Can 3d printed things go in water? The simple answer is yes, but it doesn't happen automatically. Making a 3D print truly waterproof or water-resistant requires careful planning before, during, and after printing. While the plastic material itself keeps water out, the way 3D printers build objects—one layer at a time—creates a basic problem that needs solving. Success depends on three main things: picking the right material, setting up your printer correctly, and finishing your print properly. When you get these three parts right, you can make custom boat parts, plant growing systems, underwater camera cases, and garden containers.
This guide will show you everything you need to know about waterproof 3D printing. You will learn:
- Why regular 3D prints leak water
- How to pick the best plastic for water projects
- The exact printer settings to make watertight objects
- A clear step-by-step process for sealing parts so they last longer
- Important safety tips for fish tanks, food containers, and outdoor use
Quick Answer, Hidden Challenge
The main problem with making 3D prints waterproof is tiny holes. Even though you're using solid plastic that doesn't absorb water, the way 3D printers work naturally creates objects with small gaps. It's all about microscopic spaces.
Not Automatic: Layer Lines
Think of a 3D print like a wall made from thousands of tiny bricks (the melted plastic) stacked on top of each other. If there's no cement between those bricks, water will eventually find its way through the tiny gaps. In 3D printing, these gaps appear between each layer and between the lines of plastic within each layer. Even a print that looks completely solid has these tiny channels.
We've seen this ourselves with a simple test. We printed a 2-inch cube with standard settings using PLA plastic. After filling it with water and placing it on a paper towel, we saw small wet spots appearing on the towel within an hour. Within 24 hours, a noticeable amount of water had slowly leaked through the layer lines, proving that without special steps, a standard print only resists water but isn't truly waterproof.
Choosing The Right Material
Making a waterproof part starts with picking the right plastic. Not all 3D printing materials work the same way when exposed to water. An important feature to understand is hygroscopy—how much moisture a material soaks up from the air. Materials that absorb lots of moisture can swell, weaken, and break down when underwater for long periods, even if the print is perfectly sealed.
Below is a detailed comparison of common plastics for water projects.
| Filament | Inherent Water Resistance | Porosity Risk (Printed) | UV Resistance (Outdoor Water) | Food-Safe Potential* | Key Consideration |
|---|---|---|---|---|---|
| PLA | Low (Biodegradable) | High | Very Low | High (with caveats) | Avoid for long-term submersion; can deform in hot water. |
| PETG | High | Medium | Medium | High (with caveats) | Excellent all-rounder, balances ease of printing and performance. |
| ABS | High | Medium-Low | Low | Low (emits fumes) | Requires good ventilation and a heated bed; prone to warping. |
| ASA | Very High | Medium-Low | Very High | Low (emits fumes) | The superior choice for outdoor/UV-exposed water applications. |
| PP | Excellent | Low | High | High | Challenging to print due to warping and poor bed adhesion. |
| TPU | Excellent | Very Low | High | Medium | Flexible, great for seals/gaskets, but requires slower printing. |
PETG is often our first choice. It sticks well between layers and barely absorbs moisture. It only absorbs about 0.2% water over 24 hours, while some PLA types can absorb much more, leading to faster breakdown in water. For any part that will stay outdoors, like sprinkler parts or boat components, ASA is the best choice because it handles sunlight extremely well.
A Note on Food Safety
Even when using plastic labeled as "food-safe," the layer lines in a 3D print can collect bacteria. For a print to be truly safe for repeated contact with food or drinks, it must be sealed with a certified food-grade coating. We will cover this in the finishing section.
Your Slicer Is Defense
You can create an almost waterproof part before it even starts printing. Your slicer software (like Cura, PrusaSlicer, or Bambu Studio) is your main tool for reducing tiny holes. By adjusting specific settings, you can make the printer create a denser, more fused object.
Increase Wall/Perimeter Count
The walls, or perimeters, of your print are the first and most important barrier against water. A standard print might only have two walls. For a watertight part, we recommend at least 3 walls, and for high-pressure or long-term underwater use, 4 to 5 walls is a strong starting point. This creates a much thicker, less leaky shell.
Optimize Layer Height
There's a trade-off with layer height. A smaller layer height (like 0.12mm or 0.16mm) creates thinner layers that get squished together better, reducing the size of gaps between them. This results in a smoother surface and a tighter seal. The downside is much longer print time. For many projects, a well-tuned 0.2mm layer height can work when combined with other settings.
Use Higher Extrusion Temp
Printing at the higher end of a plastic's recommended temperature range helps layers stick together better. The hotter plastic flows more easily and forms a stronger, more complete bond with the layer below it. This "welds" the layers together, physically closing the tiny gaps. Always print a temperature test for your specific plastic to find the sweet spot that gives maximum strength without causing strings or other problems.
Increase Infill and Pattern
While the walls are the main barrier, infill plays an important role. For parts that need to handle water pressure or might get hit, a higher infill percentage (30-50%) provides internal support. More importantly, using a grid, cubic, or gyroid infill pattern ensures that even if water gets through the outer wall, it stays trapped in a small internal space rather than having a clear path through the part.
