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The Ultimate Hot Tub Water Treatment Guide

Owning a hot tub can work wonders for your quality of life. Being able to soak in warm, soothing waters a few steps from your back door opens up a world of wellness benefits—from relaxing massages to improved sleep to more opportunities for family time. In order to enjoy these benefits, choose a water care system that ensures your water is always hot and ready.

To help you make the right choice, and to answer any questions you may have about spa water care maintenance after installation, we’ve compiled a comprehensive hot tub water treatment guide. It is possible to minimize the time you spend on cleaning and maintenance so you can spend more time enjoying your hot tub.


If left untreated, hot tub water will become unsanitary; bacteria and other microorganisms can grow in the water. Minerals can build up as well, eventually harming internal systems or causing unsightly scale or residue to appear on the hot tub’s shell.

Hot tub water care doesn’t have to be difficult, but you do need to have a good understanding of your system and the necessary maintenance schedules to keep the water clean and inviting. Understanding the chemistry of your water before it goes into the spa is as important as the water care option that you choose. Water should be free of metals (iron, copper, and manganese) and low in calcium hardness. Your local dealer can help you test your local tap water before you get started.

You’ll find in this hot tub water treatment guide introductions to the various water care systems and the maintenance involved. Your local dealer can offer even more in-depth knowledge of your model’s water care features and maintenance needs. They can help you determine a schedule for any daily, weekly, monthly, or annual tasks, and they can help you plan for the simplest approach to water care. It’s important for you to understand the ins and outs of your spa so your water will be clean and ready for you to step in at any time.


This guide to hot tub water care covers:

If you run into questions at any point along the way, you can find many answers about water care online, or you can reach out directly to your HotSpring® dealer for personalized attention and advice.


All hot tubs make use of technology and additives to keep the spa water fresh and clean. Without a system to remove contaminants and destroy microorganisms, the water in hot tubs would become much less inviting and potentially harmful. To prevent this, a variety of water treatment systems have been designed and have been proven to work effectively over years of use and happy hot tubbing. Together, with scheduled water testing, maintenance, and draining and refilling, innovative water care systems can sustain crystal clean and comfortable spa water for daily use.

Hot tub water treatment systems work in different ways to achieve adequate sanitization. Depending on the technology, some may require more effort from owners to support the sanitation process; whereas, some are more hands off. Some allow the hot tub water to last much longer before it needs to be changed; some depend on more frequent draining and refills.

Some of the most popular hot tub water treatment systems include salt water chlorine generators, ozone generators, in-line chlorine sanitation, and manual chlorine addition.


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Read our startup guide for tips on how to get set up with our system.

Salt water chlorine generators, such as the FreshWater® Salt System*, are the ultimate in modern hot tub water care. These systems generate chlorine automatically from low levels of salt in your hot tub's water. With this method, the FreshWater® Salt System can keep the water in your hot tub fresh and clean for up to a year of normal use** far longer than other systems can.

With this reliable and largely automatic system, an owner's time and effort is minimized. The FreshWater® Salt System is available on all 2019 Hot Spring® Highlife® Collection and Limelight® Collection spas. As with other water treatment systems, an additional mineral sanitizer such as the FreshWater Mineral Spa Sanitizer continuous silver ion purifier inhibits bacteria, helps maintain a neutral pH for softer, more balanced water when used in conjunction with the FreshWater® Salt System.


Combine the FreshWater Salt System with the revolutionary FreshWater Smart Monitoring System for the most comprehensive water care available. The Smart Monitoring System automatically tests your water every hour and provides clear instructions when adjustments are needed for clean water.

Learn More about FreshWater IQ****


Hot tubs with in-line chlorine sanitizing systems, such as the FROG® @ease® In-Line Sanitizing System, dispense chlorine and important minerals into the hot tub's water automatically. This maintains a constant residual amount of chlorine, which prevents bacterial growth and eliminates contaminants. The minerals inhibit bacteria growth and soften the feel of the water.

These systems remove the need to continually test and adjust multiple chemical levels of the hot tub's water on a daily and weekly basis. This technology can also keep the spa water clean with up to 75% less chlorine***** than manual chlorine systems require.


Hot tubs with ozone systems, such as the FreshWater® Ozone System, clean the water constantly, using a combination of ozone and FreshWater ag+. The ozone destroys contaminants.

With ozone systems, owners also need to add a dose of chlorine to the hot tub on a weekly basis. These systems require less chlorine overall than hot tubs that don't use ozone; this reduction in chlorine may also reduce odors and irritation. Ozone systems can be used in combination with in-line chlorine systems but should not be used in combination with salt water chlorine generators.


Without an automatic water care system of some type, the owner needs to manually add chlorine on a regular basis to get the hot tub water ready for use. This requires frequent testing of the amount of chlorine in the water, as well as the water's pH and calcium levels. Because chlorine dissipates quickly in water and needs to be replaced, this type of system requires more chlorine overall to maintain a constant residual amount for sanitation.


