To keep your hot tub water sanitized, you’ll need to add enough chlorine to keep your chlorine levels at around 3 parts per million (PPM). But it’s easy to overdose your hot tub with too much chlorine. Knowing how much chlorine to add depends on the size of your spa and your starting chlorine levels.
As a general rule for weekly maintenance, add 1/2 teaspoon (.17 oz) of chlorine granules for every 100 gallons of water. That means for a 500-gallon hot tub, you’ll need to add about 2 1/2 teaspoons (.5 oz) of chlorine granules each week.
If your chlorine level is at 0 PPM or you’re battling an issue like cloudy water, you’ll need a larger dose. Add 1 teaspoon (.34 oz) of chlorine for every 100 gallons of water to superchlorinate your hot tub water.
Note: These calculations are based on a concentrated formula of chlorine granules (almost 99% sodium dichlor chlorine).
By the way, if you’ve never added chemicals to your hot tub before or you’re feeling totally overwhelmed by water chemistry, check out our Hot Tub Course.
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Check Out The Course HereHow Much Chlorine Do You Need in a Hot Tub
Your hot tub chlorine levels should be around 3 per million (PPM). Anything above 5 PPM will cause irritation and corrode your hot tub surfaces and anything below 1 PPM will lead to unsanitary water.
Most people add chlorine granules (a.k.a. sodium dichlor chlorine) to sanitize their hot tub water, but others sanitize with slow-dissolving tablets or liquid chlorine. Regardless of what you use, plan on testing your water at least once a week and after adding chlorine to find the right dosages.
Chlorine Granules
This fast-dissolving chlorine is added directly to your hot tub water. For maintenance, add 1/2 teaspoon (1/6 ounce) of chlorine granules for every 100 gallons of water.
This granular, stabilized chlorine is fast-acting and quick-dissolving. You can add it directly to your hot tub water. Because this product contains CYA (stabilizer), it's best used in outdoor hot tubs that are exposed to UV rays.
Chlorine Tablets
Chlorine tablets are slow-dissolving pucks that are added to a chlorinator or floating dispenser. It’s a simple, hands-off way to keep your water consistently sanitized. One or two 1-inch chlorine tablets are usually enough to sanitize 500 gallons of water. Just make sure that your dispenser (floater or chlorinator) is releasing the correct amount of chlorine. It’s very easy to overchlorinate the water if your setting is too high.
One-inch chlorine tablets are a better option for smaller pools and hot tubs (compared to three-inch tablets). Be sure to buy a smaller chlorine dispenser and set the dosing rate appropriately.
Liquid Chlorine
Like granules, this concentrated form of chlorine is added directly to your hot tub water. You don’t need that much to keep your hot tub sanitized, so be sure to measure out the amounts before adding it. One to two ounces of liquid chlorine is enough to sanitize 500 gallons of hot tub water. But you’ll need to test after dosing since each formula has a different concentration of chlorine.
How to Add Chlorine Granules to Your Hot Tub
Before you start adding any chlorine granules, you need to know how many gallons your hot tub holds. Your hot tub’s volume or water capacity is found in your owner’s manual or by looking up the model of your hot tub online.
You’ll also need the right measuring tools. Because you’ll be dealing in such small quantities, it’s important to have a kitchen measuring cup, tablespoon, and teaspoon for your hot tub. As a reference:
- 1/4 cup = 2 ounces
- 1/8 cup = 1 ounce
- Tablespoon = 1/2 ounce
- Teaspoon = 1/6 or 0.17 ounce
Finally, you’ll need the right chlorine granules. Look for a superconcentrated formula (almost 99% sodium dichlor chlorine) that also comes with an oxidizing agent. That will help break up any organic compounds in the water and help activate existing chlorine in the water.
This granular, stabilized chlorine is fast-acting and quick-dissolving. You can add it directly to your hot tub water. Because this product contains CYA (stabilizer), it's best used in outdoor hot tubs that are exposed to UV rays.
Once you have your chlorine granules and you’ve measured out how much chlorine you need, here’s how to it to your water:
- Keep your hot tub jets on low with the air off. You want your water to circulate, but too much air can affect your chlorine and pH. Turn the jets low and the air valves off. Make sure your water is heated to at least 85 degrees Fahrenheit (30 Celcius) to help your chemicals dissolve.
- Test and balance your pH and alkalinity first. These levels affect your chlorine’s ability to sanitize the water, so make sure they’re in range before adding chlorine. If you need more help balancing your chemistry, check out our guide on Hot Tub Chemicals for Beginners.
- Add chlorine directly to your hot tub water. Measure out your chlorine first, then add it directly to the surface of your hot tub water.
- Wait at least 20 minutes before retesting the water or adding other chemicals. Keep your hot tub jets running and your air valves off to help your chemicals evenly and quickly disperse.
- Keep your cover off. You’ll want your hot tub cover removed so the chlorine can “off-gas.”
Remember, you can always add more chlorine later. So start with a conservative dose, let the chlorine dissolve, then retest your water. You’ll get a better understanding of how much chlorine to add to your spa overtime.
Frequently Asked Questions about Hot Tub Chlorine
Need more help adding chlorine? Here are some common questions and answers.
How Much Chlorine Do I Put in a 300-Gallon Hot Tub?
For a 300-gallon hot tub, add 1 1/2 teaspoon of chlorine granules once per week. If you need to superchlorinate your water because your chlorine is at 0 PPM or you have cloudy water, use around 3 teaspoons. You can always add more, so test before and after adding a conservative dose.
How Much Chlorine Should I Add to a Hot Tub Each Week?
For a weekly maintenance dose, add 1/2 teaspoon of chlorine granules for every 100 gallons of water. That means 1 1/2 teaspoons for a 300-gallon hot tub and 3 teaspoons for a 600-gallon hot tub.
Can I Put Too Much Chlorine in a Hot Tub?
Yes, it’s easy to add too much chlorine to a hot tub. So if you’re unsure how much you need to add, start slowly with a conservative dose and retest your water after 20 minutes. If your chlorine levels get too high, you can lower your chlorine by letting some of the water evaporate and refilling it with fresh water. Here’s our guide on How to Lower Hot Tub Chlorine.
Should I Put the Jets On When Adding Chlorine?
When adding chemicals like chlorine, turn your hot tub jets on low and turn your air valves off. Having active movement in the water will help the chemicals dissolve faster. But you don’t want too much air, which can oxidize your chemicals and increase your pH. Turning off the air valves will prevent that from happening.
How Soon Can I Go in a Hot Tub After Adding Chlorine?
After adding chlorine, wait at least 20 minutes before using your hot tub. Make sure to retest the water before using, especially if you’ve superchlorinated the water. Your chlorine should be around 3 PPM before you use the hot tub.
Need More Hot Tub Maintenance Help?
- Download our free Hot Tub Cheat Sheet. It’s a free, easy-to-use guide to help you keep your hot tub water balanced and sanitized.
- Subscribe to our Swim University YouTube Channel. We publish free video tutorials throughout the year.
- Check out our Hot Tub Care Course. You’ll get step-by-step videos and a downloadable guide with everything you need to know about hot tub maintenance.
