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Potassium Hydroxide (Caustic Potash) Storage — Tank System Selection

Storing Potassium Hydroxide (KOH)? Start Here

Potassium hydroxide — caustic potash — is a strong base used in soap making, biodiesel, and industrial cleaning. It's an easy, low-corrosion chemical to store in poly, with one gasket rule that trips people up: use EPDM, not Viton. Viton gets attacked by strong bases.

Can you store it in a poly tank? Easily.

KOH solution is compatible with HDPE and XLPE chemical-service tanks (1.9 SG). Use EPDM gaskets, PVC fittings, and 316 stainless bolts. EPDM is the correct gasket — Viton degrades in strong caustic. Poly itself shrugs KOH off; the care is in seals and temperature.

The safety that actually matters

  • EPDM gaskets — not Viton (strong bases attack Viton).
  • Dilution gives off heat — add KOH to water slowly, never the reverse.
  • Strongly caustic — eye/skin protection, eyewash/shower nearby, 110% containment.
  • Keep concentrated solution from getting cold, which can cause it to thicken or crystallize — insulate or heat outdoor tanks.

Common questions

Viton or EPDM for KOH?
EPDM. Strong bases attack Viton — same rule as sodium hydroxide.
Is KOH hard on poly tanks?
No — polyethylene handles caustics well. The attention goes to seals and keeping it warm enough to stay pumpable.
Anything when diluting?
It releases heat — add caustic to water slowly and protect your skin and eyes.

Potassium Hydroxide (Caustic Potash) storage tanks from OneSource

For potassium hydroxide (caustic potash) storage, specify either HDLPE or crosslinked polyethylene (XLPE) 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.

Caustic or alkaline service: pick a polymer or FRP that lasts.

Strong bases stress-crack the wrong materials. These guides cover the material-of-construction call for caustic and alkaline storage.

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 Potassium Hydroxide (CID 14797, CAS 1310-58-3). 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 Potassium Hydroxide. cdc.gov/niosh/npg. CDC / NIOSH chemical-specific occupational-safety reference.

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