How to Make Watertight 3D Prints That Hold Water

3D printing has evolved from rapid prototyping to functional product manufacturing, but there's one common limitation users still face: leakage. If you're designing vases, fluid containers, hydraulic parts, or any other item that requires a watertight seal, creating watertight 3D prints is essential.

But can 3D prints hold water reliably? Yes, if designed and finished correctly. This guide breaks down the science behind waterproofing 3D parts, why prints leak, and exactly how to make 3D prints watertight without sacrificing strength or function.

(Source：reepik)

Why 3D Prints Leak in the First Place

3D prints, especially FDM prints, are made layer by layer. Even with high-quality machines, microscopic gaps can form between layers or perimeter walls. These gaps aren’t visible to the naked eye but can allow air or water to pass through, especially under pressure.

Key leakage culprits include:

• Layer gaps or under-extrusion
• Low wall thickness
• Incorrect material choice
• Poor layer adhesion
• Incomplete infill/perimeters
  

To produce a truly sealed part, you'll need to optimize settings, use the right materials, and apply post-processing where necessary.

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Can 3D Prints Hold Water?

Yes, but not all by default. Materials like PLA and ABS can be used to create waterproof prints, but they’re not always reliable on their own.If you want prints to reliably hold water long-term, you need to:

• Choose the right filament
• Use proper printer settings
• Consider chemical or thermal post-processing
• Possibly seal the part afterward
  With the right approach, even FDM-printed parts can hold liquid just as well as injection-molded containers.

How to Make 3D Prints Watertight: 8 Proven Tips

Here’s a step-by-step approach to achieve watertight 3D prints from the start.

1. Use PETG, Nylon, or ASA Filament

While PLA and ABS are popular, they’re not ideal for water resistance. Instead, try:

PETG: Naturally water-resistant and better layer adhesion.

Nylon: Durable and slightly porous, but can be sealed effectively.

ASA: UV- and weather-resistant, ideal for outdoor watertight prints.

Choose a filament known for minimal shrinkage and good interlayer bonding.Check out JLC3DP guide on PETG vs ABS for durability and strength.

2. Increase Wall Thickness and Perimeters

Thin walls are leak-prone. For watertight prints:

• Use at least 1.2 to 1.6mm wall thickness.
• Set 3–5 perimeter shells for better sealing.
• Avoid “vase mode” or single-wall prints unless you plan to post-process them heavily.

3. Set 100% Infill

This one’s simple: infill matters. Low infill = more internal gaps.For best results:

• Use 100% infill for pressure vessels or containers.
• Use grid or cubic patterns for tighter bonding.

This also boosts strength.

4. Optimize Layer Height and Flow Rate

Use lower layer heights (0.1–0.2 mm) for better layer bonding. Also:

• Set flow rate to 102–105% to slightly over-extrude and fill gaps.
• Use a wider line width than the nozzle diameter for stronger adhesion.
  
  Check that the layers slightly squish into one another without bulging.

Want to push your printer further? Check out these slicer hacks to improve 3D printing that can boost layer bonding and reduce gaps, essential for watertight results.

5. Print at Higher Temperatures

Higher extrusion temperatures help melt layers together more effectively, especially for PETG or ABS.

• PETG: 240–250℃
• ABS: 230–250℃
• Nylon: 250–260℃

Use the upper end of the filament’s range and ensure the environment is warm and draft-free.

6. Use a Heated Chamber or Enclosure

If you’re printing large containers, temperature fluctuations can lead to warping and layer splitting, which increases leakage risk.

An enclosure or heated chamber helps maintain a stable thermal environment for plastics like ABS or Nylon.

7. Apply Post-Processing Sealants

Even with perfect print settings, some parts might still leak under pressure. That’s where sealants come in:

• Epoxy resin: Brush-on or dip the entire part to seal gaps.
• Silicone caulk: Great for internal linings in DIY containers.
• XTC-3D: A popular smooth epoxy coat specifically made for 3D prints.
• Plasti Dip: Spray-on flexible rubber coating.
  
  Just make sure the sealant is safe for your application (e.g., food-safe, chemical-resistant, etc.).

8. Acetone Vapor Smoothing (for ABS only)

ABS prints can be smoothed and sealed using acetone vapor. This slightly melts the surface, closing micro-gaps.

Steps:

• Place your ABS print in a sealed container with a small acetone pool (don’t submerge it).
• Let the vapor soften the surface for 10–15 mins.
• Remove and let dry in a ventilated area.
  

This enhances water resistance and surface quality.Note: Only use this method in a well-ventilated area, with proper PPE.

Test Your Print’s Waterproofing

You don’t want surprises after installation. Test watertightness by:

• Filling with water and letting it sit overnight.
• Submerg the print and applying light pressure (squeeze test).
• Use dyed water or food coloring to detect micro-leaks.
  If any dampness shows on the outer surface or bubbles appear, it needs more sealing.

Real-World Applications of Watertight 3D Prints

When executed properly, waterproof prints can be used for:

• Garden hose connectors,
• Vases and planters,
• Hydraulic enclosures,
• Aquaponics systems,
• Lab containers,
• Custom plumbing adapters.

Yes, Your 3D Prints Can Be Watertight

So, how to make a 3D print watertight? It’s not rocket science — just good design, reliable materials, and the right settings. Whether you’re making a decorative vase or a high-pressure fluid part, following the steps above will help you avoid leaks, cracks, and failed prototypes.

Master your technique, seal the deal (literally), and build parts that actually hold water.