Hot water bottle alternatives

wort

I use microwave ones, they can get very hot and usually have a cover on them. Also I’ve got an electric back ‘brace’ that plugs in but can be left on as it straps around you . It was from lidl but sure you can buy anywhere

Floss

How long are you using your HWBs for, if they "always leak sooner or later"? The rubber perishes over time...

Nelliegrace

I have several vintage earthenware hot water bottles bought for about £5. I wrapped them in old towels and used them for the pets. I used them with cold water when the weather was too hot. I need to get plumbers rubber washers for them.

There are soapstones for heating, used wrapped in cloth like the old fashioned house brick which used to be stood by the stove.

A smooth stone could be heated in water, dried and wrapped. Stones can explode if they are heated on a fire.