Before we go into looking into the causes of white mold in our hot tubs, how to treat it and how to prevent it from recurring, we must first learn how to identify it. Lucky for us, spa white mold is pretty easy to identify. White mold usually looks like calcium or soap flakes floating around in your spa and because of that, it’s commonly mistaken for a calcium problem. Since spas are typically made from fibreglass, it’s very unlikely that it is a calcium hardness problem.

To be absolutely sure, take a sample of the white flakes along with a glass of spa water. Add in about 1ml of liquid bleach or chlorine and swirl it around. If the flakes are still there, then it’s a calcium problem, but 99 times out of a hundred, the flakes will dissolve and this is a good indication that you have a white mold problem.

Causes of Spa White Mold

As the name implies, white mold is a fungus. They usually thrive in dark spaces like your spas pipes and plumbing. While it doesn’t seem like it, there is usually over 100 feet of piping inside of your hot tub! Plenty of room white mold to lurk and grow in! The combination of tight dark spaces and warm water is the perfect breeding ground for white mold!

White mold is the result of biofilm which is basically a stew of bacteria, dead skin cells, cosmetic products, and natural body oil. Even if you take regular care of your hot tub surfaces with frequent cleaning, there’s still a chance for biofilm to develop, and in turn cause white mold in your hot tub.

Spa White Mold Treatment

While there may be short term solutions to white mold like shocking the spa, this is usually a symptom of something that needs more thorough attention. This is why we recommend a thorough decontamination of your spa.

Super Chlorinate for 72 hours

Raise your spa’s chlorine levels to 20ppm or more for at least 72 hours. Check the levels every 24 hours to see that they’re maintained. Make sure that all water passages are open, diverter valves midway so that all valves, features, waterfalls, jets, and every single pipe is saturated with the super chlorinated water. A missed spot can make all of your work for nothing since biofilm and white mold can spread really fast.

Don’t forget your spa drains

One area that’s commonly neglected is your spa drains since it’s usually a one way street. Don’t forget to drain a bit of the super chlorinated water into the spa drains whenever you check the chlorine levels to ensure that no biofilm is lurking there.

Cleanse the pipes with some pipe cleaning chemicals

Although the super chlorinated water will definitely kill off any mold and bacteria lurking, it won’t melt away any of the debris and slime associated with them. A good dose of Lo-Chlor Pipe Klenz should take care of any debris and slime left in your pipes.

Turn on the jets to flush out any debris in your pipes

Observe the jets to see if any more white flakes come out. The pipe cleaning chemicals should have loosened them already so don’t be surprised to see some white mold still being expelled from your spa jets.

Fully drain your spa

Drain out all of the water from your spa to ensure that nothing gets left behind, refill the spa then observe the jets to see if any more white flakes come out. This should all run clear by now, but if not, drain it again and repeat the process.

Chemically Clean or Replace your spa filters

Rinsing off your spa filters will not be enough if you have already developed a white mold problem. If you have a fairly new spa filter then soaking them in some specially formulated filter cleaning solution should do the trick. If you have an older spa filter cartridge that’s starting to show its age then it would be a better idea to replace the spa filter cartridge element entirely.

Don’t forget to rebalance your spa water

Once you’ve eliminated the white mold from your spa, don’t forget to balance the spa water and add some sanitiser to ensure that it doesn’t come back.

Spa White Mold Prevention

After going through all of that, the trouble of trying to prevent white spa mold will not seem to be a lot of work! Here are the steps you have to take to make sure that the mold doesn’t come back to your spa.

  • Check and balance your spa water on a weekly basis - Even if you don’t use your spa or hot tub, ensure that all of the chemical levels, especially your sanitiser, is on point at least once a week. This in itself is actually more than enough to prevent white mold from taking a hold in your pool.
  • Run your spa pumps a few minutes each day - If you have a timer for your spa then this should be pretty easy to set. White mold thrives in stagnant water. Good thing it only takes a few minutes to fully circulate all of the water in your spa.
  • Rinse off before going into the spa - This is another step you can take to ensure that you don’t introduce oils into your spa too much which may contribute to the formation of biofilm and white mold. With the low water volume of your spa, even the body oils and cosmetics from one or two people can be enough to contribute to the formation of biofilm, and in turn, white mold!
  • Refill your spa immediately after draining - If for some reason you drain your spa, refill it immediately! Allowing it to dry out can lead to the growth of white mold. If you’re leaving your spa drained for extended periods of time, be sure to sanitise it thoroughly before refilling it with water.
  • Check your source hoses - if you refill your spa from a garden hose or something similar, check it for mold before refilling your pool. A contaminated hose can easily transfer white mold into your spa if you’re not careful.
  • Periodically clean your spa pipes - A dose of Lo-Chlor Pipe Klenz every few months should protect you from biofilm becoming a problem. Not only does this prevent white mold, but this makes balancing your spa chemical levels much easier since your sanitiser demand won’t be as high.

SEE ALSO: Getting Rid of Swimming Pool Foam


It’s much easier to prevent white mold than treat it! But once it’s set in, you have no choice but to go through the entire thing. White mold isn’t only an eyesore but it can actually clog up your spa jets, pumps, filters, and other parts! If that isn’t enough then some people will also have reactions to mold and this can cause health issues as well.

Starting over? Consider switching over to a Chlorine-Free Spa with the Lo-Chlor AquaSpa System! Read more about this revolutionary chemical pack here where we take a look at having a chlorine-free spa system.

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