The apartment has a tiny "just-in-time" hot water heater that seems prevalent in Brazil: a gas water heater with no apparent storage tank, and a flame that comes on (loudly!) whenever any hot water is drawn. This is in sharp contrast with the 30-ish gallon water storage tanks we have in the US, which keep a supply of hot water warm enough for a long shower or a load of clothes or dishes, but not continuously (it must have time to recycle). The difference between inline heat and stored heat led me to an interesting series of observations.
When I ran the hot water for the sink to wash my hands, the water was too hot, requiring me to add cold water to bring it to a safe temperature. But when I took a shower, it was never that hot! I couldn't get it as hot as the sink, which baffled me.
On a whim, I reduced the water flow in the shower, and waited 15 seconds, wondering if I was exceeding the capacity of the inline water heater. Sure enough, the water was too hot to touch. After a few more "change volume, wait 20 seconds, test temperature" cycles, I found that my preferred water temperature resulted from having only the hot water tap open, and about 70% of the way.
However, this now leads to counter-intuitive behavior during the shower. If the water is too cold, I reduce the hot water volume. If the water is too hot, I increase the hot water volume, and then stand aside for a moment until it cools.
I suspect I will be burned a few times when I return to my home this weekend, trying to unlearn my new habits.