Skip to main content

Calcium Hypochlorite Storage — 65-70% HTH Tank System Selection

Storing Calcium Hypochlorite (Cal-Hypo)? Start Here

Calcium hypochlorite — pool/"shock" chlorine — ships as a 65–70% granular solid and gets dissolved on site to a 1–15% solution for disinfection. The dissolved solution stores fine in a poly tank. The part to respect is the dry solid: it's a strong oxidizer that has to be kept well away from anything burnable.

Can you store the solution in a poly tank? Yes.

A 1–15% cal-hypo solution is compatible with HDPE and XLPE tanks at room temperature (ease off as concentration and heat climb). Like all the chlorine chemistries, it stains and off-gasses a little chlorine, so vent the tank and don't seal it gas-tight. Stainless is marginal in strong chlorine — poly is the better, more durable choice.

The safety that actually matters (the dry solid)

  • Keep the granules away from anything burnable — fuel, oil, grease rags, organics, and especially acids and ammonia. Contact can start a fire or release chlorine gas. Segregate by 20+ feet or a non-combustible barrier.
  • Dissolve into water (add solid to water), in a clean, dedicated container — never one that held organics or another chemical.
  • Vent + 110% containment for the solution day tank.

Common questions

Can I store cal-hypo near acid?
No — cal-hypo plus acid makes chlorine gas. Keep them separated with their own containment.
Poly or stainless for the solution?
Poly. Stainless pits in strong chlorine. Use a vented HDPE/XLPE day tank.
Why does it need venting?
It slowly releases chlorine/oxygen — a sealed tank can pressurize. Use an open atmospheric vent.

Calcium Hypochlorite storage tanks from OneSource

For calcium hypochlorite storage, specify HDPE rated to specific gravity 1.9. Verified, compatibility-matched options:

Confirm chemical compatibility and a ZIP freight quote with our team at 866-418-1777.

Strong oxidizer? Resin and material choice make or break it.

Oxidizers degrade the wrong resins and passivation layers. These guides cover oxidizer-rated construction and containment.

Explore: FRP & Fiberglass Tanks  ·  Double Wall Tanks  ·  Chemical Compatibility

Sources & References

All compatibility ratings, hazard classifications, and chemical identifiers on this page are sourced from authoritative third-party publications. Verify against the original references before final specification.

  1. PubChem Compound Database — entry for Calcium Hypochlorite (CID 24504, CAS 7778-54-3). pubchem.ncbi.nlm.nih.gov. National Library of Medicine / NCBI. Canonical chemical-identity reference.
  2. Snyder Industries Chemical Resistance Recommendations — system-of-construction guidance for polyethylene chemical-storage tanks at industrial ASTM 1.9 SG design rating. SNY-3041 Chemical Resistance Chart. Snyder Industries, current edition. Resin + fitting + gasket + bolt MOC matrix.
  3. Equistar Technical Tip — Chemical Resistance of Polyethylene — LDPE / MDPE / HDPE rating chart by concentration and temperature, distributed by Enduraplas. enduraplas.com (PDF). Equistar polyethylene resin chemical-resistance data, distributed via Enduraplas.
  4. NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response. nfpa.org. NFPA 704 'fire diamond' health/flammability/instability/special-hazard rating system (0–4 scale).
  5. UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS), current revision. unece.org/transport/ghs. GHS pictograms, signal words, and H-statement codes referenced in this guide.
  6. ASTM D1998 — Standard Specification for Polyethylene Upright Storage Tanks, current edition. astm.org. Cited as the design-specific-gravity standard (typically 1.9 SG) for industrial chemical-service polyethylene tanks.
  7. NIOSH Pocket Guide to Chemical Hazards — occupational exposure limits, PPE, and IDLH data for Calcium Hypochlorite. cdc.gov/niosh/npg. CDC / NIOSH chemical-specific occupational-safety reference.

!