Calcium Hardness Increaser - Calcium Chloride Flakes

Bring soft hot tub and pool water back up to strength with food-grade calcium chloride flakes. When hardness slips under 150 ppm the water turns aggressive and foamy. A single dose returns it to the safe 150-250 ppm range.

Sizes and prices

Available in 1kg, 2.5kg, 5kg, 10kg, 20kg, 25kg.

How to use

  1. Check calcium hardness, total alkalinity and pH with a fresh strip or a liquid kit.
  2. Turn on the circulation pump and lift out the floating dispenser.
  3. Dissolve the measured dose first in a clean bucket holding about 5 L of warm tub water and stir it through.
  4. With the pump running, tip the dissolved solution gently across the water surface.
  5. Keep circulation going for a minimum of 4 hours before you bathe or retest.
  6. Retest at the 4-hour mark and only add more if hardness is still below 150 ppm.

Frequently asked questions

What calcium hardness should I aim for in a hot tub?

Keep hot tubs at 150 ppm to 250 ppm and swimming pools at 200-400 ppm.

By how much does 9 g lift calcium hardness?

Roughly 10 ppm across 1000 L of water at room temperature.

Can I use calcium chloride in an acrylic spa?

Yes, provided you dissolve it in a bucket first and add it with the pump running. Never scatter dry flakes across an acrylic shell.

How long will a 1 kg tub last?

A 1500 L hot tub uses about 25-50 g per top-up, so 1 kg gives you 20-40 doses, near enough a year of normal use.

Is it fine in a salt-water pool?

Yes. Calcium chloride works alongside salt chlorination and does not affect the cell.

Do I have to shock the tub afterwards?

No. This is a balancer rather than a sanitiser, so your sanitiser levels stay where they are.

Why choose flakes over pellets?

Flakes carry more surface area, so they dissolve faster and are far less likely to settle and pool on the shell.

Will it push up total dissolved solids (TDS)?

Yes. Every 100 ppm of added hardness raises TDS by around 280 ppm, so refresh some water if TDS climbs above 1500 ppm.

How does calcium hardness tie into LSI?

Calcium is one of the four LSI factors, alongside pH, alkalinity and temperature. Raising it steers water away from the corrosive end of the index.

Why has my water gone cloudy after dosing?

Either the flakes went in neat or pH was already above 7.8. Circulate for 24 hours, add a clarifier, and lower pH if you need to.

Can I use it to sort out scale?

No. Scale is the reverse issue; use Water Scale Inhibitor and drop pH to dissolve existing deposits.

Why is the foaming worse after dosing?

Foam that has nothing to do with softness usually comes from lotions, detergents or a poor antifoam. Clean the filter and use an antifoam made for hot tubs.

How does calcium chloride differ from calcium hypochlorite?

Calcium chloride only raises hardness, whereas calcium hypochlorite is a powerful sanitiser that also lifts pH and chlorine. The two are not interchangeable.

Flakes or prills, which is better?

Both share the same active ingredient. Flakes dissolve quicker; prills are denser and simpler to scoop. Zagosa Spa & Pool supplies flakes so they melt away fastest in heated water.