|1. A check valve must withstand for 1 minute, without leakage at joints or at the valve seat, an internal hydrostatic pressure of two times the rated working pressure of the valve. Slight weeping of water at the valve seat is acceptable for metal-to-metal seats. Leakage past clappers with, or in contact with, resilient seats, is not acceptable.
2. For the purposes of the test, “slight weeping” is defined as leakage not exceeding 1 fluid ounce per hour (0.008 mL/ sec) per inch (25.4 mm) of nominal valve size.
3. A Check valve must withstand for 16 hours, without leakage at the valve seat, an internal hydrostatic pressure equivalent to the head of a column of water 5 feet (1,5 m)high retained within the downstream portion of the valve body. No leakage may occur as evidence by wetting of paper placed beneath the valve assembly. This test is to be conducted with the valve in both the horizontal and vertical position if intended for such use.