Water bed kiln to supplement inflatable hot tub inflatable spa roast? Just got one of those inflatable spa / inflatable hot tubs. ...

Just got one of those inflatable spa / inflatable hot tubs. It works pretty all right, I was surprised, but the wet temperature is a moment or two week. Anyone think a waterbed boiler might help it get optimal temperature? The spa walls are made of a vinyl product.
Answers:    Unfortunately you basically found out why they are cheaper. The heaters are 115v and can only sort the temp go up around 1.5 degree an hour. The nice thing is that they are cheap to operate beside the coil heater around the pump. The glum part is that they are expensive to fix and near isn't any way to suppliment the warmness. I have played around next to some of our soft tub customers for years. I don't think much of the product. Wish i could comfort you. Be careful and do not permit any type of immersion heater if you jump that route neary the walls or you can melt them.
Take a look at the wattage rating on the spa kiln, and that on the waterbed heater. If the waterbed electric fire is very small compared to the spa stove, it more than likely will do little to put on a pedestal the temperature.

Also the heat control on the waterbed heater may not shift as high as you want the river temperature.

Maybe a cover over the spa while it is heat will help.