How Do I Get Rid Of Scum In My Hot Tub?


There is nothing better than enjoying a cool summer night than preparing your hot tub and relaxing in it in your backyard. The warm water and the bubbling jets make for one of the most relaxing experiences that you can get right in your backyard! However, you wake up the next morning to drain your hot tub but notice something dirty on the hot tub jet lining: scum lines! It can be a pretty distressing thing to notice since just last night you had used the hot tub but didn’t notice it then.

So how do I get rid of scum in my hot tub? If you are worried about cleaning them but don’t really know the right way to test and clean them effectively. Don’t worry! I have got you covered in that department and here I will teach you the simple ways you can not only get rid of the scum but also make sure that they return less frequently!

Key Takeaways

  • Scum is the unwanted residue that stays in the water and becomes visible when too much of it accumulates in the hot tub water.
  • It is important to know which type of scum you are dealing with so that you can use the effective prevention method to get rid of them.
  • There are many things that might cause scum to form on your hot tub, from your own body to the quality of water and filtration system of your hot tub.
  • If you want to make sure that scum does not return to your hot tub, there are 7 things that you need to do like regular cleaning and testing the quality of water.

Hot Tub Scum and Its Types

Hot tub scum and its types

The simplest way to define scum is the layer of dirt that forms on top of the water due to impurities in the water. In hot tubs, this scum rises up due to the jets in the hot tub constantly stirring the water and keeping it warm.

These scum form and not just affect the water surface but also the lining of your hot tub, filtration system, and jets too! That means once you see scum forming, it could possibly mean that your whole hot tub has scum lurking around the corners.

I will go in-depth about how to get rid of the specific scum on your hot tub in a different section. But for now, let’s give the most basic explanation of what causes the different types of scum to form.

  • Brown scum: oxidation of impurities with chlorine
  • Green scum: high copper and magnesium levels
  • Blue-green scum: a combination of metal and impurities in the water

While it might not be scum per se, there is one other thing that you need to worry about in your hot tub. White scales might form on your water due to too much calcium in the water and it needs a different type of cleaning that needs its own article to fully understand it.

Getting Rid of Scum from Your Hot Tub for Each Scum Type

Getting rid of scum from your hot tub for each scum type

We have seen both what are scums and their types. We have also discussed the different reasons that can cause the different types of scum. All of that build-up was so that you can fully understand scum so that you can effectively get rid of them! So here are the ways that you will be getting rid of scum from your hot tub once and for all!

Brown scum prevention methods

Probably the most easiest scum to get rid of. Brown scum is caused by the oxidation of impurities with chlorine. This means that the pH level of your hot tub water was out of order and caused the perfect conditions to be available for oxidation.

So all you need to do is make sure you test your water’s pH level with test stripes and then add the proper amount of chlorine granules or a pH decrease to balance it. You need your water to be around 7.2 to 7.6 pH level. Too low or too high and you can be sure that is the reason why brown scum is forming!

Green scum prevention methods

Since green scum is caused by trace amounts of a bit too much copper and magnesium in the water that is used to fill up the hot tub, it can be tricky to get rid of a scum like this. That is why the best prevention method for this would be to use an in-line water filter for your hose to fill up the hot tub. The filter can make sure that the metals responsible for green scum are not in excess.

Another thing that you can do for green scum is use a metal sequester like the Pool Mate 1-2550 Metal Out Swimming Pool Mineral Remover. It can help make sure to remove the metal from the water and prevent staining your hot tub shell with green scum!

Blue-green scum prevention methods

Probably the trickiest scum to get rid of because blue-green scum is a combination of different reasons! From body residue, oil, metal, and chlorine, all of them can contribute to this sea-green scum.

That is why you need to do a bit of everything for it! I will talk about some of the prevention methods in-depth in the next section but know that a combination of some or all of these can be the only way you get rid of this type of scum. Here is what you might need to end up doing:

  • Shocking your hot tub
  • Scrubbing your hot tub with oil-absorbing sponges
  • Using a fine-mesh net to clean the surface
  • Draining and cleaning your hot tub
  • Cleaning or replacing filters
  • Using biofilm cleaners and spa treatments

So you can see how difficult it might be to get rid of blue-green scum from your hot tub! The best advice I can give for this type of scum is just to do an overall cleaning of your hot tub. In my experience, that has been the most effective way to get rid of it without wasting time on trial-and-error figuring out which one is causing it.

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What Causes Scum to Form: Finding out the 6 Major Reasons

What causes scum to form finding out the 6 major reasons

Now that we have a basic idea about what scums are, it is time to take a deeper dive into what causes the formation of scum in your hot tub water.

1. Bodily residue and dead skin cells

Our body sheds millions of dead cells every day and secretes sweat and oil from the pores of the skin. When you get into the water, these will get washed in with the water. Over time, a lot of this will gather and form the scum that you might start seeing in your hot tub water.

2. Personal body products

Imagine you are using body lotion, moisturizer, deodorant, and maybe even makeup on yourself. Now imagine doing all of that and then getting into your hot tub. Where does all that product go? That’s right, right into the hot tub water it goes! All these personal body products get washed into the water and then eventually become scum. While the filtration system makes sure to keep your hot tub water clean, over time it can accumulate to form the scum!

3. Metals in the water

The blame can’t be placed completely on you because there are others that can cause scum to form in your hot tub. Out of all of them, the most major cause for concern is the water that you are using. Even the most filtered water will have trace amounts of metals such as iron, copper, and magnesium. Eventually, they will build up to cause green scum to form on your hot tub!

