Is it permissible to act upon the principle that the ritual impurity of the street is excused, whether it be extensive or slight, in order to avoid hardship, and is it true that one is not required to investigate the presence of impurity or its dryness when in doubt about the impurity of footwear?

The rule regarding sewage water and mud is sound, provided two conditions are met: the impurity is not predominant over the water or mud, and the worshiper is not certain that the impurity itself has touched his garment or shoe. There is no need to search or investigate whether the shoe has been soiled by impurity, because the default state is purity. It is advisable to ignore obsessive thoughts (waswas) and stay away from their causes.