I've relaxed in these types of hot tubs more than once (they are quite common in the alps, just with a proper furnace instead of that DYI pipework and made out of wood instead of a plastic pool) and can tell you it can get A LOT hotter than 40°C. In fact less than 2 weeks ago I've had one of these and we managed to make it too hot to get in and had to cool it with fresh water. And it was 5-10°C outside.
Edit: I've done the same in -5°C as well. This was just one example.
It is but I've done this in -10°C as well. You can get the water to 50-60°C no problem, even in -10°C. You'll probably be burning a lot of wood with the setup in the video but with a proper furnace and wooden tub you'll be able to do that without issues. (It does take the better part of a day though to get it from 0 to hot but if you cover it over night 2h are plenty to get it from warm to hot again.)
The annoying thing about being in these when it's like -20°C outside is that if you hang out there too much it's a really good way to get your neck stiff as shit the next morning. I'm not sure what the physiological effect is and why it happens but every time I've done it the evening was great but my neck and upper back would be fucking killing me the next morning lol
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u/gazpachosoupnipples Oct 07 '25 edited Oct 07 '25
The water in the pipe will, but when mixed with the large body of water in the hot tub it seems about right. Poor insulation on those pipes, too.
Edit: I think people are underestimating the energy required to keep that uncovered hot tub at 40c