How to Remove and Prevent Hot Tub Stains

Hot tub stains come in many types and colors like green, brown, yellow, blue, and even black. While most of these stains appear due to dirty spa water or dirty hot tub shells, some other stains appear for entirely different reasons.

So even if your hot tub is well maintained, you may still notice some pesky stains on the shells of the hot tub. So what exactly causes hot tub stains and how can you remove stains from your hot tub? Let’s find out.

 Most of the time, stains are a result of poor maintenance. There are a lot of other reasons why you might have stains in your hot tub. The reason doesn't matter, what matters is to know how to remove hot tub stains.

What Causes Hot Tub Stains?

There are different causes of stains on your hot tub shell. Here are some of the most common of them.

Dirty Hot Tub Water

This is the most common reason you may notice stains on the shell of your hot tub. If the water in the hot tub has been there for too long or you haven’t drained your hot tub in a while, the water will get dirty.

The dirty water can cause stains on the shell of the hot tub. Most times, hot tub stains that result from dirty spa water are usually brown and on rare occasions, blue-green or black. When the water in the hot tub is dirty, the part of the shell where the waterline forms will start to have brown stains.

If the stain is left there over time, it will accumulate, get dry, and turn black. Though the waterline is usually where you notice most of the stain, dirty spa water will also cause stains on other parts of the shell such as the base of the shell and the walls.

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Scum Build-up

Another reason for dirty hot tub shells is scum build-up. Scum refers to all the foreign contaminants that get into your hot tub water. Contaminants like body care products, hair oils, perfumes, food residue, waste, soda, and the likes cause a build-up of scum inside your hot tub water.

This scum build-up will also cause stains on the shell of the hot tub. Stains that result from scum build-up are usually brown, yellow, and blue-green. These stains usually produce offensive smells too and they can stain more than just the shell of the hot tub.


When the water in the hot tub has a high level of iron like magnesium, calcium, zinc, and the likes, there is bound to be rust. When you add sanitizers like chlorine and bromine to water that has a high level of iron, the iron will react harshly to the sanitizers and oxidize or rust.

The result of this reaction will produce green or brownish-green colors on the surface of the water. This will start to cause scale build-up on the shell of the hot tub. The scales can be green, yellow, and even blue-green.

Too Many Sanitizers

Yes, too many sanitizers can cause stains on your hot tub shell. When you add too many sanitizers to the hot tub water repeatedly, the water will become more acidic and this can cause discoloration or stains on the shell of the hot tub.

If you have too many sanitizers then that will cause stains in your hot tub. Make sure to add the right amount of chlorine and bromine.

When the water is too acidic, it can also damage the shell of the hot tub by corroding it or gradually eating into the shell. Too many sanitizers in hot tub water can cause brown, red, and even yellow stains on the hot tub.

Other causes of hot tub stains include too many bathers in the water, a chlorine build-up, damaged filters, dirty water sources, and the likes. Luckily, most of these stains can be removed with a bit of effort and dedication. So, let’s check out how to remove hot tub stains.

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How to Remove Hot Tub Stains

Removing hot tub stains is a fairly easy process but it can be time-consuming depending on the type of stain you are working with.

Test the Water

The first thing to do is to test the water. As stated earlier, hot tub stains are caused by many reasons. So you need to test the water to know what is causing the hot tub stain, especially if you suspect the stain isn’t caused by dirt. You will need a digital testing kit or a metal testing strip to test the water.

Now, it's time to learn how to remove hot tub stains. The first thing you want to do is to test the water chemistry balance. If you have too much chlorine or bromine you need to fix that.

Test for the iron levels in the water first. If the iron level is high, then the cause of the stain in your hot tub is hard water. You should also test for chlorine levels in the water to be sure the stain isn’t caused by acidic water that may also be corroding the shell of the hot tubs. The next step in cleaning the stains on your hot tub will depend on the result of the water test.

Add the Needed Chemical to the Water

After testing the water, you need to add chemicals to the water. But, the chemicals you will add depends on the result of your water test. If the test showed that there is too much iron or copper in the water, then you need to add a metal remover to the water to reduce the iron level.

