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Clear Up Cloudy Hot Tub Water in Less Than 2 Hours

By Matt Giovanisci | Updated: September 11, 2023

Cloudy hot tub water is caused by these common pool issues: contaminants, metal or minerals in your water, low chlorine or bromine, high pH or alkalinity, biofilm inside the plumbing, or a dirty filter. Here’s a step-by-step guide on how to fix these common issues, and how to clear up a cloudy hot tub fast using a clarifier or hot tub line flush.

You can watch the quick video tutorial below. Or keep reading for the complete cloudy hot tub water troubleshooting guide.

What Causes Cloudy Spa Water?

1. Contaminants like Debris or Algae

Dead leaves, grass clippings, and all the other natural matter that blows around your backyard can land in your hot tub during use or when left uncovered.

As your sanitizer (like chlorine or bromine) tries to break down contaminants, it’s quickly used up. This means the more contaminants in your water, the harder the sanitizer has to work. And it may not be able to keep up with killing bacteria and other contaminants, causing murky or cloudy water.

Cloudy water can also occur after killing algae with chlorine shock. That’s because the dead algae floating around in your water and circulation system can cause murky water until they’re filtered out.

2. Metal or Minerals in Your Water

When you fill your hot tub, you probably hook a hose up to an outdoor spigot or indoor tap and let it run until your spa is full. Do you know whether your household water source has high concentrations of metal? If you’re not using a hose filter when you fill your hot tub, metals and minerals in your hard water could be contributing to cloudiness.

Over the long term, filling your spa with water that contains high levels of metal can alter your water chemistry, and can stain your spa’s shell and components. High calcium levels from hard water can also cause cloudiness. Your hot tub’s calcium hardness levels should be between 175 to 250 ppm. And if your levels are too high, you’ll see scale build-up and cloudy water.

3. Low Chlorine or Bromine

Has your spa recently had a high bather load? If you’ve had more guests using your spa than usual, you may not be adding enough sanitizer to keep up with the amount of foreign matter (read: body oils, shampoo residue, and other icky stuff humans slough off everywhere they go) being introduced to the water.

When you notice cloudiness after an increase in hot tub use, insufficient sanitizer levels might be the culprit. When you don’t have enough chlorine or bromine to effectively sanitize your spa water, bacteria, algae, sunscreen, and even—yes, we’re sorry to say—fecal matter is able to linger in the water causing a cloudy appearance. Your fellow bathers could even pass illnesses to each other and you.

4. High pH or alkalinity

Like most things in life, achieving balanced hot tub chemistry isn’t impossible, but maintaining balanced water all the time takes work and dedication.

If you’ve let your water care routine slip, your cloudy spa water could be the result. Not all chemistry problems necessarily cause cloudiness, though. So what should you look for?

5. Biofilm Inside the Plumbing

Contaminants like sweat, body oils, and bacteria can build up over time in your hot tub lines. It starts to form a protective layer called biofilm that makes it resistant to your normal chemicals.
So every time water passes through your plumbing, that gross buildup circulates back into your water. The only way to remove it is with a hot tub line flush cleaner. So every 3 to 4 months, plan to drain your hot tub and purge your pipes.

6. Dirty Filter

Dirty water is sucked into your filtration system so the filter can get rid of larger particles your sanitizing chemicals would take too long to break down. But if your filter is dirty or not properly installed, those particles wind up suspended in your spa water, slowly decomposing, leaving your water cloudy and dirty.

How to Clear Up a Cloudy Hot Tub

Once you’ve established the cause of your cloudy spa water, you have a few options to clear it up. Using a hot tub clarifier will clear up your water immediately, but it only fixes the symptom, not the cause of the cloudiness. The problem will return if you don’t take steps to eradicate the source of it.

1. Clean The Filter

At the first sign of cloudy spa water, check your filter. Pull it out, give it a deep cleaning or replace it Whether it’s gunked up with sunscreen, choked by flakes of scale, or full of algae, if your filter can’t do its job well, it will show up in your water.

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2. Run The Filter

Your spa water needs to go through filtration for at least one hour, twice a day. Whether you run it manually or program automatic filter cycles, be sure you’re doing so often enough to clear contaminants so your sanitizer can work.

Remember, more hot tub use requires more filtering and more sanitizer.

3. Balance Your Chemicals

If you determined a specific chemical needs to be adjusted in your spa due to cloudy hot tub water, fix that first. Once you’ve done that, test your water to make sure all your chemical levels are still where they need to be. If they’re not, adjust accordingly.

To make troubleshooting chemical levels even easier, make—and stick to—a hot tub maintenance schedule that includes water care.

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4. Shock Your Water

Algae blooms and all sorts of contaminants can be stopped in their tracks with a good, ol’ shock. In fact, when you follow recommended water care for your hot tub, you’ll be adding spa shock weekly (or even more often) depending on the capacity of your hot tub and how much use it gets.

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5. Start Using a Metal Sequestrant

Unlike the other solutions, which are part of maintaining an overall healthy spa, you won’t need to add a sequestrant unless you’ve determined that your water source contains metals, and that they’re the cause of your cloudy hot tub water.

If metal is indeed the culprit, you can add a metal sequestrant which will bind with the metal, preventing it from oxidizing and discoloring your spa and water. You’ll need to add it when refill your hot tub (using filtered water), as well as adding a weekly maintenance dose.

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09/19/2023 05:24 am GMT

6. Flush Your Hot Tub Lines

To address a biofilm problem, and just as a general best practice, flush your spa lines whenever you change your water. Before draining your hot tub, add a line flush product to your cloudy spa water. Allow it to circulate for at least 30 minutes, but check the product you choose for the recommended circulation time just to be sure.

You’ll most likely see some foaming while the flush circulates. This is normal. It’s just all the biofilm and other gunk coming out of the plumbing. This is why you use line flush before you drain the hot tub. Otherwise, you’ll be draining and refilling twice.

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If you’re experiencing cloudiness that just won’t go away despite your best efforts, it’s time to break out the big guns and drain and clean your hot tub.

Start with a line flush product and a new filter, drain your spa, thoroughly clean the shell, then fill it up using a hose filter.

Remember to add a metal sequestrant if necessary, then shock and balance the fresh water, so you’re starting up with a clean slate.

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How to Prevent Cloudy Hot Tub Water

Follow some simple best practices to keep cloudy spa water at bay:

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Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.

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Save Time and Money with Our FREE Hot Tub Cheat Sheet
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