In a bathroom, everything is a drainage problem
A soap dish that holds water turns the soap into paste. A shower caddy that holds water grows pink biofilm in the corner within two weeks. A toothbrush holder with a solid base collects a centimetre of stale water under the brushes.
None of these are material failures. They are geometry failures, and they are decided in the first sketch.
Soap dishes: the slope is the product
| Parameter | Value that works | Failure if missed |
|---|---|---|
| Base slope toward drain | 3–6° | Flat base holds a film of water, soap dissolves |
| Drain slot area | 8–15% of base | Below 8%, water cannot leave fast enough |
| Slot width | 3–5 mm | Below 3 mm, soap residue clogs it |
| Rim height above soap | 8–12 mm | Lower, the bar slides out when wet |
| Foot clearance | 4–8 mm | Zero clearance traps water under the dish |
Two mounting families, with completely different quality risks:
Suction cup. Cheap, no tools, and the joint is the failure. A suction cup holds by vacuum, so the holding force depends on surface smoothness, not on cup size. Published pull-off values of 3–8 kg on glazed tile are realistic; on textured or matte tile the same cup holds almost nothing. Specify a pull-off test on the actual surface finish the buyer will use, held for 24 hours, and add a locking lever if the load is vertical.
Adhesive or screw mount. Adhesive pads (acrylic foam or silicone) hold well on clean, dry, non-porous surfaces but fail on damp walls and cannot be repositioned. Screw mounts are the only option for a tiled wall that gets soaked — and the only one that survives being knocked.
Shower caddies: two structures, two load paths
Tension pole caddy. The pole is compressed between floor and ceiling, and friction at the two ends carries the load. Practical limits: 5–10 kg total, pole diameter 20–25 mm, and a spring or threaded adjuster that can take up 30–50 mm of variation. The wall of the pole matters more than the diameter — a 22 mm pole with a 1.6 mm wall buckles before a 20 mm pole with a 2.2 mm wall.
Two specifications decide whether it stays up:
- End pad friction. Rubber or TPE pads, 60–70 Shore A, compressed against a dry surface. On a wet glossy tile the coefficient drops sharply — specify wet-condition testing, not dry.
- Shelf attachment. Clamp collars that rely on friction alone slide down over months. A collar with a mechanical stop, or a shelf that bears on a shoulder moulded into the pole, does not.
Hanging caddy. Hangs from the shower head, a rail, or a hook. Load is carried in bending by the hook, and the hook is where it fails. A PP hook creeps at 40–45 °C — which is exactly the temperature inside a shower — so a hook that holds 6 kg on day one may hold 3 kg after a month. Glass-filled PP or a metal core in the hook solves it.
| Element | Target | Note |
|---|---|---|
| Shelf load | 2–4 kg per shelf | Shampoo bottles are heavier than they look |
| Total load | 5–10 kg | Pole caddies, distributed |
| Drain slot area | 15–25% of shelf | Below 15%, bottles stand in water |
| Shelf lip height | 12–20 mm | Lower, bottles tip out |
| Rust-free claim | All-plastic or 304 stainless hardware | Zinc-plated screws rust in weeks |
Toothbrush holders: airflow and clearance
| Parameter | Typical | Why |
|---|---|---|
| Cup inner diameter | 60–75 mm | Holds 2–4 brushes without jamming |
| Cup depth | 70–90 mm | Brushes stand up; shallower, they fall out |
| Vent holes | 4–8 × 4–6 mm, at the base | No holes, water stands and the base stains |
| Compartment split | 2–4 slots | Separating brushes dries them faster |
| Removable cup | Preferred | The only way to actually clean it |
The most common design mistake is a solid base with a decorative pattern. Water enters along the brush handle, cannot leave, and the inside of the holder becomes the dirtiest surface in the bathroom. A removable inner cup, or a base with drain holes and feet, is the difference between a product that can be cleaned and one that cannot.
If the holder includes a toothbrush cap or a cover, check head clearance: electric brush heads are 15–20 mm thick and will not fit a holder designed around manual brushes.
Materials and finishes
PP is the default for wet areas: no rust, no plating, cheap, and it tolerates bathroom cleaners. ABS gives a harder, glossier surface and takes chrome plating well; unplated ABS yellows under UV from a window within a year or two. PS is cheaper and clearer but brittle — it cracks when dropped on tile, which is where bathroom products live.
Plating is the specification most often left vague. Ask for:
- Coating thickness: 8–15 µm for decorative chrome over ABS.
- Adhesion: cross-hatch or thermal cycle test, no blistering.
- Corrosion: 48 hours neutral salt spray (ASTM B117) with no white corrosion on the visible face.
A chrome-plated ABS soap dish that passes salt spray for 24 hours and fails at 48 is a normal outcome, and it is the difference between a product that looks new after a year and one that is peeling at the edges.
Mould and cleaning
Warm, wet, still water grows biofilm. Every design decision that removes standing water also removes the mould problem: slope, slots, feet, removable parts, and no enclosed cavities that cannot be reached with a brush.
Avoid deep narrow channels between moulded features. A 2 mm gap between two walls is exactly the geometry that cannot be cleaned and always turns dark.
RFQ checklist
- Mounting method and the wall surface it must hold on (glazed tile, matte tile, painted plaster).
- Required pull-off or load rating, tested wet rather than dry.
- Shelf load per tier, and total load for pole caddies.
- Pole length range and the ceiling height variation to be covered.
- Drain slot area target, and whether parts must be removable for cleaning.
- Material for each component, and the plating spec if any part is plated.
- Salt spray hours and the standard used.
- Hardware material — 304 stainless or plastic, never zinc-plated in a shower.
A bathroom accessory range is cheap to tool and cheap to ship, which makes it attractive — and it is also the category where a 2 mm geometry error generates the highest return rate, because the customer sees the failure every morning.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