Calibrate Extrusion Flow Rate
This is perhaps the most critical and often forgotten setting. Not pushing out enough plastic is the biggest enemy of a waterproof print. If your printer isn't pushing out enough plastic, you'll have visible gaps between plastic lines, creating a mesh-like structure. From our experience, a perfectly tuned print has a smooth, shiny top surface with no gaps. A slightly over-extruded print (like a flow rate of 102-105%) can often help with water-tightness, as it forces extra plastic into any remaining holes. To calibrate, print a simple cube with a solid top layer and adjust the flow rate until the top surface is perfectly smooth and closed.
The Ultimate Sealing Workflow
For projects requiring 100% guaranteed waterproofing, especially under pressure or for long-term underwater use, a multi-step process combining design, printing, and finishing is the only reliable method.
Step 1: Design for Water
Before you even open your slicer, think about your design. If you're designing the part yourself, make sure walls are thick enough to handle the extra perimeters you'll be printing. Avoid very thin features or sharp internal corners where layers might not stick perfectly. Simple, strong shapes are easier to make waterproof.
Step 2: Print with Intent
Now, use the knowledge from the previous sections. Choose the right material for the job—like PETG for general use or ASA for outdoors. Then, use the optimized slicer settings: increase your wall count, consider a smaller layer height, print hotter, and make sure your extrusion is perfectly tuned to create the densest possible part right off the print bed.
Step 3: Seal Your Print
Even a perfectly printed part can benefit from sealing. This final step moves a part from "water-resistant" to truly "waterproof." A sealant fills any remaining tiny pores and provides an additional chemical and physical barrier.
| Sealant Type | Best For | Pros | Cons |
|---|---|---|---|
| Epoxy Resins | Maximum durability, food-safe applications (when certified), structural strength. | Fills gaps completely, very strong, often certified food-safe. | Messy application, long cure time, can be expensive. |
| Silicone Sealants | Gaskets, flexible parts, sealing joints. | Flexible, excellent water barrier. | Can be difficult to apply smoothly, may not adhere to all plastics. |
| Polyurethane Coatings | Outdoor parts, UV protection. | Durable, UV resistant, waterproof. | Strong fumes, requires good ventilation. |
| Vapor Smoothing (ABS/ASA only) | Achieving a perfect, seamless surface. | Creates a truly fused, injection-mold-like surface. | Requires specific chemicals (e.g., acetone) and significant safety precautions. |
For most rigid parts, a two-part epoxy coating is the gold standard. It creates a thick, durable, and completely waterproof shell. For parts that need to bend, like gaskets or custom seals printed with TPU, a bead of silicone sealant is the better choice.
Step 4: The Leak Test
Never use a part without testing it first. The method is simple. For a part designed to hold water (like a vase or planter), fill it completely, place it on a dry paper towel, and check back regularly over 24-48 hours for any signs of moisture. For a part meant to be underwater (like a submersible housing), place a paper towel inside it, seal it, and put it in a bucket of water for several hours. When you take it out, the internal paper towel should be perfectly dry.
Critical Safety Considerations
Using 3D prints in or around water creates responsibilities, especially when living creatures or human consumption are involved.
Aquariums And Fish Safety
This is a high-stakes situation. It's critical to ensure nothing leaks from the print into the water. We recommend using a chemically stable plastic like PETG as a base. However, the absolutely necessary final step is to completely cover the print in a certified, aquarium-safe epoxy or silicone sealant. An unsealed print, regardless of the plastic used, can potentially leak additives or colorants from the plastic, which could harm sensitive aquatic life.
The Food-Safety Challenge
As mentioned earlier, the layer lines in any 3D print can collect bacteria. This makes unsealed prints unsuitable for repeated contact with food or drink. To make a 3D printed cup, container, or utensil truly food-safe for liquid contact, you must seal the entire surface with a coating that is certified as food-grade and non-toxic after curing. An appropriate two-part epoxy is the most common and reliable solution.
Long-Term Durability Concerns
Two main forces will damage your prints over time: UV radiation and water absorption. Sunlight, specifically its UV part, will make plastics like PLA brittle and weak very quickly. PETG has better resistance, but for any part that will stay permanently outdoors in sun and rain, we only recommend ASA. It was designed for exactly this purpose. Furthermore, even a water-resistant material can slowly absorb moisture over months or years, which can lead to gradual loss of strength. For critical parts intended for long-term underwater use, a quality external sealant is essential protection.
Conclusion: Go Make a Splash!
Creating waterproof 3D printed parts is not only possible but also opens up a huge new world of functional projects. The key to success is a systematic approach. By moving away from the "print it and see" mindset and instead deliberately planning for water-tightness, you can achieve reliable and long-lasting results every time.
Remember the three pillars of success: start with the right material for the environment, fine-tune your slicer settings to create a dense and fused object, and apply the appropriate finishing sealant for a guaranteed, waterproof finish. With these principles in hand, you are now equipped to move your ideas from the digital drawing board into the water. Can 3d printed things go in water? Absolutely—when you follow the right process.