When you first install your hot tub, or after you drain and refill it, you'll need to take a few small steps to get your water ready for use. If you're first installing your hot tub, your local hot tub dealer will be able to walk you through the process. They'll also be ready to answer any questions you have when it's time to refill. In addition to consulting with your local dealer, read the owner's manual for your spa for complete details.

If your water care system comes with a separate sheet of start-up instructions—as the FreshWater® Salt System does—you should consult this as well. To determine what sort of treatment your spa water may require, take a sample of your tap water to your local dealer. They'll be able to identify any additional products you'll need to treat your water, such as Vanishing Act® Calcium Remover or On the Go®, a portable water softener used while filling your hot tub. Your local dealer may also recommend using a Clean Screen® Pre-Filter on your hose to filter out unwanted metals, Stain and Scale Control to treat for metals.


Now that your hot tub is warm and ready, the next step is to test the water regularly to ensure that it remains clean and properly balanced. The amount and type of testing you'll need to do will be determined by the type of hot tub water treatment system you have installed. There are four types of test strips used in Hot Spring® hot tubs, each for a separate purpose.

  • FreshWater® 5-WAY Test Strips: Used at varying frequencies in hot tubs that are treated by ozone, in-line chlorine sanitizers, chlorine generators, and manual chlorine addition—5-way test strips help you monitor your chlorine, bromine, pH, alkalinity, and total water hardness. These are the basic test strips used regularly in many hot tubs.
  • FreshWater® MPS Test Strips: Designed to be used in conjunction with the MPS non-chlorine Oxidizer, these strips will detect your MPS, pH, and alkalinity levels.
  • FreshWater® Salt Test Strips: Used exclusively with the FreshWater® Salt System and other salt water systems, these test strips measure the amount of salt in your spa water
  • @ease® Test Strips: Intended for use with the FROG® @ease® In-Line Sanitizing System, these simple single-color test strips measure chlorine, pH, total alkalinity, and calcium hardness of your hot tub's water.
  • Phosphate Test Strips: Test phosphate levels of your spa water from 0 to 2500ppb. Recommended use for FreshWater Salt System

When you test your water, if the levels of each chemical are within the acceptable ranges on your test strips, then there's nothing more for you to do to get ready for a relaxing soak. However, if a test strip returns a reading outside of its acceptable range, you'll need to take a few minutes to correct the imbalance.


Balancing your hot tub's chemical levels is relatively easy and doesn't take a lot of time. Depending on the results shown on your test strip, you'll need to adjust either your chlorine levels or pH/Alkalinity levels or shock your water using an MPS oxidizer. To do so, you'll use concentrated chlorinating granules, pH/Alkalinity Up, or pH/Alkalinity Down. The MPS chlorine-free oxidizer you'll use to shock your spa's water comes either in a basic form or as MPSCENTS®, which helps enhance your hot tub experience with delightful aromas.

Each bottle of hot tub water care products you use will come with its own set of instructions. If you're unsure of how much to add, consult with your local dealer. They will happily talk you through the process.

NEW! For a smarter, simpler, more efficient way to maintain your spa water, consider FreshWater IQ**** , the only in-line self-monitoring system that tells you what it needs to maintain clean, natural-feeling water. Learn more at FreshWater IQ.


The last portion of hot tub water care you'll want to keep in mind is the maintenance of your filtration system. While sanitizers and shock products reduce bacterial growth and destroy small amounts of contamination, larger foreign objects—such as pine needles, pollen, or leaves—must be filtered out.

It's important to rinse hot tub filters with a garden hose once a month to keep them clean. You should also soak them in FreshWater® Salt System Filter Cleaner every time you drain your hot tub. These innovative filters can even be cleaned in the dishwasher without soap on an unheated cycle. Based on need, you can clean your filter with the spray-on, no soak FreshWater® Instant Cleaner Filter as well.


Hot tub water treatment is an essential part of using and enjoying your hot tub. With the right spa treatment system, your water care routine will require only minimal attention and effort. And with water care taken care of, you're free to step into your hot tub and unwind any time.

Hot Spring® Spas has been a leading manufacturer of the highest quality hot tubs and water care systems for decades. To find the perfect hot tub near you, contact your local dealer today.

* The FreshWater® Salt System cannot be used on HotSpring® Spas hot tubs manufactured prior to 2019.

*** Factors such as bather load and water chemistry can impact water life. When the spa is properly maintained, a 3-pack of cartridges with the FreshWater® Salt System will keep water clean and fresh for a full year. Product availability depends on your region Please check with your local dealer.

*** Check for availability in your region.

**** FreshWater IQ is available on 2024 Highlife® Collection and Limelight® Colleciton spas.

***** Compared to the minimum ANSI recommended chlorine level of 2.0 ppm for a hot tub.