How to Build a DIY Fire-Heated Hot Tub (Because Science is Awesome!) So, you want a hot tub but don’t want to drop thousands of dollars on a fancy spa? No problem. With a little creativity, some copper tubing, and the undeniable power of physics, you can build your own fire-heated hot tub and soak in luxury—all without needing electricity or a pump. Step 1: Find a Tub (Or Repurpose Something Tub-Like) You need a container big enough to sit in comfortably. A repurposed livestock trough works grea