Some time has past since my last post about hot tub.
Must admit that you have to have + degrees outside before you try filling hot tub. I was lazy enough to play up to 3 days trying to get hot tub planks to suck the water in and those 30 min. leak seams to be lie anyway. I used silicone where side planks meet the floor panel and (not in side of side plank cuts but just inner corner of hot tub). This was done because of crappy pump i mentioned (btw: pump seams to be dead for now) so I could fill the hot tub quicker and planks would “auto” expand. As you can see we made some benches as well.
After 3 day play (refilling, refilling) the hot tub has been holding water for more than 2 weeks and water level has dropped only for about 5cm (mostly because evaporation). I had only one test run and I got water temperature from +7′C to 25′C in about 7-8 hours. Not enough and I think I know the reason as well. Stove needs to be lower, so that the cold water (lower pipe) would be on same level on both sides. Also if possible you and I should use bricks to cover stove so that the heat and energy would not scatter so quickly.
And the ladder made from left overs.
A tip: When firing the stove you should cover hot tub from top and keep mixing the water. It heats up quicker this way.
Interesting note: On first test round I did not add any more wood after 22:00 and water at that time was 25′C. Next day around 11:00 water had still +22′C (air temperature at that night was aprox. 4-6′C only.