Recycling: Hot water bottle sealing

We recently had a hot water bottle, which no longer served it’s duty. How can a hot water bottle can no longer work? The seal on the cap wears out. The hot water bottle drips when you fill it with water.

Another small plastic part, which leads to the unusability of the whole object. For us, an object does not end up in the trash because of such small parts. It’s time to get down to business.


The part that is worn is the black part. This is made of a flexible plastic, so that no water can escape between the cap and the bottle. Over the years, the part has partially melted and become brittle.


A few subtleties always require several attempts. But the basic modeling went relatively quickly. Here you can see the new spare part in its full glory.

A flexible filament is needed. I have white TPU filament lying around at home, I used that for this.


Here is also a print. The new replacement part is not 100% in the same shape as the original part. I can’t make out the exact shape because of the derformation. But it still appears to be functional. The replacement part fits on the cap of the bottle.

However, in a test with water, the bottle continued to drip when pressed firmly. After a few tests, it turned out that the walls of the part were too thin, because I had printed that with 10% filling. With a 100% filling has shown that no more water goes through there.


The new part fits perfectly on the mold and keeps the bottle from dripping. So the hot water bottle is functional again. I made some minor improvements and uploaded the result including the source code on Thingiverse.