Hot water bottles have been a household favorite for keeping warm and soothing aches for generations.
However, a new study from the University of Liverpool has found weaknesses in their design that could lead to unexpected bursts and burns.
Researchers from the university’s School of Engineering decided to investigate after reports of hot water bottles suddenly rupturing and causing injuries.
Despite their long history of use, little research had been done to understand how these bottles react to pressure and external forces.
In their study, published in Applied Sciences, the research team tested brand-new hot water bottles made from vulcanized rubber, a material known for its durability and heat resistance.
Each bottle was filled to about two-thirds of its capacity and then subjected to increasing pressure to see how well it could hold up.
Using real-world compression tests and advanced computer simulations, the researchers discovered that the neck and edges of the bottles were the most vulnerable areas.
These spots experienced the highest levels of stress, making them more likely to tear or burst under pressure.
To better understand why this happens, the team also cut test strips from the center of a hot water bottle and examined its mechanical properties.
They measured how well the material could stretch, resist breaking, and maintain its strength. The findings confirmed that stress concentrated around the bottle’s seams and cap, increasing the risk of sudden failure.
Dr. Ahmed Abass, a lecturer in Biomedical Engineering at the University of Liverpool, emphasized the importance of handling hot water bottles with care.
“Our study shows that placing too much weight on a filled hot water bottle—especially while sleeping—greatly increases the risk of rupture, which can cause serious burns,” he said.
For manufacturers, this research highlights the need to reinforce the neck and seam areas to make hot water bottles safer. Even everyday items like these require careful design to prevent accidents.
While hot water bottles remain a convenient way to stay warm, users should take precautions. Avoid sitting or lying directly on a filled bottle, and regularly check for signs of wear and tear. With better awareness and improved designs, hot water bottles can continue to be a safe and reliable comfort item for years to come.
