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C · Ca(OCl)2
Calcium hypochlorite
high hazardAlso: pool shock, HTH, high-test hypochlorite
The long-shelf cousin of liquid bleach. A small jar can disinfect thousands of gallons if you make a dilute stock the way EPA describes — and if you never, ever mix it with acids, ammonia, or organics.
- Shelf life
- 5–10 years dry and cool if it is unstabilized 65–73% granules
- Container
- Glass or the original HDPE, airtight, alone on its own shelf
- Grade
- 65–73% granular, no algaecide, no clarifier, no cyanuric acid (not trichlor / dichlor tablets)
What it does
- ▸Emergency drinking-water disinfection via a 1% stock solution
- ▸Surface and tool sanitation from that same dilute stock
Store
- ▸Store alone. Cool, dry, dark. Not in a hot Arizona shed.
- ▸Keep away from oils, grease, glycerin, brake fluid, solvents, fertilizers, and anything acid.
- ▸If the granules clump into a wet cake or smell violently of chlorine, isolate outdoors and get advice — it can decompose.
Hazards
- ▸Oxidizer. Can start fires with oils, glycerin, petroleum jelly, camphor.
- ▸Acid or vinegar → chlorine gas.
- ▸Ammonia → chloramine gas.
- ▸Dust burns lungs and eyes.
Never mix
Also keep away from: ammonia, oils, grease, fertilizers, any acid.
Gear
Heavy gloves · Splash goggles · Ventilate or work outdoors
In the field
EPA stock method: dissolve 1 heaping teaspoon of 65–70% granular calcium hypochlorite in 2 gallons of water. That stock is roughly 500 mg/L chlorine. Add 1 part stock to 100 parts water you will drink. Mix, wait 30 minutes, confirm a faint chlorine smell.
Do not dump granules straight into a drinking cup. Do not use stabilized trichlor tablets for drinking water.
Arizona note
Heat accelerates loss of available chlorine and raises fire risk. Interior closet, not the garage.
Source
Pool supplier. Read for ‘calcium hypochlorite’ and 65–73%. Reject anything with algaecide, copper, or ‘shock and swim’ blends.