If the test showed you have much chlorine in the water or the water is too acidic, then you need to reduce the chlorine level in the water. A common remedy to reduce the chlorine level in water is to add sodium thiosulfate to the water. If you don’t have this available, you can just turn on the heater and remove the hot tub cover so the water is heated and the chlorine is evaporated with the water vapor.

If the test shows you neither have too much chlorine or iron in the water, then the stains are caused primarily by filth and scum. This means you need to shock the hot tub by adding a high dose of sanitizers to the water. The sanitizers like chlorine and bromine will break down the filth and kill the bacteria in the water.

After adding the chemicals, wait for a few hours to let them work before going ahead with the task.

Clean the Plumbing Lines

After adding the needed chemicals, you should clean the lines of your hot tub by adding a line flush to the water. The line flush should be added in the right quantity and should be allowed to circulate for a few minutes in the hot tub.

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Drain the Hot Tub

If you added the needed chemicals and you still have stains in your hot tub then it’s time to drain it. Turn off the hot tub jets using the control panel.

Then turn off the hot tub and switch off the GFCI breaker on the wall. After doing these, locate the drain valve at the base of your hot tub and drain the water. Ensure to drain the water away from your living space.

Wash the Hot Tub

This is another step that is determined by the result of your water test. Ensure to use products that are designed for cleaning the type of stain you are dealing with. As an expert tip, do not use detergent or bleach to clean your hot tub.

Different hot tub cleaning products can be used on the hot tub instead. Detergent and bleach might be too harsh on the shell of the hot tub. If you just use them, ensure they are properly diluted.

Using the hot tub cleaner you got, wash the hot tub. You can use a rag, soft sponge, or a soft brush to wash the hot tub. Ensure to wash all the stains off the shell. This may require some effort on your part because some of the stains would have solidified over time.

Clean the Filters

Remove the hot tub filters and rinse them with water or with a filter cleaner depending on how dirty they are. Ensure the filters are well rinsed and dry. If the filters are damaged, replace them.

Rinse the Hot Tub

Use clean water to rinse the hot tub. You can add cold water to the hot tub, turn on the hot tub and turn on the jets so the water can be circulated inside the plumbing lines too.

You should also check the stained areas of your hot tub to know if they are clean. If the stains are still there, try using alcohol or a stronger solvent to remove the stain. Then rinse the tub again and let it dry.

Refill the Hot Tub

When the hot tub and all its components are fully dry, return the components in their positions. Then refill the hot tub with clean water. Use a hose filter while refilling the hot tub to limit the level of iron and other debris that get into the hot tub.

If you can, stay away from well water while refilling the hot tub. After refilling the hot tub, add the required sanitizers to purify the water. Then test the water after a while to be sure the water chemistry is balanced. If all is right, you should vacate the hot tub for about 24 hours before using it again.

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Last Resort

If you have tried all the steps above and the hot tub is still stained, you should call a cleaning company or a hot tub repair shop to help you out or make recommendations on how to get rid of the stain.

Now you know how to remove hot tub stains but prevention is better than cure. So how can you prevent hot tub stains? Let’s find out.

How to Prevent Hot Tub Stains

The best way to prevent hot tub stains is to keep the water chemistry balanced. If the water chemistry is balanced, you will hardly notice any stain in the water. Let’s see other ways of keeping stains out of your hot tub.

Clean the Hot Tub Regularly

A clean hot tub is a pain-free hot tub. Try cleaning your hot tub shells regularly. This depends on how much you use the hot tub.

Drain the Hot Tub

You should also drain the hot tub once in three months. If the hot tub is used by many bathers, try draining it once in two months.

Add the Right Amount of Chemicals

Either you are adding sanitizers, metal remover, or any other type of chemical to the hot tub water, you should follow the manufacturer’s instructions and add them correctly.

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Always Check the Filters

The filters in your hot tub trap a lot of dirt so they can get clogged. If this happens, scum and grime will float freely in your water and this can cause hot tub stains. So check the filters regularly to be sure they aren’t clogged and are working fine.

Limit the Contaminants You Add to the Water

You shouldn’t eat or drink in the hot tub because food and drink residue can fall into the water and accumulate to form scum. This can very much stain your hot tub.

You should also shower before using the hot tub. This will prevent a buildup of hair and skin care products, body oils, and the likes from staining the hot tub.

So there you have it. You can check out other posts on this website for more hot tub tips. Have a nice day.

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