Although our LDPE plastic inner tubs can withstand the frost, the stove itself and any passages to your filter or to the stove most vulnerable. In particular, the outdoor stove has a double wall where there is water. This could cause damage if the water freezes. An intermediate solution could be to place shut-off valves between the tub and the stove. This allows you to leave the water in the bath, but drain the outdoor heater separately.
For those who definitely want to leave the water in the bath, we can also offer an electric spiral heating of 3000 Watt. You can place this on the return of your filter installation or a separate circulation pump. Do not expect miracles from this, but it can at least keep the bath free of frost. To do this, the filter pump has to run 24 hours a day.