When you notice white flakes in your hot tub’s water, it’s almost always one of two things:
- Biofilm
- Calcium scale
Biofilm occurs when your hot tub’s sanitizer (chlorine or bromine) drops too low, resulting in bacteria build-up in your pipes. When dealing with biofilm, the white flakes are often accompanied by an unpleasant and unusual odour, discoloured, oily bubbles, and slimy-feeling water. You’ll also likely have noticed an increased use of chemicals.
Calcium scale build-up is the result of hard water. Just as your kettle gets white flakes around its heating element, so does your hot tub. Calcium scale usually builds up in the hot tubs plumbing, and especially the heater, which eventually detaches and floats around in the water.
How to know if white flakes are biofilm or calcium
Follow these 3 simple steps to determine if you’re dealing with biofilm or calcium scale.
- Fill a cup with water (including some flakes) from your hot tub (around 250 ml).
- Add roughly ½ teaspoon of bleach to the cup and stir.
- Wait 30 minutes.
If, after 30 minutes, the white flakes have dissolved, you likely have biofilm, and if not, it’s likely calcium scale build-up.
Preventing biofilm flakes
Read our article on biofilm to learn more about its removal and prevention.
Preventing calcium scale flakes
Preventing calcium scale is much simpler than dealing with biofilm. Using a stain and scale controller like Jacuzzi Stain & Scale helps prevent calcium build up, and is an important part of protecting your spas components from hard water.
You can remove most or all calcium flakes with a drain and fill. Be sure to use a plumbing cleaner and blow out your lines. If you don't have a wet/dry vacuum you can wrap a rag around the end of a garden hose and push water through your filter pipe for 5 minutes.
Causes of calcium scale
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hard water
Use a multi-stage pre-filter when re-filling your spa. If you have a water softener, partially refill your hot tub with soft water - don't add too much soft water to avoid damage.
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high pH
When pH levels are high it can cause calcium to form from the water. For the best results, keep your pH between 7.2-7.5
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high alkalinity
When alkalinity is high, pH levels also rise which can cause calcium to form from the water. For the best results, keep your alkalinity between 80-120
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high stabilizer
High stabilizer levels can elevate the pH in the water can make balancing water very difficult; both can lead to scale formation. For the best results, keep your stabilizer below 50. Always change your water if it's above 100.
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high total dissolved solids (TDS)
When total dissolved solids (TDS) are high, calcium flakes are more likely to form from the water. Although test strips can't measure TDS, you can buy a TDS meter on Amazon for under $30. For the best results, keep your TDS should be between 1000-2000ppm. The only way to reduce TDS is to drain and refill your spa. We recommend doing this 3-4 times per year.
