What causes white flakes in a hot tub and how to get rid of it

white calcium scale flakes in a hot tub

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.

  1. Fill a cup with water (including some flakes) from your hot tub (around 250 ml).
  2. Add roughly ½ teaspoon of bleach to the cup and stir.
  3. 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.

Jacuzzi Stain and Scale 500 ml - Hot Tub Store
Jacuzzi Stain and Scale 500 ml
from $17.95 $50.85
Protect your hot tub or spa from unsightly stains, scale formation, hard water, and rust with Jacuzzi Stain & Scale Control. This powerful formula keeps your shell and equipment looking pristine, ensuring a long-lasting and enjoyable spa experience. Prevents stains, scale, and rust formation on hot tub surfaces Prevents damage from hard water Prolongs the lifespan of your spa equipment Maintains the visual appeal of your hot tub or spa Features: Effective stain and scale control formula Protects against hard water, minerals, and rust Easy to use and apply Size: 500 ml Directions: Add 1 capful of Jacuzzi Stain and Scale Control to your spa weekly When changing the spa water, add 2 capfuls for thorough protection   Click here for Safety Data Sheet (SDS)


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.

Jacuzzi Whirlpool Rinse - Hot Tub Store
Jacuzzi Whirlpool Rinse
Effectively decreases and removes harmful residue from your spa's internal plumbing system with Jacuzzi Brand Whirlpool Rinse. Add Jacuzzi Whirlpool Rinse to your hot tub before draining. Size: 500 ml   Click here for Safety Data Sheet (SDS)
Ahh-Some Hot Tub Cleaner (2oz) - Hot Tub Store
Ahh-Some Hot Tub Cleaner (2oz)
Ahh-Some Plumbing & Jet Cleaner is a unique and environmentally friendly gel formula that removes biofilm - oils, lotions, cosmetics and more.  User-Friendly Formula Gently Scrubs Inside Your Plumbing & Jets Non-Hazmat Safe for ALL Plumbing & Shell Surfaces Non-Corrosive & Non-Acidic Septic Safe Formula Won't Etch or Disintegrate Components Ahh-Some Hot Tub/Jetted Bath Plumbing & Jet Cleaner is a unique and environmentally friendly gel formula that, when used as directed, removes the build-up of bio-fouling inorganics, oils, lotions, cosmetics, exfoliated skin and other contaminants " from the plumbing (including hot tub's jets) and shell of typical hot tubs and jetted bathtubs. This exclusive formulation will keep your water clean longer for less cost to maintain. Remove stubborn residue like soap scum with Ahh-Some Cleaner Fast! Size: 2oz 


Causes of calcium scale

  • 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.

  • 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

  • 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

  • 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.

  • 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.

Fast FREE Shipping

on orders above $49*

Huge Inventory

on popular hot tub products

Great Customer Service

call or chat with our dedicated team
Visa Mastercard Shop Pay American Express Apple Pay Google Pay