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Phosphoric Acid Storage — 85% H3PO4 Tank System Selection

Storing Phosphoric Acid? Start Here

Phosphoric acid (typically 75–85%) is the easygoing one of the strong acids — stable, predictable, and a staple in water treatment and food processing. A chemical-grade poly tank handles it with a straightforward material setup and no exotic surprises. Here's the short version.

Can you store it in a poly tank? Yes — simply.

85% phosphoric acid is compatible with chemical-service polyethylene (1.9 SG). Use Viton (FKM) gaskets, PVC fittings, and 316 stainless bolts. EPDM swells and fails in concentrated phosphoric, so stick with Viton on the wetted seals.

If it's for food or drinking-water use, specify food-grade acid and an NSF/ANSI 61 tank where the acid can reach product or finished water.

The safety that actually matters

  • It's still a strong acid — eye/skin protection, eyewash within reach, and keep it away from bases and bleach.
  • Secondary containment sized to 110% of the tank.
  • A simple atmospheric vent is enough — phosphoric doesn't off-gas aggressively like HCl.

Common questions

What gaskets for phosphoric acid?
Viton. EPDM swells and loses its seal in concentrated phosphoric within months.
Is it food-safe to store in poly?
With food-grade acid and an NSF/ANSI 61 tank, yes — phosphoric is widely used in food and beverage processing.
Does it need special venting?
No — a standard atmospheric vent with a rain cap is fine. It doesn't fume like hydrochloric acid.

Phosphoric Acid storage tanks from OneSource

For phosphoric acid storage, specify HDLPE 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.

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 Phosphoric Acid (CID 1004, CAS 7664-38-2). 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 Phosphoric Acid. cdc.gov/niosh/npg. CDC / NIOSH chemical-specific occupational-safety reference.

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