Related על ברכות 49:25

[A person] should not spill water [with feces in it] in a place where he [wants to] pray [Shemoneh Esreh], but rather he should [spill it] four Amot away [from that place]. If [the feces have] dried up or reabsorbed (i.e. dissolved) then it is permitted [to pray Shmoneh Esreh next to them].