现在很多家庭都会购买大的纯净水桶，放在饮水机上使用，或者用来储存泉水，也有的会放在汽车上，以待远行时使用。
Now many families will buy large pure water buckets and use them in drinking fountains, or to store spring water, or some will put them on cars for use when traveling.
有一个不好的问题是，使用一段时间后，因为水垢，或者泉水里的泥沙累积，水桶会变脏。但纯净水桶的口都很小，手根本伸不进去，难以清洗，久而久之，水桶会越用越黑。
A bad problem is that after a period of use, because of scale, or the accumulation of sediment in the spring water, the bucket will become dirty. But the mouth of the pure water bucket is very small, and the hand can't reach in at all, so it's hard to clean. As time goes on, the more black the bucket will be.
其实有个简单的办法可以解决这个问题，就是用细沙。放入少量细沙和水，盖上桶盖，使劲摇晃，让细沙与桶内表面充分摩擦，五分钟左右，水桶就干净如新了。
In fact, a simple way to solve this problem is to use fine sand. Put in a small amount of fine sand and water, cover the end of the bucket, shake it vigorously, and let the fine sand fully rub against the inner surface of the bucket. In about five minutes, the bucket will be as clean as new.