shock dose is a much larger one-time hit meant to burn off contaminants and quickly raise chlorine when the water is cloudy or smelly. After shocking, you normally leave the cover off, run the jets, and wait for chlorine to drop back into a safe range before soaking.

What should I do if I add too much chlorine?

If you overshoot, don’t soak. Leave the cover open, run the jets to help chlorine off-gas, and retest every so often until the level drops back to a safe range (around 1–3 ppm, or what your manufacturer recommends). For extreme over-dosing, you can partially drain and refill with fresh water to bring the level down faster.

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