Is PLA safe for water containers?

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Is PLA safe for water containers?

For cold water, yes. PLA (polylactic acid) is insoluble in water, absorbs 0.43 percent at saturation on Bambu Lab’s data sheet, and Prusa Research’s PLA flower pots showed no leakage. Two limits apply: PLA softens above 60 °C, and Prusa does not recommend any print as a food container because layer grooves harbor bacteria.

PLA and water

The water itself does no harm. Bambu Lab lists PLA Basic as insoluble in water with a saturated water absorption of 0.43 percent at 25 °C and 55 percent relative humidity. Prusa’s first watertight test addressed the claim that PLA partially dissolves: over a long test period its Prusament PLA flower pots showed no leakage at all. In the second test, PLA boxes stayed dry 20 m underwater with no coating.

PLA does need walls. Prusa’s vase test found PLA needed 4 perimeters to hold water, against 2 for ASA or PP. The counts are on the perimeter page.

Where PLA fails: heat

The Prusa Knowledge Base says PLA gets soft and deforms at temperatures over 60 °C. Bambu Lab measures a glass transition of 60 °C and a heat deflection temperature of 57 °C at 0.45 MPa. Prusa’s own yellow PLA print deformed in a car on a summer day.

That rules out hot water, a sunny windowsill for a filled container, and the dishwasher. Materials that survive a rinse cycle are on the dishwasher page. Prusa also notes PLA degrades under UV light, so an outdoor container is a job for PETG (glycol-modified PET) or ASA (acrylonitrile styrene acrylate). The filament table compares them.

Do 3D prints absorb water over time?

A little, and it plateaus. Data sheets give the saturated figure, the point past which the plastic takes up no more:

Material Saturated water absorption Conditions Source
PLA 0.43 percent 25 °C, 55 percent relative humidity (RH) Bambu Lab PLA Basic
PETG 0.45 percent 25 °C, 55 percent RH Bambu Lab PETG Basic
ASA 0.17 percent after 7 days 24 °C, 22 percent RH Prusament ASA

These are air-humidity figures, not immersion, and none of the sheets states a change in strength at saturation. Prusa’s evidence for PLA in long contact with water is the flower pots, which stayed sound for the length of its test.

Is a PLA container food safe?

Prusa’s answer is no by default. Its Knowledge Base states plainly that it does not recommend using 3D prints as food containers. The grooves between layers are almost impossible to clean and hold residue, so they become a seedbed for bacteria. That applies to PLA, PETG and every other filament equally.

The material itself is not the problem. The Knowledge Base calls PLA food-safe as a material, and Prusa’s food-grade study says most of its PLA and PETG colors use inorganic non-migratory pigments, with PLA Army Green the exception. Prusa holds no certification for them and says food-grade prints from its filaments are for personal use, not for sale. Most ABS and ASA filaments it calls rather unsafe for food contact.

Two more parts matter:

  • The nozzle. Brass contains lead and wears into the print. Prusa recommends a stainless steel nozzle for food-contact parts.
  • The surface. Prusa’s lab test ran 14 days of simulated use. The untreated print grew the largest bacterial colonies. A print coated in Efkoresin Art UV, an epoxy certified to EU regulation 10/2011, grew none.

Even coated, Prusa limits the part to cold use: no chopping boards, hot soups, microwaves or dishwashers.

What to print for water

  • Cold water, no food: PLA with 4 perimeters, tested with the leak test.
  • Outdoor or warm water: PETG or ASA, per the Prusa outdoor ratings.
  • Drinking water or food: a certified food-contact epoxy over the print, a stainless nozzle, personal use only, cold contents.

Sources

  1. PLA (Prusa Knowledge Base) (accessed September 23, 2026)
  2. Bambu Filament Technical Data Sheet V3.0, PLA Basic (accessed September 23, 2026)
  3. Bambu Filament Technical Data Sheet V3.0, PETG Basic (accessed September 23, 2026)
  4. Prusament ASA Technical Datasheet, Version 1.1 (Prusa Polymers) (accessed September 23, 2026)
  5. Watertight 3D printing PT1: Vases, cups and other open models (Prusa Research blog) (accessed September 23, 2026)
  6. Watertight 3D printing part 2: Airtight closable models (Prusa Research blog) (accessed September 23, 2026)
  7. Food safe FDM printing (Prusa Knowledge Base) (accessed September 23, 2026)
  8. How to make food-grade 3D printed models (Prusa Research blog) (accessed September 23, 2026)