Here in the UK it's been a great summer and I thought it would be good to relax at the end of the day in a nice hot tub. Trouble is they are quite expensive to buy and run and you need power and chemicals and really how many times would you use one. So I decided to build a low cost hot tub which can be run off grid and can be used quick and cheaply to have some fun.
Step 1: Materials
Knodd 40L bin with lid from your favourite Swedish bin emporium. £15 25 m 10mm micro bore central heating pipe from any plumbers merchants. £ 40 Kids paddling pool - I got a 1.9 m pool from Argos at the end of the season for £30 Aquarium 8mm tubing for pumping the water round your coil. 12v pond or bilge pump to circulate water. 12v power source - a car battery is ideal .
Step 2: Construction
The beauty of this is that it is so easy to make. We only need to construct our heat exchanger inside the metal bin in order to get tubbing!
If you go with the Knodd bin you will see that it is tapered. This allows us to use it as a nice former for our heat exchanger.
Start by drilling a hole in the side of the bin and insert the end of the coil from outside to inside the bin. Then start turning the bin smoothing the coil tight against the outside of the bin.
After a while you will have a lovely shiny heating coil.