If it does not drop but there is a small leakage at test cock No. 2, then No. 1 ball valve has a small leak, but No. 1 check valve is tight.

• 如果水柱没有下降，但是测试旋塞2号有点泄漏，则1号球阀有点泄漏，但是1号止回阀密封紧密。