I use CPAP and use distilled water to brew espresso as well. The panic buying of distilled water at the grocery story with each big weather event prompted me to look for a backup solution. So far, this machine seems to be doing a good job for me, after working a bit with the silicone seal (see below). The first couple of batches of water were a bit \"off\", smelling (maybe) of petroleum or something similar. After a good cleaning of the boiler tank, I took on the possibility of it coming from the silicone seal. I boiled a white vinegar and water solution in a pot and dropped the seal in there for a while. After that, i gave it a soak in a bowl of hot water and Dawn liquid. After a good rinse and reinstall of the seal, the next batch of water was clean and fresh. When it comes time to replace the seal, that will be my first step. I did see some comments here about a similar problem, so hopefully that helps someone. I would also suggest not allowing it to dry boil. The automatic shutoff seems to be a \"safety\", not necessarily something designed for regular use. With fill water at the \"full\" mark, set a timer for 3:20 or so and shut it off with some water still in the tank. You can then pour much of the mineral buildup down the drain, rather than building it all up on the stainless liner. I will be adding a countdown timer at the wall receptacle and all should be well.