数学中有一类问题叫做水管问题. 编制问题的人认为进水管和出水管的流量分别都是恒定的. 真实情况并非如此. 本文用流体力学中的伯努利方程，计算出出水管的流量是随水池的水位变化的，并分别讨论了在进、出水管同时打开的条件 下，可以把水池注满水的条件，以及不能注满水的条件. 纠正了这类问题中的科学性错误.

There is a class of problems in mathematics called the problem of the water pipe. The flow rate of the inlet pipe and the drain pipe being constants are not the case. By using the Bernoulli equation in fluid mechanics，we calculate drainage pipe flow along the variation of the water level of the pool and discuss in the inlet and outlet pipe being opened at the same time the conditions，the pool filled with water，and can not be filled with water conditions. The scientific errors in this kind of problem are corrected.