This Heatwave Hot Water Bottle Hack Is Doing The Rounds – With A Warning
So, if you do want to use this hack, make sure to fill the hot water bottle to the middle rather than the top. Alternatively, if you have two hot water bottles in the cupboard, use one solely for cold water and the other for hot.
Article source: https://www.huffingtonpost.co.uk/entry/heatwave-hot-water-bottle-hack-warning_uk_62d665abe4b008a2d03df53e