How to Raise Pool Hardness: The Calcium Chloride Dose

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To raise pool hardness, dissolve calcium chloride in a bucket of water and add it with the pump running. The chemistry gives 111 g of pure calcium chloride per 10,000 litres for each 10 mg/L rise; one maker’s label says 100 g. NSW Health’s targets are 200–400 mg/L for concrete and 80–200 mg/L for fibreglass.

The short answer

The dose: 111 g of anhydrous calcium chloride per 10,000 L per 10 mg/L, by the chemistry (147 g if the product is the dihydrate flake). One maker’s label, for a 990 g/kg product, says 100 g.
Concrete and fibreglass have different targets. NSW Health’s 2026 public-pool guidelines: 200–400 mg/L for a masonry pool or spa, 80–200 mg/L for vinyl or fibreglass. SA Health’s home-pool range is 150–400 mg/L.
Worked example: a 40,000 L concrete pool from 100 to 200 mg/L takes 4.4 kg by the chemistry, 4.0 kg on the label rate. Add half, run the pump 6–8 hours, retest, then add the rest.
Check the saturation index, not just the number. With NSW Health’s factors, pH 7.4, alkalinity 100, 29°C: calcium 100 gives -0.4 (corrosive side); 200 gives -0.1, inside NSW Health’s −0.3 to +0.3.
Calcium only comes down by replacing water, NSW and Queensland Health both say, so stop short of the target rather than overshoot it.

The calcium chloride dose ladder: how much to add to raise calcium hardness by 50 or 100 mg/L, by pool volume (chemistry: anhydrous calcium chloride, 1.109 g per 1,000 L per mg/L as CaCO3; label: one maker’s published rate of 100 g per 10,000 L per 10 ppm for a 990 g/kg product; read 16 October 2026)
Pool volume	Raise by 50 mg/L	Raise by 100 mg/L
30,000 L	1.7 kg by the chemistry; 1.5 kg on one maker’s label	3.3 kg by the chemistry; 3.0 kg on one maker’s label
50,000 L	2.8 kg by the chemistry; 2.5 kg on one maker’s label	5.5 kg by the chemistry; 5.0 kg on one maker’s label
70,000 L	3.9 kg by the chemistry; 3.5 kg on one maker’s label	7.8 kg by the chemistry; 7.0 kg on one maker’s label

How do I raise the calcium hardness in my pool?

Calcium hardness is raised with calcium chloride. NSW Health’s 2026 guidelines and Queensland Health’s public-pool guidelines say the same thing in the same words: if calcium hardness needs to be raised, it can be increased by adding calcium chloride; if it needs to come down, water has to be exchanged for lower-calcium make-up water.

Test first. Calcium hardness, pH and total alkalinity, with the same kit. SA Health says calcium hardness should be checked once a week.
Work out the dose. Grams = rise in mg/L × pool litres ÷ 1,000 × 1.109 for pure anhydrous calcium chloride. Divide by the product’s strength if it is less than 100%. For the dihydrate flake, use 1.469 instead of 1.109.
Dissolve it in a bucket of water, as one maker’s label directs, and pour the solution into the pool with the pump running.
Add half, wait, retest. The same label says to run the pump and filter at least 6–8 hours before retesting, and not to add it within 2–4 hours of an alkalinity increaser, which it says can make the water extremely cloudy.
Finish at the bottom of your band, not the top. Calcium does not get used up, and the only way down is draining.

Worked example. A 40,000 L concrete pool reads 100 mg/L and you want 200. Rise 100 mg/L × 40,000 ÷ 1,000 × 1.109 = 4,435 g, about 4.4 kg of anhydrous calcium chloride. The maker’s label rate gives 4,000 g. Add 2 kg, run the pump overnight, retest, and dose the remainder from the new reading.

The chemistry and the label disagree by about 10%: on the arithmetic, 100 g of a 990 g/kg product raises 10,000 L by about 9 mg/L, not 10. Dosing in two steps and retesting makes the difference irrelevant.

The quotable rule: calcium chloride raises pool hardness by about 10 mg/L per 111 g in 10,000 litres, and because calcium only leaves with the water, add half the dose, retest, then add the rest.

What should calcium hardness be in a concrete or fibreglass pool?

It depends on the surface, and the published figures do not all agree:

Source	Concrete, pebble or tiled (masonry)	Fibreglass or vinyl	Who it is written for
NSW Health Guidelines for Managing Water Quality in Public Swimming Pools and Spa Pools, 2026 (Appendix E)	200–400 mg/L	80–200 mg/L	Public pools and spas
SA Health, Pools at home and maintaining them	150–400 mg/L (one range for all home pools)	150–400 mg/L	Home pools
One calcium chloride maker’s label (maker-published)	200–400 ppm	150–250 ppm	Home pools

The reason the masonry figure is higher is in both health guidelines: water should hold enough calcium that it does not damage concrete surfaces or tile grout, but not so much that scale forms. Our reading: a fibreglass or vinyl shell has no cement surface for under-saturated water to draw on, which is why its band starts lower.