4. Unbalanced spa water chemistry

Along with the metals in the water, another thing that is a cause for concern is the overall water chemistry. You might know that you need to add chlorine or bromine granules to your hot tub water to prevent bacteria formation. However, the metal in your hot tub can react with the chlorine (if you add too much of it) and cause reactions to form blue-green scum on your water! Unbalanced water chemistry is a combination of both you and the water condition.

5. Moldy hot tub

Now if you add too little chlorine to your hot tub water or let’s say that you haven’t used your hot tub in a while, the hot tub will become moldy. Now add water to that, and you have the perfect recipe for the formation of algae and mildew on your hot tub water, which will eventually become green scum on your hot tub along with your body residue!

6. Old and unclean filters

Hidden from our eyes, the filters in a hot tub are working overtime to make sure that your hot tub water remains as clean as possible. It makes sure that your hot tub water is crystal clear and running smoothly without contaminations. But they can only work for so long before becoming old and worn out, where the filters start becoming more and more ineffective because the filters get dirty over time. When the filtration system fails, the formation of scum starts to become more and more frequent.

All of this might seem a bit nasty but it is important to understand why causes them so that you know exactly how to get rid of scum from your hot tub.

Preventing Scum Formation: 7 Things You Need to Do

Preventing scum formation 7 things you need to do

Sure, knowing how to clean your hot tub is great and all. But what if I were to tell you that there is a way so that you can make sure that the scum does not return and absorbs properly (or at least prevent it from coming up so frequently)? I would call that music to my ears! So here are some of the things that I always do before getting in the hot tub:

1. Showering before entering

If you have been to a public pool, you know it’s a common courtesy to shower before diving into the pool. The same thing applies to hot tubs too! You can get rid of most of the dead skin cells and oil from your body before hopping in your hot tub and that makes sure that impurities appear less often on your hot tub.

2. Testing with test stripes

Unbalanced water for your hot tub can mean that scum appears often. But with test stripes to measure pH level or overall water chemistry can help ensure that the water is safe to hop in and you can jump in without any worry for your health either! I would say this is something you can always do so do it before you hop in your hot tub.

3. Using oil-absorbing sponges

Floating oil-absorbing sponges on top of the hot tub water can be really helpful in preventing scum! The sponge will absorb the oil and other smaller impurities by soaking it in and then you easily get rid of the film on top! The great thing about these sponges is that they will float on your hot tub so you can leave them overnight after using the hot tub and then remove them once the morning comes.

4. Shocking your hot tub

While you might be tempted to shock using electricity, that is not what I meant! Shocking your hot tub means doing a purge of the water by adding an excess of chlorine to the water to help oxidize it. This will help get rid of any bacteria or algae hidden in the hot tub by killing it, meaning it is less likely for green scum to form. If you use your hot tub very regularly, then I advise doing a shock of your hot tub every week or every other week.

5. Draining and cleaning your hot tub

There is nothing better than doing a deep clean of your hot tub. Draining the water, and then scrubbing the inner shell of the hot tub can help clear out any impurities that stick to the hot tub. Along with that, you can add new water to the hot tub so you are getting rid of the impurities from the old one. Draining your hot tub might take about an hour or so another hour to completely scrub it down and another hour to fill it back up! But luckily, you have to only do this every 3 months or so if you are regularly using your hot tub.

6. Cleaning and replacing filters

While draining the hot tub is effective, it won’t be effective if the filters are not working properly. This might be due to unclean or worn-out filters in your hot tub that might contaminate new water that you added all over again! That is why it is also important to clean your filters. Use a spray nozzle every week and soak it in warm water and chemical cleaner to help extend the life of the filter!

7. Using biofilm cleaners and spa treatments

Biofilm cleaners and spa treatments are great ways to clean the hot tub from within. It is a chore to open up the hot tub and then clean the whole piping line water intake and the jets as well. So enter biofilm cleaners and spa treatments! You will just have to add it to a running hot tub and let the chemicals work their magic from within. Do this once every month or so to ensure that your hot tub is cleaned from within.

I believe that doing these things will help make sure that the appearance of scum and scum lines is considerably reduced and quite possibly prevent them from appearing altogether!


1. What kills bacteria in hot tubs?

Oxidizing agents like chlorine and bromine can help kill the bacteria in hot tubs. They are also known as the best water sanitizers but you should make sure that the level of chlorine in your water is about 1 to 3 ppm (parts per million).

2. Can I use vinegar to clean my hot tub?

If you don’t have a regular spa treatment, a vinegar solution can be a good way to clean your hot tub. It contains no harmful chemicals and is just as effective as spa cleaners.

3. Why does my hot tub have so much scum?

There could be a whole host of reasons this is the case. Too much residue from your body, the presence of too many trace metals, not cleaning the hot tub often enough, and old filters are just some of the many reasons that your hot tub might have so much scum.

Final Thoughts

Scum is the bane of any hot tub owner. Believe me, I know all about it. That is why getting to know your hot tub’s worst enemy is the first of many steps in battling it. So I hope that you understand all about scum and how you can get rid of it from your hot tub regardless of the type of scum that is present. And remember to do things I have mentioned before and after using the hot tub to make sure that you don’t see the scum appear all that often. So soak in your hot tub stress-free and scum-free!

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I am Donald M. Beyer and I am backyard enthusiasts. I am a homeowner who has been doing DIY projects in and out of my house for many years. From simple backyard lunches to making an old-school pizza oven in my own backyard, I have a lot of experience in turning my backyard into my and my family’s personal playground.

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