PooloraHow much calcium chloride to add to a pool
Calcium hardness protects plaster from being etched. Calcium chloride raises it; here is how much for your pool size and product.
- 15,000 gallons, calcium +10 ppm: 1.5 lb (24 oz · 670 g) of 94% calcium chloride.
- Plaster pools: 200–400 ppm (National Plasterers Council).
- It heats up when it dissolves: add it to water, slowly.
Chart: calcium chloride 94% (pellets or anhydrous)
| Pool size | +10 ppm | +50 ppm | +100 ppm |
|---|---|---|---|
| 5,000 gal | 8 oz 225 g | 2.5 lb 1.1 kg | 4.9 lb 2.25 kg |
| 10,000 gal | 16 oz 445 g | 4.9 lb 2.25 kg | 9.8 lb 4.45 kg |
| 15,000 gal | 1.5 lb 670 g | 7.4 lb 3.35 kg | 14.8 lb 6.7 kg |
| 20,000 gal | 2 lb 895 g | 9.8 lb 4.45 kg | 19.7 lb 8.95 kg |
| 25,000 gal | 2.5 lb 1.1 kg | 12.3 lb 5.6 kg | 24.6 lb 11.15 kg |
| 30,000 gal | 3 lb 1.35 kg | 14.8 lb 6.7 kg | 29.5 lb 13.4 kg |
Chart: calcium chloride 77% (flakes)
| Pool size | +10 ppm | +50 ppm | +100 ppm |
|---|---|---|---|
| 5,000 gal | 9.5 oz 275 g | 3 lb 1.35 kg | 6 lb 2.75 kg |
| 10,000 gal | 1.2 lb 545 g | 6 lb 2.75 kg | 12 lb 5.45 kg |
| 15,000 gal | 1.8 lb 820 g | 9 lb 4.1 kg | 18 lb 8.2 kg |
| 20,000 gal | 2.4 lb 1.1 kg | 12 lb 5.45 kg | 24 lb 10.9 kg |
| 25,000 gal | 3 lb 1.35 kg | 15 lb 6.8 kg | 30 lb 13.65 kg |
| 30,000 gal | 3.6 lb 1.65 kg | 18 lb 8.2 kg | 36.1 lb 16.35 kg |
Work out your dose
Example: a 20,000-gallon plaster pool reads calcium 150 and you aim for 250. That is +100 ppm: 19.7 lb (315 oz · 8.95 kg) of 94% calcium chloride, or 24 lb (385 oz · 10.9 kg) of 77% flakes. Add it in two or three parts.
Where to aim
The National Plasterers Council recommends 200–400 ppm for plaster; ANSI/APSP/ICC-11 sets absolute limits of 150–1,000 ppm. Calcium only comes down by replacing water, so raise it in steps. Check water balance (CSI) after a big change: high calcium with high pH can scale.
Add it safely
- Calcium chloride releases heat as it dissolves. Fill a bucket with pool water first, then add the calcium slowly, never the other way around.
- Pour the solution around the pool with the pump running.
- Gloves and eye protection; keep it dry in storage.
Common questions
Why two charts?
Pellets are usually 94% or more calcium chloride; flakes are usually about 77% because they contain water. Use the percentage on your label.
Does cal-hypo add calcium too?
Yes. Calcium hypochlorite adds about 7 ppm of calcium for every 10 ppm of chlorine, which adds up if you shock with it often.
Do it with your own products
Poolora turns your test into the exact amount of the products on your shelf, in cups and ounces, in the right order, and tells you when it's safe to swim. Free to start; every chemical, water balance and history are part of Pro.
Keep going
Sources
- National Plasterers Council (NPC): calcium hardness 200–400 ppm
- ANSI/APSP/ICC-11 (calcium hardness 150–1,000 ppm)
- Doses: Poolora engine (mass balance by product and strength; pH by a carbonate-equilibrium model with constants from the USGS PHREEQC database)