The essential thing to remember about pitot tubes (for air speed indication and static systems for altitude indication) is that air does not 'flow' through them, a pitot system is closed at the instrument end. It works because of an increase in pressure as your aviation machine flies through the air. Hence, as in any fluid pressure system, the effect of right angle bends is negligible and the system is calibrated as a whole using varying types of 'puffer box' to simulate altitude and speed by varying pressure in the system, +ve px for the pitot side and -ve pressure for the static (except maybe if you operate out of Denver). As Andycirl says the probe needs to be in an undisturbed airflow mainly to prevent fluctuation on the instruments. As for water traps they do what they name indicates, preventing water getting too far into the system and potentially freezing, thus giving erroneous indications. There is normally a requirement in a maintenance schedule to drain them at regular intervals.