How much calcium chloride to add to a pool?
Raising calcium hardness from 150 to 250 ppm in a 15,000 gallon pool takes about 16.33 lb of 83–87% calcium chloride, or 1.63 lb (26.1 oz) for every 10 ppm.
How to work it out
- In short: the calcium to add is the rise you want times your pool’s size, adjusted for how pure your product is.
- Rise: 250 − 150 = 100 ppm (as calcium carbonate)
- 100 mg/L × 56,781 L × (111 ÷ 100 for calcium chloride) = 6,296 g of pure calcium chloride
- ÷ 85% = 16.33 lb
A 100 ppm boost is a typical job for a plaster pool filled from soft water, or after a big rainy season. It is also enough calcium chloride that the dissolving heat and the bucket work matter.
Adjust for your project
- Per 10 ppm in this pool
- 1.63 lb (26.1 oz)
- Hardness rise
- 100 ppm
- Calcium chloride gets hot as it dissolves. Pre-dissolve it in a bucket of pool water — chemical into water, a little at a time — then pour it around the deep end with the pump running.
- If you shock with cal-hypo, it adds calcium too — about 0.71 ppm of hardness per ppm of chlorine.
15,000 gallons from 150 ppm, by target hardness
| Target CH | Calcium chloride to add |
|---|---|
| 200 ppm | 8.17 lb |
| 250 ppm | 16.33 lb |
| 300 ppm | 24.5 lb |
| 350 ppm | 32.66 lb |
| 400 ppm | 40.83 lb |
Doing a 100 ppm rise
At 15,000 gallons each 10 ppm takes about 1.6 lb of 85% flake, so 100 ppm is about 16 lb — a few bags of most hardness increasers. With the purer anhydrous pellets it is about 14.5 lb.
- Split it. Three additions of about 5–6 lb each, a few hours apart with the pump running, keeps the water from clouding and lets you stop if the test reaches target early.
- Hot buckets. Dissolving 5 lb of calcium chloride in a 5-gallon bucket of pool water makes the water noticeably hot. Add the flakes slowly to the water, stir with a plastic paddle, and wear gloves and goggles.
- Check the balance afterwards. A rise from 150 to 250 ppm moves the saturation index up by roughly 0.2 at the same pH and alkalinity. Run the new numbers through the saturation index calculator.
- Store it dry. Calcium chloride pulls moisture from the air and cakes in an open bag.
If hardness is too high instead, only fresh water fixes it — the drain and refill calculator does the math, as in how much water to drain to lower salt. For alkalinity, see how much baking soda to raise alkalinity in a 10,000 gallon pool.
Different size? Use the full Calcium Hardness Calculator.
What you’ll need
- Calcium hardness increaser (calcium chloride)Budget price
Raises calcium hardness. It heats up as it dissolves — pre-dissolve in a bucket of pool water, adding the chemical to the water.
See options on Amazon (opens in a new tab) - Chemical-resistant glovesBudget price
Long-cuff nitrile gloves for handling acid, chlorine and calcium chloride.
See options on Amazon (opens in a new tab) - 5-gallon bucket (one per chemical)Budget price
For pre-dissolving granular chemicals in pool water. Label each one so chlorine and acid never share a bucket.
See options on Amazon (opens in a new tab)
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Frequently asked questions
How much calcium chloride to raise hardness 50 ppm in 10,000 gallons?
About 5.44 lb of 83–87% calcium chloride.
How much calcium hardness increaser to add to a 400 gallon hot tub, 100 to 150 ppm?
About 3.48 oz of 83–87% calcium chloride — follow the spa product’s own measure if it differs.
How much anhydrous calcium chloride for 15,000 gallons, 150 to 250 ppm?
About 14.53 lb of 94–97% pellets.
Sources
- OxyChem — Calcium chloride for pools and spas (opens in a new tab) — Pool grades: anhydrous 94–97% mini-pellets and 83–87% granular/flake; “One pound of calcium chloride raises the hardness of 10,000 gallons of water by approximately 10 ppm.”
- Leslie’s — Hardness Plus label (opens in a new tab) — “Adding 1.25 pounds of hardness plus to 10,000 gallons of water will raise the calcium hardness by 10 ppm.”
- CDC — Model Aquatic Health Code, 5th edition (2024), code (opens in a new tab) — Free chlorine minimum 1.0 ppm (2.0 with CYA, 3.0 in spas); pH 7.0–7.8; CYA at or below 90 ppm; CYA:FC above 45:1 is an imminent hazard; TA 60–180 ppm; turnover tables.
- Taylor Technologies — Using the Taylor circular Watergram (opens in a new tab) — Saturation index = pH + temperature factor + log CH + log carbonate alkalinity − constant; within ±0.5 of zero needs no adjustment.
- US EPA label 57787-18 — calcium hypochlorite 65% (opens in a new tab) — 65% available chlorine; 2 oz per 10,000 gallons raises chlorine about 1 ppm; superchlorinate with 10 oz per 10,000 gallons.
- CDC — Pool chemical injuries press release (2014) (opens in a new tab) — Never mix pool chemicals, especially chlorine products with acid; add chemical to water, never water to chemical.