Soap Dish: A 3D Printed Draining Tray for Bars of Soap, Kitchen Sinks, and Bathroom Counters

Best material for a soap-dish drain insert

Choose PETG for most household drain inserts and rigid soap trays. It is the practical first choice when the insert can be lifted out, rinsed, dried, and inspected. Choose an exact polypropylene grade when chemical exposure, repeated flexing, or low density actually matters enough to justify a harder print process. Keep TPU to a small, separately removable compliant feature. The material decision does not replace drainage geometry or a cleaning routine: a badly designed PETG insert can hold more residue than a well-designed insert made from another suitable polymer.

Why PETG is the household default

Prusa's current PETG guidance describes a tough, temperature-resistant material with low warping and good layer adhesion. Those are useful process traits for a thin removable insert with ribs, slots, and edges that will be handled often. They do not prove that every PETG print tolerates every bathroom cleaner or hot wash. Print a simple open shape, keep it removable, and test the exact cleaner and water temperature used in the home.

Do not solve a drainage problem with exposed infill, blind internal channels, or a hollow shell that can admit water through a seam and never dry. A solid-bottom tray needs an obvious outlet to the sink or a removable catch basin. If it only moves water under the soap and leaves the water trapped under the insert, it is a riser, not a draining design.

When polypropylene earns the harder workflow

Prusa's polypropylene guide highlights chemical resistance, fatigue resistance, low density, and moisture resistance, while also warning about strong warping, poor adhesion to common build sheets, and the need for a suitable printing surface. That makes PP a conditional choice, not an automatic upgrade. It can make sense for a thin snap-in insert or a deliberately flexible tab when the exact grade prints reliably and survives the actual soap and cleaner. It is unnecessary when a rigid removable PETG insert already drains, rinses, and dries well.

Do not transfer a chemical-resistance statement for a polymer family into a universal compatibility claim. Fragrances, oils, alkaline or acidic cleaners, disinfectants, pigments, fillers, and print defects can change the result. Test a coupon from the same spool and process before exposing the finished part repeatedly.

Use TPU as a separate compliant element

The current Prusament TPU 95A guide documents a specific flexible grade and its print requirements. That flexibility is useful for a replaceable foot or captured bumper that stops a rigid tray from sliding. It is less useful in the water-and-residue path, where flexible ribs and tight slots are harder to hold still while scrubbing and can keep surfaces touching after a rinse.

Make the TPU piece removable without tools, large enough to inspect, and mechanically captured instead of relying on an unknown adhesive around water. If the TPU becomes tacky, swollen, permanently compressed, cracked, discolored, or difficult to clean, replace it. For broader decisions about compliant parts, see when TPU belongs in a functional print.

Design the insert to drain, separate, and dry

• Give water a visible route out: slope ribs or channels toward an open edge, sink, or removable catch basin rather than a hidden pocket.
• Keep the insert removable: the user should be able to lift it out, reach every wet surface, and dry the tray underneath.
• Prefer broad openings and rounded roots: narrow slots, deep texture, decorative lattices, and sharp internal corners collect softened soap and resist a normal brush.
• Separate rigid and soft jobs: let PETG or qualified PP carry the bar and let a distinct TPU piece handle grip only where it is actually needed.
• Avoid false seals: do not describe ordinary FDM walls as watertight or leakproof without testing the finished part. A removable, open, drain-through design is easier to verify.
• Size for the real bar and sink: leave finger clearance, keep the bar stable as it gets smaller, and make sure runoff cannot reach a wall joint, wood edge, electrical item, or stored product.

The same separation-and-drainage logic applies to a sink-side sponge holder, but the loads and residue are not identical. Keep this page as the soap-dish canonical rather than assuming one generic wet-storage design fits every sink accessory.

Cleanability, moisture, skin contact, and contamination limits

A household soap dish should be treated as a washable organizer, not as hygiene equipment. Remove visible soap film and debris, rinse the part, let every surface dry, and clean the surface underneath it. Follow the soap maker's and cleaner maker's instructions, and test the exact printed material before repeated exposure. Do not assume a dishwasher, boiling water, bleach, alcohol, peroxide, or another disinfectant is suitable unless the exact grade and finished geometry have been validated for that condition.

The tray normally touches the bar, while skin contact is brief and indirect during handling. That does not justify a universal “skin-safe” claim for an unknown filament, pigment, additive package, nozzle history, or post-process. If the part is intended for prolonged skin contact, a clinical handwashing station, infection-control use, a shared institutional setting, or a formal contamination-control plan, use a purpose-made product or require documented evidence for the exact material and process.

Do not call an ordinary printed insert antimicrobial, sanitary, sterile, disinfectable, medical-grade, food-safe, or contamination-controlling based only on PETG, PP, or TPU in the product name. The linked material pages support print and engineering tradeoffs; they do not certify the finished soap dish for those claims.

A practical validation routine

1. Measure the full soap bar, the worn bar, the sink edge, faucet clearance, and the intended runoff path.
2. Rinse the empty insert and confirm water leaves every channel instead of pooling under a rib or foot.
3. Use the real soap for several wet-dry cycles. Lift the insert daily and inspect the underside, corners, seams, and any TPU interface.
4. Test the normal cleaner on a printed coupon from the same spool. Look for whitening, tackiness, swelling, cracking, odor retention, pigment transfer, or loss of stiffness.
5. Check stability with a new wet bar and a small slippery bar. The tray should not tip, skate toward the basin, or expose a sharp edge.
6. Retire the part if residue cannot be removed, water enters a hidden cavity, layers split, the surface becomes rough or tacky, a soft foot traps persistent moisture, or the tray no longer drains as designed.

If you want the featured model made, use the existing file-based quote route. For a different sink footprint, a two-material insert, or a cleaner-specific material decision, start with the material-before-quote checklist and send the soap type, cleaner, water temperature, bar size, drainage direction, contact requirements, and desired inspection or replacement interval to JC Print Farm.

Final recommendation

Print the removable rigid insert in PETG for a normal household soap dish. Move to an exact PP grade only when its chemical, fatigue, or flex benefits are needed and its print process has been qualified. Keep TPU to a separately removable foot or bumper. When the job carries a formal contact, disinfection, institutional, or contamination-control requirement, stop choosing by filament family and use a purpose-made product or a fully documented material-and-process specification.