A bottle leaks at a joint, not through a wall, and the joints are a short list. Working through them before tooling is how a design avoids a leak that only appears once the lid is closed and the bottle is on its side in a bag.
The nine places it goes wrong
- Thread geometry. Threads that do not match between body and lid do not seal, however good the gasket.
- Gasket seating. A gasket that is not captured in a groove can roll out of position under pressure.
- Gasket material. Silicone and rubber behave differently with hot liquid and over time.
- Lid travel. A lid that bottoms out on the thread before it compresses the gasket has no seal at all.
- Venting. A sealed vessel with hot contents needs somewhere for pressure to go, or it pushes liquid out on opening.
- Spout closure. A flip or straw closure has its own seal, separate from the lid.
- Seam integrity. A body seam failure reads as a lid problem because that is where the liquid appears.
- Straw joints. Every push-fit joint in a straw assembly is a leak path.
- Pressure testing as delivered. Testing the body and then fitting a lid is not testing the product.
The order to solve them
| Stage | Settle |
|---|---|
| Before tooling | Thread geometry, gasket seating, lid travel |
| At first sample | Gasket material, venting behaviour, spout closure |
| Before approval | Full assembly test, filled, closed, inverted and left |
| At production | Assembly fit on every piece, alongside the vacuum test |
The test that catches most of it
Fill the finished, closed bottle, invert it and leave it. Then shake it, then leave it in a bag at an angle. It is unglamorous and it catches the failures a production line is least likely to find, because the line tests for vacuum and assembly rather than for a slow weep over an hour.
Questions buyers ask
Is a leak covered by the specification?
It should be. “Leakproof” without a test method and a duration is a description rather than a requirement.
Are screw lids or flip lids more reliable?
Screw closures have fewer moving seals. Flip and straw closures are more convenient and have more paths to fail, which is why the gasket is the part that decides.
Does a hot drink make leaking worse?
Yes — heat softens gaskets, raises pressure and makes a marginal design fail. Test hot as well as cold.
The fitments we offer are listed on the customisation page, and the assembly check is one of the eight control points.
