Looks like a great, simple, solution to me.
A few comments:
- Watch out for sags in the outside tubing that could hold water and then freeze.
- I wonder how much heat is lost in the tubing outside? I guess if you run it long enough, it will be fine. But too short of a run time will just circulate cool water. Some pipe insulation would help reduce this loss, but of course would make it more cumbersome to set up and store.
- I assume your tubing through the outside shower is snug enough that cold air won't leak in? Maybe a boot over it to protect from drafts?
- Is that the water heater access door that the tubing runs across? If so, watch it to make sure the tubing doesn't get too hot (and melt) from the exhaust. Maybe re-route or use some method of holding it away.
I look forward to hearing how well it works for you on your next cold weather adventure.
