Figured it's time for a final update. Tub has been in use for 15 months now. 2 full summers and the seasons between.
In summary, I'm very pleased with how this project came out. The tub works great and is used daily when we're up there.
Random notes or observations:
- Controlling temperature isn't too to challenging once you've had a little practice with it. Taking the cover off does a surprisingly good job of lowering the temperature. You get a feel for how much wood in the boiler will result in how much temperature gain over how much time.
- If I open the damper more than 1/3 I risk having the water boil. Especially when the water is nearly up to temperature. Need to use caution to avoid having water boil in the boiler.
- While creosote and ash have accumulated, it doesn't seem to have affected the hot water output. I suspect I'm opening the damper a little more to offset for the lost efficiency. Not a big deal when I can't open the damper more than about 1/3 anyway.
- Tub and boiler survived -26*C (-15*F) overnight while full during our New Years trip.
- I've enjoyed the tub in temperatures as low as -18*C (0*F). It was heavenly.
- I bought a small 12V pump to help circulate the water faster so I could open the damper up all of the way without having the water start to boil. The results were disappointing. I used twice the wood I normally would have, but only managed to heat the water about 25% faster.
- We've worked out a bit of a system. I lite the boiler in the evening and will usually use the tub for an hour before going to bed. I throw an extra few logs in the boiler before bed to overheat the water a few degrees. My wife is an early riser and gets in the tub 1st thing in the morning, by morning the water has cooled back to normal temp. The boys like it a little cooler, so they use it throughout the day until I lite the boiler again the next evening.
- No problems with the water going foul. I throw in a tablespoon of "shock it" chlorine pool treatment when I fill the tub and we'll use it up to 5 days without a problem. Never once noticed any green water, kids haven't gotten rashes or ear infections, etc. Heard a theory that because the water gets so hot when it cycles through the boiler (output is often 200-210*F) the bacteria and algae killed in the process which makes a lot of sense.
- I'm now on my 5th spa thermometer. It's a harsher than normal environment and I keep buying the cheap ones. Spending the money on a good one will be cheaper in the end.