Can You Make 3D Prints Waterproof? A Complete Guide to Sealing Success

Why Aren’t 3D Prints Waterproof by Default?

To fix a problem, you first need to understand its root causes. The two main enemies of a watertight 3D print are layer adhesion gaps and material water absorption.

How Do Layer Gaps Cause Leaks?

FDM 3D printers build objects one layer at a time. Even with a perfectly calibrated machine, the bond between these layers is a potential weak point. If the extrusion temperature is slightly off or the layer adhesion isn’t optimal, microscopic channels can form. These channels act like a network of tiny capillaries, allowing water to slowly wick through the part over time.

What is Material Water Absorption?

Beyond layer gaps, the plastic itself can be the issue. Some materials are hygroscopic, meaning they naturally absorb moisture from the air or direct contact. This doesn’t just cause leaks; it can weaken the part. For example, a nylon (PA) part might not show visible leaks but can absorb over 5% of its weight in water, swelling and losing structural integrity. This is a critical distinction: a part can appear sealed but still fail due to material degradation from moisture.

How to Make Waterproof 3D Prints: A Three-Step Strategy

You can overcome these challenges by following a systematic approach. Think of it as building a defense in depth: start with the right foundation, reinforce the structure, and finally, apply a protective shield.

Step 1: Choose the Right Water-Resistant Material

Your material choice is the most critical decision. It sets the ceiling for your part’s potential waterproof performance. Not all filaments are created equal.

Common 3D Printing Material Water Resistance Guide

• Case Study: A study by Sculpteo subjected 3D printed parts to pressure equivalent to 100 meters of depth. Polypropylene (PP) was the only material that passed all long-term immersion tests without absorbing measurable water, making it uniquely suited for truly waterproof applications.

Step 2: Optimize Slicer Settings for a Dense Structure

With the right filament loaded, your slicer settings are your next line of defense. The goal is to create the most dense, gap-free print possible.

• Increase Wall/Perimeter Count: Don’t rely on just 2 walls. Using 3 to 5 perimeter walls creates a thicker, more tortuous path for water to penetrate before it even reaches the infill.
• Maximize Infill Density: For a part that must hold pressure or be submerged, 100% infill density is often necessary. This eliminates internal cavities where water can pool or travel. For less critical parts, 80%+ is a good target.
• Adjust Layer Height: A moderate layer height (like 0.2mm) can sometimes produce better layer bonding than an extremely fine layer, as it allows for more substantial material deposition.
• Calibrate Flow and Temperature: Slightly increasing your extrusion flow rate (to 102-105%) can ensure layers are pressed together firmly. Always print at the optimal temperature for your filament to ensure strong interlayer fusion.

Step 3: Apply a Post-Processing Sealant

For guaranteed waterproofing, especially with FDM prints, a sealant is your final, most effective step. Sealants fill the microscopic valleys between layer lines and create a continuous, non-porous barrier.

• Epoxy Resin: The best-performing option. A thin coat of a two-part clear epoxy (like XTC-3D) creates a hard, impermeable shell. It’s ideal for parts that will be submerged or exposed to weather.
• Specialized Spray Sealants: Acrylic or polyurethane-based sprays are easy to apply and good for water resistance against rain or splashes. Multiple thin coats work best.
• Water-Based Coatings: For moisture mitigation in construction, two-component resin-based membrane-forming systems are specified to create continuous barriers. While not for small prints, this highlights the principle of using resins to block water vapor.

Important: Surface smoothing (like vapor polishing for ABS) can improve water resistance by melting the outer layer to fill gaps. However, research indicates that for some materials, this smoothing does not significantly reduce the material’s core permeability to water vapor. A true sealant coating is more reliable.

How Do I Design Parts to be Watertight?

Good design works hand-in-hand with material and process choices.

• Avoid Supports on Sealing Surfaces: If your part has a lid or a joint, design it so that critical sealing surfaces are printed cleanly, without support material scars.
• Incorporate Gaskets and O-Rings: For assemblies, design grooves for standard O-rings. Using silicone grease on the O-ring can improve the seal, though it won’t stop material absorption.
• Minimize Post-Processing Seams: Design parts to be printed in orientations that minimize the need to cut or drill, which can breach the sealed perimeter.

Real-World Applications and What to Use

How Can I Test My Waterproof Prints?

Before relying on a part, test it.

1. The Visual Leak Test: Submerge your part in water for several hours. Look for air bubbles escaping or water inside after drying.
2. The Paper Test: As done in formal studies, place dry paper inside a sealed part, submerge it, and check for wetness after a set time.
3. Pressure Testing (Advanced): For functional parts, gently pressurize the sealed object with air while submerged to identify very small leaks.

Industry Standards: For rigorous validation, industries refer to standards like ASTM D2247, which outlines practices for testing water resistance in 100% relative humidity environments. For coatings and sealants themselves, practices like ASTM F3010 govern the performance of two-component resin based membrane-forming systems designed for moisture mitigation.

So, is 3D printing waterproof? Not inherently—but it is highly water-resistable. The journey from a porous print to a sealed, reliable part is a matter of intentional choices. Start with a hydrophobic material like PP or PETG, reinforce it with dense slicer settings like high wall count and infill, and lock in the defense with a protective epoxy or spray sealant. By understanding the “why” behind the leaks and applying this layered strategy, you can confidently create 3D printed parts that stand up to rain, spills, and even full immersion, unlocking a world of practical and durable applications.

