When you rant about how you hate smart phones!
I did leave you an out and suggested a digital spirit level.
Anyway had a look at some of those smart phone app’s and looking at pictures of the app some were reading say 3.6 degrees so they may go down to 0.1 degrees.
My smart phone is in a protective cover and would not sit level anyway. To remove it from the plastic spring loaded cover clips would soon cause the clips to fail.
The digital spirit level reading looked like they go to 0.01 degrees.
Yes the fridge is the important level Muzz, but even the fridge can handle a degree or two and as said the main level for the fridge is side to side as the refrigerant needs to gravity feed down the pipes and they do not have much of an incline on them.
I would think if you set up to allow the shower to drain properly it should be OK for the fridge unless you have TT’s problem.
I always use the same place to get my level and in fact as others do I have the spirit levels permanently mounted one on the draw bar and one specially set up at my air control station.
I don’t believe it is important to have an accurate reading but is important to always get a repeatable reading.
JR
