Phosphates in Hot Tub: How to Test and Treat

Step into the wonderful world of hot tubs! Picture yourself in a cozy tub of warm water, surrounded by bubbles, while you enjoy a refreshing cold drink. It’s the ultimate way to unwind. But before you get too relaxed, let’s talk about something important: phosphates. These little things can turn your hot tub paradise into a yucky green mess. In this blog post, we’re going to explore the topic of phosphates in hot tubs and teach you how to check for them and deal with them like a pro. So, get ready to become a superhero who fights off phosphates and keeps your hot tub amazing!

Chemical Composition of Phosphates

Phosphates are a type of chemical compound composed of phosphorus, oxygen, and hydrogen atoms. They are found in many forms, including phosphoric acid, orthophosphate, and polyphosphate. The most common form of phosphate found in hot tubs is orthophosphate, which is a single molecule of phosphorus and four molecules of oxygen.

What Causes Phosphates in Hot Tub?

Phosphates in hot tubs primarily result from organic contaminants like body oils, lotions, and detergents, or from source water impurities. These phosphates can lead to algae growth and water quality issues if not properly managed through regular maintenance and water testing.

Sources of Phosphates in Hot Tub Water

Hot tub owners should be aware of the potential sources of phosphates that can negatively impact water quality and lead to various issues.

1. Tap Water Trouble: When you fill your hot tub with regular tap water, there are chemicals in it that stop pipes from rusting. These chemicals, called phosphates, can end up in your hot tub and make the water’s phosphate levels go up.

2. Soapy Situation: The stuff you put on your body like lotions, shampoos, and soaps can have phosphates. When you use these products and then go in the hot tub, those phosphates can get into the water. The same goes for swimsuits washed with soaps that have phosphates.

3. Natural Nuisance: Even leaves, dirt, and other natural things have phosphates. If these things get into your hot tub and stay there, they can add more phosphates to the water.

The Effects of High Phosphates in Hot Tub Water

If the levels of phosphates in hot tub water become too high, it can lead to issues such as the growth of algae and other contaminants, leading to cloudy water, scaling, and corrosion. In such cases, it’s important to reduce phosphate levels to maintain proper water chemistry and ensure the cleanliness and longevity of the hot tub. The most common method for reducing high phosphate levels is to use a specialized product designed specifically for this purpose, which typically contains a chemical called a sequestering agent. Regular monitoring and maintenance of phosphate levels will help keep spa water clean and clear and provide a safe and enjoyable hot tub experience.

How to Test for Phosphates in Hot Tub

Maintaining the right balance of phosphates in your hot tub is crucial to ensure the water is clean and safe for use. Although phosphates occur naturally in many sources of water, they can accumulate over time, resulting in issues such as cloudy water, algae growth, and unpleasant odor. Thus, it’s essential to regularly test the phosphate levels in your hot tub to prevent these problems.

Here are the steps you can follow to test for phosphates in your hot tub:

Step 1: Purchase a phosphate test kit

You can find phosphate test kits at any pool or spa supply store. These kits are easy to use and come with detailed instructions on how to perform the test.

Phosphorus and Phosphate Detection Test Strips, 0-100...
  • No reagents or field kits needed for tests, all you need is one strip and no chemicals
  • Easy to use waterproof color chart printed on every vial along with instrucions
  • Distinct color scale with marks at 0, 30, 75, 150, and 300 PPM Phosphate (and 0, 10, 25, 50, and 100 PPM Phosphorus)
  • Long plastic strips ensure you can keep your fingers away from what is being tested

Step 2: Collect a water sample

Using a clean container, collect a water sample from your hot tub. Make sure to collect the sample from at least 18 inches below the surface of the water.

Step 3: Prepare the test kit

Follow the instructions on the test kit to prepare it for use. Typically, this involves adding a few drops of a reagent to the water sample.

Step 4: Perform the test

Next, add the testing reagent to the water sample as per the instructions, and then swirl the water in the container for several seconds. You should see a color change in the water that indicates the phosphate level in your hot tub.

Step 5: Interpret the results

Refer to the instructions provided with your test kit to determine what the color of the water means. Typically, the kit will have a color chart that you can match the color of your water against.

Step 6: Take corrective action

If the phosphate levels in your hot tub are high, take corrective action to reduce them. One way to do this is to use a phosphate remover product that’s designed for hot tubs. These products work by bonding with the phosphates in the water and making them easier to filter out.

Importance of Maintaining Proper Phosphate Level

First and most importantly, think of phosphate as a kind of food that can make algae and other yucky things grow in your hot tub. This can make the water look cloudy, create slimy stuff, and make your time in the hot tub not so nice. If you want to stop the algae from growing and make your water clear again, you need to make sure there isn’t too much phosphate.

But wait, there’s more! Too much phosphate can mess up the parts of your hot tub, like the filter and the heater. Too much of this stuff can block the filter and make it not work as well. That means your hot tub has to work extra hard and use more energy. It might even make the filter and other parts of the hot tub not last as long, and that means you’ll have to spend money to fix them.

To avoid all these problems, it’s really important to make sure the phosphate level in your hot tub is just right. You can do this by checking the water in your hot tub often using a special kit to measure the phosphate. If the level is too high, you might need to add something to get rid of the extra phosphate, or even change the water in the hot tub.

Phosphates in Hot Tub

How to Remove Phosphates from Hot Tub

1. Phosphate Remover

An effective way to get rid of phosphates from your hot tub is to use a phosphate remover. This product works by bonding with the phosphates in the water, which makes it easier to filter them out. You can easily find phosphate removers in most pool and hot tub stores, and they are simple to use. It is essential to follow the instructions provided with the product to ensure that you add the correct amount to your hot tub.

2. Water Change

Another option is to perform a water change. This involves draining the hot tub and refilling it with fresh water. While this can be a more time-consuming and labor-intensive method, it can be effective for reducing high phosphate levels in your hot tub. After refilling the hot tub, be sure to test the water again and adjust the chemical levels as needed to maintain a healthy and balanced environment for your hot tub.

3. Ozonation

Ozonation is another technique that can be used to remove phosphates from your hot tub. This process involves using an ozone generator to create ozone gas, which is then injected into the water. The ozone gas oxidizes and breaks down the phosphates, making them easier to filter out of the hot tub.

4. Ultraviolet (UV) Sterilization

Phosphates in Hot Tub
Source Credit:

Ultraviolet (UV) sterilization is another option for removing phosphates from your hot tub. This method involves using a UV light to sterilize the water and break down any organic matter, including phosphates. While UV sterilization can be effective for reducing phosphate levels, it is important to note that it is not a complete solution and should be used in conjunction with other methods, such as phosphate removers or water changes.

Take a look at this informative post that features a comprehensive list of highly-rated UV sterilizers for hot tubs.


In the end, properly monitoring phosphate levels in hot tub water is essential. Phosphates are necessary for maintaining a healthy and balanced hot tub environment, but too much can lead to cloudy water, algae growth, and other problems. Proper maintenance requires regular water testing to ensure that phosphates remain within acceptable levels.

3.5/5 - (2 votes)

Leave a Comment