很简单，删去while，so that引导目的状语从句。或者在while 前加 for a, 构成时间状语。

1 Customers can hold their bowls at the other end of the pipe so that they can receive the milk being poured by the milkman into it without any interaction between the two.

2 Customers can hold their bowls at the other end of the pipe for a while so that they can receive the milk being poured by the milkman into it without any interaction between the two.