Why Is My Hot Tub Water Cloudy?

Feet poking out of a steaming hot tub.

Hot tub conditions and bacteria

Unlike swimming pools, spas have a low volume of water that’s kept at high temperatures. The average home hot tub holds around 1820L of water. Combine this relatively low volume with the high temperatures that make a hot tub so relaxing and you create an environment for dangerous contaminants like legionella – the bacteria responsible for Legionnaire’s disease.

That’s why hot tub maintenance is so important, as a bacteria build-up in your tub could make it potentially dangerous to bathe in.

Here are some of the main causes of cloudy hot tub water, what they mean, and how you can reverse them to get clean and clear water back.

Causes of cloudy hot tub water


Debris and natural matter such as dead leaves, grass, and pollen are one potential cause of cloudy hot tub water. They can fall into your hot tub if it doesn’t have a proper cover, especially during autumn months.

This could result in your spa’s circulation system and filter clogging up, preventing them from working. Then, as the debris breaks down, the water in the tub will become cloudy, and unfortunately, a potential health risk.

Getting rid of these contaminants is fairly easy using regular hot tub cleaning chemicals but your spa sanitiser will most likely get used up quickly so make sure you have some in reserve.


Algae floating in a body of water.

Algae are aquatic plants that form in a hot tub when the water’s pH levels are imbalanced, or when sanitising products like chlorine and bromine are in short supply. Sunlight makes algae flourish, so leaving your hot tub uncovered for a long time can exacerbate the problem.

Prevent algae from forming with regular hot tub water maintenance and make sure to keep your hot tub covered whenever it’s not in use. Keeping your hot tub covered also benefits your bank balance as it’ll keep the spa warm and save you from the electric costs involved in constantly reheating it.

Water source

Household water supplies often contain traces of metal, and while this doesn’t cause major problems with everyday tasks like cooking and laundry, it can prove to be a problem when it comes to your hot tub.

For instance, water containing trace metals can drastically change a tub’s water chemistry and stain its surfaces. With this in mind, it’s crucial to always use a hose filter when filling your tub as this will remove any contaminants from your hard water, which are otherwise likely to cause cloudy water.


If cloudy water is identifiable after a sudden increase in hot tub use, it’s worth upping the volume of the sanitiser you use. Of course, in periods where hot tub use naturally increases (e.g. summer), you should prepare to use more still.

If you overlook sanitiser or don’t apply enough to keep up with demand, your spa may become a quickly contaminated, giving the water a cloudy appearance and making it unsuitable for bathing in.

Poor water chemistry

If you neglect your water care routine, it’s highly likely that your hot tub water will become cloudy. However, not all chemistry problems cause water cloudiness, so what else should you look out for?

High pH

If your water’s pH is too high (7.6>), it may result in two problems:

  1. Scale formation
  2. Ineffective sanitising

If these problems occur, deal with them by using a pH decreaser. Simply dissolve the recommended amount in warm water and then add the solution to the spa water (as close to the inlet valve as possible to ensure it disperses evenly).

High alkalinity

If your spa’s water exceeds 150ppm, a scale will form; eventually leading to a pH imbalance. Unfortunately, when this happens, all of the contributors to cloudy water combine to make your spa hazardous to bathe in. The solution? An alkalinity decreaser, designed to stabilise pH levels, as well as destroy all organic contaminants, including algae.

High calcium hardness

Ideally, your spa’s calcium hardness will be between 175 to 250 ppm. If your levels are too high, however, scale build-up will occur, as well as drastic alterations in your water’s chemistry and appearance (i.e. cloudy).

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