Where the sources disagree, use the overlap. The overlap rule: 200–400 mg/L satisfies all three sources for a concrete pool; 150–200 mg/L satisfies all three for fibreglass. A fibreglass pool reading 180 does not need calcium; a concrete pool reading 180 does.

If your pool is cloudy or scaling at the waterline, the calcium is more likely too high than too low: why a pool goes cloudy and how to clean calcium off pool tiles cover that side, and this page does not repeat them.

Do I need to raise calcium hardness? Check the saturation index first

A low calcium reading matters because of what it does to the water balance, and the balance is measured with the Langelier Saturation Index. NSW Health’s 2026 guidelines give the formula: LSI = pH + temperature factor + calcium hardness factor + total alkalinity factor − total dissolved solids factor (12.1 below 1,000 mg/L TDS, 12.2 above). They put the ideal at 0 or slightly positive, within −0.3 to +0.3; negative water is corrosive and can damage fixtures and fittings.

Worked example, using NSW Health’s Table E-1 factors. pH 7.4, total alkalinity 100 mg/L (factor 2.0), water 29°C (0.7), calcium 100 mg/L (1.6): LSI = 7.4 + 0.7 + 1.6 + 2.0 − 12.1 = -0.4, outside the range on the corrosive side. Raise calcium to 200 mg/L (factor 1.9) and it becomes -0.1, inside it.

In a salt pool the dissolved solids are well over 1,000 mg/L, so the last term is 12.2 and the same water reads -0.5 before and -0.2 after. NSW Health also says to deduct 30% of the cyanuric acid reading from total alkalinity in a stabilised outdoor pool, which pulls the index down a little further.

So if pH and alkalinity are low too, fix those first; they move the index as much as calcium does and come back down more easily. The doses are on how to raise pH in a pool and how to raise alkalinity without raising pH.

Raise calcium when the index is below −0.3 and calcium is under your surface’s band; if the index is already in range, leave the calcium alone.

Raising hardness in a salt chlorinator pool

HealthyWA says salt water chlorinators are prone to a build-up of white scale on the electrodes, particularly if the water contains high levels of calcium, and that scale reduces the cell’s chlorine output. That is a reason to stay at the low end of the band in a salt pool, not a reason to run it low: corrosive water attacks a concrete interior regardless of how it is chlorinated.

One maker’s label adds two practical notes: calcium is more likely to come out of solution in warmer water, and low calcium hardness can make water foam. If the pool is foaming, why pool water foams covers the other causes first.

Why the cell scales and what it costs to replace are on why a chlorinator stops making chlorine and salt cell replacement cost.

If you overshoot: what bringing calcium down costs

There is no chemical that takes calcium out of a pool at home. NSW Health: exchange the water with make-up water containing lower levels of calcium hardness. Queensland Health says the same; NSW Health notes that lowering calcium hardness is not always possible because of the composition of the fill water.

So know your tap water’s hardness before you aim high: if mains water arrives at 150 mg/L, a fibreglass pool overdosed to 300 can only be diluted towards 150. Replacing a third of a 50,000 L pool is about 16.7 kL of water; what filling a pool costs and what emptying and refilling costs price it at each water utility’s tariff.

If the surface itself is etched or the grout is washing out after years of soft water, that is a resurfacing question; pool resurfacing cost by interior compares the finishes, and you can compare pool quotes on the same written scope.

Common questions

How do I raise the hardness in my pool?

Add calcium chloride, dissolved in a bucket of water, with the pump running. NSW Health’s 2026 pool water guidelines name calcium chloride as the chemical that raises calcium hardness.

How much calcium chloride do I add to raise hardness by 10 ppm?

About 111 g of pure anhydrous calcium chloride per 10,000 litres by the chemistry, or 147 g of the dihydrate flake. One maker’s label says 100 g of its 990 g/kg product. Add half and retest after 6–8 hours.

What should calcium hardness be in a fibreglass pool?

NSW Health’s 2026 guidelines say 80–200 mg/L for vinyl or fibreglass. SA Health gives 150–400 mg/L for all home pools and one maker’s label 150–250, so 150–200 mg/L satisfies all three.

What should calcium hardness be in a concrete pool?

200–400 mg/L for a masonry pool on NSW Health’s 2026 guidelines, the same as one maker’s label; SA Health’s home range is 150–400 mg/L.

Can I use bicarb or soda ash to raise calcium hardness?

No. Bicarb raises alkalinity and soda ash raises pH; neither adds calcium. NSW Health names calcium chloride for calcium hardness.

Sources

General information only, current at 2026-10-16. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.

How to raise pool hardness