High phosphates in your hot tub? What you need to know

high phosphates hot tub

The last thing you want to see when you open your hot tub cover for a relaxing soak is green water. But why is your hot tub green?

Minerals, pollen, and low sanitizer levels can all cause green hot tub water. But another culprit can be phosphates.

If you find yourself asking, “What are phosphates?”, we can’t blame you. As a hot tub owner, you are focused on the total alkalinity, pH, and sanitizer levels. But high phosphates can negatively affect your water quality and allow algae and other organisms to grow.

Another reason that you want to avoid high phosphates in your hot tub: It can lead to biofilm.

But what causes high phosphates in hot tubs and how do you lower the level? These tips will help you successfully maintain your spa water and get the most out of your spa.

hot tub benefits
Phosphates are not dangerous on their own. However, high levels can make your sanitizer ineffective and allow bacteria and algae to grow.

Source of high phosphates in hot tubs

Phosphates are a chemical compound made from phosphorus, a natural occurring element and oxygen. Phosphates can also contain hydrogen, calcium, and other chemicals. They can be found in everything from cleaning products, food, and toothpaste.

And, yes, phosphates can be found in your hot tub water. But how do phosphates get in your water?

Sources of phosphates in your hot tub include your source water, rain, natural elements like leaves, body oil, and cosmetic products. But more often than not, the source of the phosphates are residual laundry soap that is on the fabric of the swimsuit or T-shirt that you wear into the spa.

Phosphates and chlorine

Phosphates are a naturally occurring compound. What’s the problem? High phosphates in your hot tub can make your sanitizer (chlorine or bromine) less effective. Chlorine or bromine is essential to keeping your water clean, clear, and safe to use.

But when the phosphates are too high, you can add a high amount of chlorine and it still won’t be able to break down the phosphates. Why? The compound decreases the available free chlorine found in your spa. The amount of chlorine you will need to add will continue to increase.

The best practice is to treat the water for phosphates if your levels are more than 1,000.

hot tub chemicals
You should add chlorine to your hot tub after every use and rinse your filters once a week. If you are struggling with high phosphates, you should rinse your filters more often.

Are hot tub phosphates dangerous?

Phosphates on their own are not harmful. But as a hot tub owner, your concern is how a high level of phosphates will affect your chlorine levels.

Bacteria and algae can thrive when your chlorine levels are too low, making the hot tub unsafe for soaking. When your phosphate levels are high, your chlorine or sanitizer levels could be too low to prevent algae and bacteria growth.

Keep in mind that having a cover on your spa (aka no sunlight) will not prevent algae growth. The water temperature, often between 100 degrees and 104 degrees, is ideal for algae growth.

High phosphates can also lead to biofilm, which leaves a slimy residue on your spa and its components.

How to remove phosphates

Water care and maintenance will be much easier if you are able to lower your phosphate levels.

But how do you remove phosphates from your hot tub water?

The first step is to focus on the filters, the unsung hero of hot tub care. Rinse and clean your filters. It is also beneficial to increase your filter cycles so that they are running for a longer duration.

You can also use a phosphate cleaner, following the manufacturer’s directions. But when the phosphate cleaner is cycling through, it’s important to continue the longer filter cycles and clean your filters more often.

hot tub water problems
What happens when your water isn’t crystal blue? It’s a sign that you might have a problem with algae, minerals, or bacteria. The color of your hot tub water will point to the culprit.

Prevention tips

What is the best way to keep your phosphates in a safe range? Regular water care. It’s important for all hot tub owners to regularly balance chemicals, remove debris like leaves, and avoid algae growth. 

But it’s also about limiting the amount of phosphates you introduce to your water. Laundry soap residue on swimsuits and lotion on your skin are the most likely culprits. To prevent products like those affecting your water, be sure to rinse off before getting in the spa. You should also wash your swimsuits in water only and hang them to dry.

While rinsing off or washing swimsuits separately might feel like an extra step, you’ll appreciate soaking in clean, clear water.

modern spa
A modern patio needs a sleek spa and coordinating steps.

Do you have questions about hot tub care?

Whether you have need more tips or want backyard ideas, our forum and its members offer tips and tricks.

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