Do hot water bottles have an expiry date?
Yes, classic rubber hot water bottles age. How to find the date of manufacture, when to replace yours and how to tell that a hot water bottle is past its best.
Most people don't know this: many rubber hot water bottles have a small flower or circle stamped into them. It isn't decoration, it's the date of manufacture. The year is usually in the middle, and the petals or segments show the month.
Why rubber ages at all
Every time you fill it, the rubber heats up, cools down again and gets bent and squeezed. Over time the material becomes brittle and fine cracks appear, often first at the neck and along the seams. You can't always see them straight away. It gets dangerous when a bottle full of hot water gives way just as it's lying on your stomach.
When should you replace it?
Many manufacturers recommend replacing a rubber hot water bottle after about two to three years, even if it still looks fine. Throw it out right away if you notice any of these signs:
- fine cracks or rough patches, especially at the neck
- a sticky or very hard surface
- the stopper no longer closes tightly or drips
- discolouration or a pungent smell
Hold the empty hot water bottle up to the light and stretch it slightly. If you see pale lines or hairline cracks, it's time for a new one.
Filling it properly if you stick with rubber
Don't use boiling water. Use hot tap water or water from the kettle that has cooled down a little. Only fill it about two-thirds full, squeeze out the air and screw the stopper on tightly. And always use a cover.
And without water?
The Vaermflasche is made of silicone and has a sealed filling. It heats up via a cable, you never pour in hot water, and there's no stopper that can come undone. It still feels heavy and soft, just like a real hot water bottle.
Never boil water again. Plug in, 3–6 minutes, warm. Up to 70 °C, no battery, 30 nights to try.
View