There was a time when hot water bottles were in every household. Hot water bottles have moved on since the days where you would have to wrap up the hot water bottle in a towel to stop yourself being scalded. They now come in a variety of colours and with a variety of fluffy covers!
The point about hot water bottles is that they have to be hot. What most people do is literally boil water in a kettle and pour this moments later after the kettle has boiled, straight into the hot water bottle. This means that there is near boiling water in the hot water bottle and you can imagine what the risk then is if the hot water bottle bursts.
I have just settled a scalding claim for a client where the top of a flask which she had filled with hot water flew off. There appeared to be a defect in the lid. He sustained a scalding injury as a result.
Skin does not cope well with liquid above a certain temperature. This temperature is actually quite low and therefore even boiling water which has been left to cool for a while can potentially give rise to a scalding injury.
If a hot water bottle bursts and assuming that the hot water bottle has not been left lying in the drawer for 5 or 10 years where there is likely to be a degree of wear to the rubber, might give rise to a Product Liability Claim or indeed a claim against the shop where the burst hot water bottle was bought and under the Sale of Goods Act.
Evidence is vital which is why it is always helpful to keep receipts for as long as possible and obviously the hot water bottle must be kept as evidence.
I still wrap up my hot water bottle in a towel. At least the risk is reduced.