How to write a spec that gets priced correctly

A drawing is a contract. If it leaves a number open, the shop fills that number in with its own default. The default is rarely the one you had in mind. Put these five lines on every RFQ and most of the back-and-forth disappears before it starts.

• File format and units, with the model exported in millimetres
• Process and material grade, not a trade name
• Critical features and the tolerance each one needs
• Surface finish and the faces it applies to
• Quantity for the pilot build and for the year

The point is not paperwork. Each line removes a decision the shop would otherwise make for you. A complete RFQ comes back priced. An incomplete one comes back guessed.

What actually drives the price

Buyers usually push on material because it is the line they can see. In practice the material is rarely the biggest number on a quote. These five lines decide most of it:

• build volume and orientation
• layer height and support structure
• material grade and colour
• post-processing and hand finishing
• quantity per build plate

Ask for the quote split by line. A supplier who cannot break it down is guessing, and you will pay for the guess. The line you can usually renegotiate is the tolerance band, not the raw material.

Problems you will meet, and the fix

Every process has a failure mode it prefers. The same four show up again and again on this kind of work, and none of them are mysteries once you know what to look for.

• Warping on long flat faces where the part lifts off the plate
• Layer lines showing through a cosmetic surface
• Support scars on a mating face nobody flagged
• Dimensional drift on thin walls after cooling

Catch the fault on the first part, not the hundredth. A first-article check costs an hour. A bad batch costs the whole order. Write the check into the purchase order so nobody has to remember it.

What to check on the first article

The first article is the cheapest inspection you will ever buy. Use it properly and the rest of the run becomes boring, which is exactly what you want.

• Every dimension on the drawing, with the measured value written beside it.
• The material certificate, matched to the heat or lot number on the parts.
• The finish against the sample you approved, under the same light.
• Fit against the mating part, assembled rather than measured.
• Packaging, because parts that arrive damaged were never in tolerance.

Check in this order: datums, then mating features, then cosmetic faces. If the datums are wrong, every number after them is noise. Keep the report on file. When a problem shows up in month six, that document is the only thing that tells you what changed.

How to compare two quotes fairly

Two numbers are not comparable unless the scope matches. Line them up before you decide, because a low number with three gaps is not a low number.

Same drawing, same material, same finish, same inspection. Anything else is a different job wearing the same part number. Then look at what each quote leaves out. Freight, packaging, certificates and tooling are the usual gaps.

Ask each supplier to state their assumptions in writing. The one who does is usually the one who has run the process before.

Scaling from one part to a batch

The first part teaches you the process. The hundredth teaches you the process cost.

Watch three things as volume grows: setup amortisation, tool wear, and how much hand work the finish still needs. If the unit price barely moves between ten and a hundred, the cost sits in material or in hand work, not in setup. Ask which, because only one of them is negotiable.

Lead time behaves the same way. A one-off is scheduled around other jobs. A repeat order is scheduled around your forecast. Give the shop a forecast and the lead time gets shorter, not longer.

How to read a supplier's quote

A quote is a short document with a long shadow. Four things in it decide whether the job runs smoothly, and only one of them is the price.

• The scope line. It should name the process, the material and the finish, not just the part.
• The tolerance basis. General tolerance or the drawing, and which standard it follows.
• The exclusions. Tooling, freight, certificates and inspection are the usual omissions.
• The validity date. Material prices move, and an open-ended quote is a promise nobody can keep.

Read the exclusions before you read the total. A quote that leaves out tooling is not cheaper. It is a quote for a different job.

What to send with the first order

The first order sets the pattern for every order after it. Send a complete package once and the shop files it, and the second order takes a fraction of the time.

• A STEP or native model plus a PDF drawing carrying the same revision letter.
• The material callout by standard number, not by trade name.
• The finish and the exact faces it applies to.
• Any test the part must pass: fit, seal, drop, salt spray, dielectric.
• A contact who can answer a question inside one working day.

Then write down what was agreed. An email that confirms the material, the finish and the date is worth more than a longer purchase order that leaves them open.

When this is the wrong choice

A good supplier tells you when the process does not fit. These are the cases where we say so.

• The volume is so low that setup costs more than the parts are worth.
• The tolerance is tighter than the process can hold without a second operation.
• The geometry cannot be made without a tool feature that will not pay back.
• The material you need is not available in the form the process requires.
• The schedule is shorter than the tooling or setup time, and nobody has said so yet.

None of these are refusals. They are reasons to look at a different route, and the earlier that conversation happens the cheaper it is. The most expensive mistake in manufacturing is a process chosen before the question was understood.

Our solution for Make 3D Prints Waterproof

YiguProto runs 3D printing in house, from a single prototype to a production batch. We quote the process, the material and the finish as separate lines, so you can see where the money goes instead of arguing with one number.

Send a STEP file or a drawing and you get a DFM report in one to two business days. It flags the features that add cost and the features that will not hold tolerance on the process you picked.

Every order ships with an inspection report on the features you call out. If a part misses, we make it again. Ready to price a part? Start with a free quote and DFM review, or read more about our 3D printing. You can also talk to an engineer before you commit to a drawing.

FAQ about Make 3D Prints Waterproof

The short version

Make 3D Prints Waterproof rewards the buyer who reads the data sheet and the drawing together. Pick the option for the property that matters, not for the price per kilo.

Tighten only what mates. Test a sample before the run. Then let the process do the rest.