Top 10 Best calcium hardness increaser in 2026

Last Updated - 6/7/2026

🏆Best Choice

Clorox Pool & Spa

Clorox® Pool&Spa™ Swimming Pool Calcium Hardness Increaser, Prevents Corrosion, Etching and Staining, 4LB (Pack of 1)

9.8

ChoiceComparer.com Score

9.8

/ 10

Outstanding

Main highlights

•Prevents Corrosion, Etching, and Staining: With Clorox Pool&Spa Swimming Pool Calcium Hardness Increaser, you can safeguard your pool against corrosion, etching, and staining, ensuring its longevity and pristine appearance. Our product offers reliable protection, giving you peace of mind while you enjoy your pool.
•Increases Low Total Hardness Levels: This product helps increase the low total hardness levels in swimming pool water, ensuring a balanced and stable environment for your pool. It restores water parameters to their ideal ranges.
•Extends Equipment Life: Unbalanced water can cause a corrosive environment that damages your pool surfaces or equipment. This product prevents pool surface damage, reduces pool maintenance, extending the life of your pool's cleanliness.
•Compatibility: Our Clorox Pool&Spa Swimming Pool Calcium Hardness Increaser is ideal for plaster pools and areas with soft water.
•Clorox Pool App: Test like an expert anytime, anywhere with the Clorox Pool App. Solve common swimming pool problems and get personalized product and dosage recommendations.

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$11.82

$12.99

-9%

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MAV AquaDoc

MAV AquaDoc Calcium Hardness Increaser Hot Tub Owners Rely On, Calcium Booster for Hot Tubs & Spas

9.6

ChoiceComparer.com Score

9.6

/ 10

Outstanding

Main highlights

•Make balancing your water easier & more cost effective with AquaDoc's calcium hardness increaser. Our spa calcium hardness increaser is vital to ensuring proper water hardness levels in your hot tub. AquaDoc's Calcium Booster gets your hardness up.
•Avoid corrosion, etching, and staining - AquaDoc's Professional Grade Hot Tub Calcium increaser is your best defense against soft water in your hot tub or spa. Guard calcium levels from decreasing too low with our spa Calcium booster for hot tubs.
•How it works - AquaDoc's Hot Tub Calcium hardness Increaser works to raise your water's hardness level to ensure properly balanced hot tub water. Our spa hardness increaser easily works to raise your Calcium levels by 10ppm increments or more.
•The Hardness Increaser Hot Tub Owners Love - When it comes to Spa Chemicals calcium hardness increaser is a must have. Without hot tub chemicals calcium hardness can become unbalanced. Always have a hot tub calcium booster ready and waiting.
•Easy to Use, Made in the USA - (1) Check your calcium levels, (2) 1 ounce of AquaDoc's Calcium increaser will boost water's hardness level by 10ppm. (3) After determining hardness level goal, add proper amount of increaser while equipment is on. (4) Run filter for 1 - 2 hours, wait 20 minutes, then retest water.

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$19.99

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SpaGuard

SpaGuard Spa Calcium Hardness Increaser - 12 Ounce

9.5

ChoiceComparer.com Score

9.5

/ 10

Outstanding

Main highlights

•Prevents corrosion of equipment due to low calcium hardness
•Prevents etching of plaster due to low calcium hardness
•Calcium Hardness Increaser

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$12.99

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SpaChoice

SpaChoice 1-Quart Premium Increase Calcium, Liquid Calcium Hardness Increaser Hot Tub, Made in USA

9.3

ChoiceComparer.com Score

9.3

/ 10

Excellent

Main highlights

•The ideal hardness level is 200-400 ppm
•1 ounce of product per 500 gallons increases hardness by about 10 ppm
•Customers prefer this liquid product as it can be easier to use than granular alternatives

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$12.87

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Robelle

Robelle 25-Pounds Premium Pool Calcium Up, Calcium Hardness Increaser

9.2

ChoiceComparer.com Score

9.2

/ 10

Excellent

Main highlights

•Calcium chloride for pools
•Rapidly increases total hardness
•Helps prevent corrosion or etching of pools
•Ideal calcium hardness range 200 - 400 ppm
•8 ounces raises calcium hardness level 10 ppm per 5,000 gallons of water
•Prevents the staining or etching of your pool's surface
•Low calcium hardness level can cause water issues

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$42.41

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In The Swim

In The Swim Calcium Hardness Increaser for Swimming Pools - Fast-Acting, Scale Prevention - 94% Calcium Chloride - 45 Pounds

9.0

ChoiceComparer.com Score

9.0

/ 10

Great

Main highlights

•Boost Water Quality: Prevent cloudy, dull water by restoring the right calcium levels in your pool
•Protect Your Pool: Helps stop costly damage like corrosion and pitting on pool surfaces and equipment
•Easy-to-Use Granules: Fast-dissolving formula works quickly—just measure, pour, and circulate
•Dial in the Perfect Balance: Raise hardness 50 ppm per 6 lbs per 10,000 gallons—easy, accurate, and powerful
•Multi-Use Chemical: Highly effective for swimming pools—and also serves as an industrial-grade ice and snow melt

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$69.99

$90.54

-23%

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Pool Mate

Pool Mate 8-Pounds Premium Calcium Hardness Increaser for Pools, 100% Calcium Chloride

8.8

ChoiceComparer.com Score

8.8

/ 10

Great

Main highlights

•Calcium chloride for pools
•Rapidly increases total hardness
•Helps prevent corrosion or etching of pools
•Ideal calcium hardness range 200 - 400 ppm
•8 ounces raises calcium hardness level 10 ppm per 5,000 gallons of water
•Prevents the staining or etching of your pool's surface
•Low calcium hardness level can cause water issues

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$25.61

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SpaChoice

SpaChoice 14-Ounces Premium Increase Calcium, Calcium Hardness Increaser Hot Tub, Made in USA

8.7

ChoiceComparer.com Score

8.7

/ 10

Good

Main highlights

•The ideal hardness level is 200-400 ppm
•1 ounce of product per 500 gallons increases hardness by about 10 ppm
•This product is used to increase the calcium hardness in spas and hot tubs

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$12.49

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Robelle

Robelle 4-Pounds Premium Pool Calcium Up, Calcium Hardness Increaser, Made in USA

8.5

ChoiceComparer.com Score

8.5

/ 10

Good

Main highlights

•Calcium chloride for pools
•Rapidly increases total hardness
•Helps prevent corrosion or etching of pools
•Ideal calcium hardness range 200 - 400 ppm
•8 ounces raises calcium hardness level 10 ppm per 5,000 gallons of water

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$19.60

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