A waterproof 3D-printed part is rarely chosen by material name alone. The best 3D printing material for waterproof performance depends on how long the part will be exposed to water, whether it must hold pressure, and whether the printed surface can be sealed or post-processed.

A plant pot, outdoor sensor enclosure, fluid manifold and submersible housing have very different requirements. Material selection sets the baseline, but print technology, wall design, orientation and finishing determine whether water eventually finds a path through the part.

What waterproof means in 3D printing

A part can be water-resistant without being waterproof. Water-resistant parts tolerate splashes, rain or short exposure. Waterproof parts prevent water from entering a protected cavity or passing through the wall during the intended service period.

For most 3D-printed polymers, the main risk is not water passing through solid plastic. It is leakage through layer boundaries, thin walls, seams, imperfect top surfaces or small gaps around threaded fittings. Porous print processes can also absorb moisture or create interconnected pathways that require sealing.

Define the operating condition before requesting production. Record whether the part faces intermittent rain, continuous immersion, internal fluid pressure, hot water, chemicals, UV exposure or repeated freeze-thaw cycles. A clear requirement avoids selecting a material that looks suitable on a sample but fails in service.

Best 3D printing material for waterproof applications

PETG for general-purpose enclosures and containers

PETG is often the most practical starting point for water-resistant and waterproof functional parts. It has good layer adhesion when printed correctly, low moisture absorption compared with nylon, and useful resistance to many household chemicals. It is suitable for housings, covers, brackets near wet environments, garden components and low-pressure liquid containers.

PETG also offers a balanced production profile. It is easier to print than many engineering polymers and is less brittle than standard PLA. For applications with moderate temperature exposure and no long-term outdoor UV requirement, it provides a sensible combination of cost, durability and sealing potential.

Its limits matter. PETG can soften under elevated heat, may creep under sustained load, and is not the first choice for parts exposed to intense sunlight for years. It should also not be assumed to be leak-proof at pressure without appropriate wall thickness, print settings and testing.

ASA for outdoor waterproof parts

ASA is a strong option when waterproof performance must continue outdoors. It has good weatherability and UV resistance, making it appropriate for external electrical enclosures, irrigation components, vehicle-mounted accessories and equipment covers exposed to Canadian seasons.

Like other filament-based materials, ASA relies on good interlayer bonding and controlled printing conditions. Its tendency to warp means process control is more demanding than PETG. When the application needs sun resistance, temperature tolerance and a stable outdoor finish, that added production discipline is usually justified.

ASA is generally preferable to PLA for exterior service. PLA may work for short-term prototypes, but heat, moisture cycling and sunlight can reduce its reliability over time.

Nylon for strength, with moisture controls

Nylon is valuable where a wet-environment part also needs toughness, wear resistance or fatigue performance. Examples include mechanical covers, clips, jigs and moving components that encounter water or washdown.

However, nylon is not automatically the best choice for a waterproof enclosure. Many nylon grades absorb moisture from the surrounding environment. This can change dimensions and mechanical behaviour, while some printing methods produce surfaces that require post-processing to become liquid-tight.

Use nylon when mechanical requirements lead the decision, then plan for sealing, conditioning and dimensional allowance. For a simple watertight box, PETG or ASA is often easier to specify and manufacture.

Resin for fine detail and smooth sealed surfaces

Stereolithography and other resin processes can produce highly detailed parts with smooth surfaces. This makes resin useful for small covers, laboratory fixtures, low-volume fluidic prototypes and parts where fine features affect sealing.

The resin formulation is critical. Standard resins may be brittle or degrade when exposed to UV, water, heat or specific chemicals. Tough, engineering or high-temperature resins can improve performance, but every formulation has different limits. Post-curing must be completed correctly, and hollow resin parts need well-designed drainage and cleaning to prevent trapped uncured resin from causing later failure.

Resin is best selected where accuracy and surface quality are primary requirements. For larger outdoor or impact-prone waterproof parts, PETG or ASA may offer a better service-life balance.

Material is only one part of the seal

A material selection cannot compensate for a poor design. In filament printing, specify sufficient perimeter walls rather than relying on infill to stop water. A thin shell with high infill can still leak along its outer layers. For many enclosures, multiple continuous walls and a meaningful top and bottom thickness provide a more dependable starting point than a single thin perimeter.

Part orientation also affects leakage. Position critical faces so they do not depend on a weak top-skin bridge or a complex support interface. Avoid placing a seal line across an area that will be heavily loaded, submerged or exposed to pressure. If a part has a lid, use a gasket groove, O-ring land or overlapping flange rather than expecting two flat printed faces to seal perfectly.

Threads deserve separate attention. Printed threads can work well for caps and service covers, but they should not be treated as pressure seals without an O-ring, gasket, tapered thread design or suitable sealant. Build in access for assembly and replacement of the sealing component.

When post-processing is required

For splash resistance, a well-produced PETG or ASA part may need no coating. For continuous immersion, pressure retention or porous print processes, post-processing is often the responsible choice.

Epoxy coating can seal layer lines and internal surfaces, although it changes dimensions and may not suit tight tolerances. Vapour smoothing, where compatible with the selected material and process, can reduce surface porosity. Chemical sealing systems may also be appropriate for production components, provided their temperature, chemical and food-contact status matches the application.

Do not apply a coating as an afterthought. Include it in the specification because it affects threads, mating surfaces, hole sizes, finish expectations and lead time. If the part will contain potable water, food, medical fluids or aggressive chemicals, confirm the material and finishing system against the relevant compliance requirements before production.

A practical specification for waterproof parts

A complete order brief should state the material, intended water exposure, required temperature range and whether the part is exposed to UV. It should also identify pressure conditions, critical sealing surfaces, mating hardware, post-processing needs and any required testing.

For example, “PETG enclosure for intermittent outdoor rain” is a useful starting point. “ASA enclosure for year-round outdoor use, gasketed lid, M4 inserts, no internal water ingress after a defined spray test” is a production-ready requirement. The second description gives the manufacturing team a basis for selecting orientation, wall strategy, finishing and inspection.

If the part protects electronics, specify the enclosure target separately from the plastic material. An ingress-protection requirement, for example, depends on the full assembly: cable glands, fasteners, gaskets, joints and test method. A waterproof printed housing can still fail through an unsealed connector.

Test the actual part, not just the material

Testing should match the risk. A rain-exposed cover may only need a controlled spray test and visual inspection. A container can be filled and left for a defined period over absorbent paper. A pressurized component requires a more formal test method, controlled pressure and appropriate safety measures.

Test more than one sample when the part is critical. Print variation, orientation and finishing can change results. Record the material, machine process, wall settings, finish and test outcome so a successful configuration can be repeated for future orders.

For most non-pressurized applications, PETG is the efficient first choice. Move to ASA when outdoor durability matters, use nylon when mechanical performance justifies moisture management, and select engineering resin when detail and surface quality lead the requirement. The dependable result comes from treating waterproofing as an ordered system of material, geometry, production settings, finishing and verification.