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Addressing Hot Tub Scale Build-up During the Winter Season

Addressing hot tub scale in winter

As winter approaches, spa owners often face a common challenge: hot tub scale. This crusty deposit, primarily composed of minerals like calcium and magnesium, can significantly impair hot tub function and reduce its lifespan. Understanding the nature of scale, its causes, and effective management strategies is essential for maintaining a hot tub in top condition during the colder months.

Understanding Scale Build-up

What is Scale?

Scale appears as a hard deposit that often forms on the surfaces of a hot tub, its heater, and internal plumbing. Chemically, it’s mainly calcium carbonate, a residue left behind when hard water evaporates. This substance can vary in color, typically appearing white or grayish, and can feel rough to the touch.

Why Winter Exacerbates Scale Formation

The colder weather of winter can increase scale formation in hot tubs. This happens because of the stark contrast in temperatures between the hot water inside the tub and the cold external environment, leading to increased evaporation rates. As the water evaporates, it leaves behind minerals that contribute to scale build-up.

Causes of Scale Build-up

Hard Water

Hard water, rich in minerals like calcium and magnesium, is the primary culprit behind scale. These minerals are soluble in water but can solidify as temperatures change or when water evaporates, forming scale.

pH and Alkalinity Imbalances

Water chemistry plays a pivotal role in scale formation. A high pH level (above 7.8) can precipitate the minerals out of the water, leading to scale. Similarly, high total alkalinity can stabilize the pH at higher levels, further contributing to the problem.

High Water Temperature

The warm temperatures maintained in hot tubs, particularly during winter for comfort, speed up the mineral precipitation process, leading to quicker scale formation.

Preventive Measures

Regular Water Testing

Frequent testing of hot tub water is vital. Aim to check pH, alkalinity, and hardness levels weekly. The ideal pH range is between 7.2 and 7.8, while the total alkalinity should be maintained between 80 and 120 ppm (parts per million).

Accurate testing helps ensure the maintenance of water balance, essential to avoiding scale formation due to changes in mineral concentration and pH levels in colder months. It allows for timely adjustments to water chemistry, preventing conditions conducive to scale, and helps manage mineral concentration, especially important in regions with hard water. Streamlined testing and digital tracking offered by advanced testing products make winter maintenance more efficient, promoting cost-effectiveness by avoiding overuse of chemicals and protecting hot tub equipment from scale-related damage.

The AquaChek® Select® Connect Kit provides accurate readings, on a connected smart device, of pH, alkalinity, and hardness. As mentioned, these parameters are significant in preventing scale formation. A balanced pH and alkalinity level reduce the likelihood of calcium carbonate (the primary component of scale) precipitation.

Pre-Filtering Fill Water

Using a pre-filter when filling the hot tub can remove excess minerals from the water before they enter the tub. This simple step can significantly reduce the likelihood of scale formation.

Quality Spa Products for Scale Prevention and Removal

Leisure Time Spa offers a range of products designed specifically for scale prevention and removal in hot tubs. These products work by altering the chemical composition of the water, making it less conducive to scale formation.

  • Defender: A product designed to prevent scale by binding calcium and other minerals in the water, making them less likely to form scale.
  • Spa Up and Spa Down: Used to adjust pH and alkalinity levels, these products help maintain the water balance, reducing the risk of scale.
  • Bright & Clear: A clarifier that helps in coagulating small particles in the water, making it easier for the filtration system to remove potential scale-forming minerals.

Incorporating a PoolRX Unit

PoolRX units are an innovative solution for helping to manage scale. These units utilize a blend of minerals that include a natural de-scaler. This de-scaler works by preventing scale from easily adhering to surfaces and equipment, including the salt cell in hot tubs. As a result, surfaces and equipment remain cleaner for longer periods, reducing the need for frequent cleaning and descaling.

Integrating a PoolRX unit into a hot tub maintenance routine, especially during winter, can significantly mitigate scale build-up issues. The unit can be easily added to most hot tub systems and works continuously to keep the water balanced and free of excessive mineral deposits.

Treatment Methods

Physical Cleaning

Regularly scrubbing the hot tub’s surfaces with a brush, sponge, or abrasive pad specially designed to protect the integrity of the spa surfaces, like those from A&B Brush, can remove early signs of scale. This should be part of weekly maintenance.

Vinegar Solution

For minor scale build-up, a solution of vinegar and water can be effective. The acetic acid in vinegar helps dissolve the calcium carbonate.

Professional Descaling Agents

Severe scale may require stronger, professional-grade descaling agents. These should be used with caution and according to the manufacturer’s instructions to avoid damaging the hot tub’s surfaces.

Advanced Scale Removal Techniques

Acid Washing

For extreme cases, professional acid washing may be necessary. This process involves draining the hot tub and applying a diluted acid solution to dissolve the scale. It’s a delicate procedure that should only be performed by professionals.

Maintenance Tips for Winter

Increase Filtration Time

During winter, increasing the filtration cycle can help manage the concentration of minerals in the water.


Proper insulation of the hot tub can minimize heat loss, reducing the temperature differential that contributes to evaporation and scale formation.

Regular Covering

A well-fitted cover prevents debris from entering the tub and reduces evaporation, thereby helping control scale.


Dealing with scale build-up in hot tubs during winter requires a comprehensive approach. By understanding the causes of scale and implementing effective strategies, hot tub owners can enjoy a clean, functional hot tub throughout the colder months and beyond.

To learn more about the forward-thinking manufacturers and premier products we represent, please contact our expert team of pool and spa manufacturer reps at or locate your area’s rep on our territories page. We are ready to provide you with comprehensive information and assistance.