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How to Remove and Prevent White Flakes in a Hot Tub

By Matt Giovanisci | Updated: October 22, 2015

Have you noticed little white flakes in your hot tub water? Maybe after a soak when the water is still you see some collecting by the drain? I know, they look gross.

But what exactly are they and how do you get rid of them? Let’s take a look at the most likely causes of these white flakes and what you need to do to get rid of them once and for all.

What Are Those Pesky White Flakes?

Once you spot those white flakes floating in the water or hovering by your drain, you need to act fast before the problem gets even worse. Of course, the problem is, what are those things anyway?

There are two possible causes for white flakes in your hot tub, and knowing which one you are dealing with will help you treat your hot tub properly.

The two possible causes are:

Calcium Scale

Calcium scale is the most likely culprit behind those little white flakes you are seeing in the water. They occur when there is too much calcium in your water, otherwise known as hard water. Over time, the calcium accumulates and begins to form white flakes in your spa.

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Biofilm Growth

I am going to be brutally honest here. Your hot tub and the area around it is a warm and moist environment, making it the perfect breeding ground for mold if you aren’t careful. Of course, if you take care of your hot tub, this more than likely won’t be an issue.

However, if your hot tub has sat for an extended period of time unused or you do not clean it properly, this type of mold could grow inside it resulting in those little floaty flakes.

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Test What Type of Flakes You Have

It is very easy to determine what type of white flakes you are dealing with in your hot tub. To find out, collect some of the flakes and spa water in an 8-ounce cup or bowl. Once you have it collected, place 20 drops of bleach or liquid chlorine into the water. Gently stir the water and sanitizer solution and then wait for 30 minutes.

If the flakes are still in the water after 30 minutes, then they are most likely calcium scale deposits. If the white flakes have disappeared, then they are more than likely a biofilm buildup from mold.

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Remove the White Flakes and Prevent Their Return

Once you get your hot tub back into shape, you don’t want to have to deal with this problem ever again because, well, who would want to soak in a hot tub with white flakes floating around in it? I certainly wouldn’t.

What preventative measures you need to take depend on the source of your white flake fiasco.

Calcium Deposits

Getting rid of excess calcium all comes down to your water balance. Hard water is a problem in many areas, meaning that this problem can be quite common for hot tub owners. In order to get rid of this problem once and for all, you will need to follow a couple of steps.

  1. Balance your water properly – First, make sure that the pH alkalinity is properly balanced. Calcium scale will begin to form if your pH is too high so bring those levels down to reduce the hardness of the water.
  2. Try a scale preventer – Hot tub manufacturers and suppliers all make different scale preventers that you can add to your water on a regular basis to reduce the buildup in calcium. This can be especially important if the water in your area is particularly hard. These treatments often have to be added on a regular basis such as every week. While the treatments vary, a good rule of thumb is to add 4 ounces per 100 gallons of water when you fill it and then every week at 2 ounces per 100 gallons if you have a high mineral content in your water. If the mineral content is low, try adding 2 ounces per 100 gallons when you first fill your tub and then 1 ounce every week per 100 gallons.

White Water Mold

This is probably the easiest to prevent, as it all comes down to how you clean it. White water mold occurs most often in hot tubs that haven’t been used for a while or hot tubs that have not been cleaned in some time.

To prevent this excess biofilm, all you need to do is give your hot tub a proper cleaning both inside and out with full water and filter changes.

As long as you regularly take care of your hot tub by testing and balancing the water and properly cleaning it on a regular basis, your excess biofilm problem should never be an issue again.

Final Thoughts

Remember, it all comes down to hot tub care. If you own a hot tub, it is important that you regularly test the water and clean the hot tub to make sure that your water is clear, clean and safe to use. If you don’t, you could end up seeing these nasty little flakes appear in your water, and nobody wants that!

Happy Soaking!

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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