Select samples from the finished products of pipes, fittings, and valves made from same lot of raw material, dosage and production procedure as a group, For DN?30mm,the sampling quantity of each group should contain not over 20,000 pcs, for DN＞32mm, the sampling quantity of each group should be not over 5,000 pcs. If the finished product quantity is insufficient in one group after 7 days production, set it as a group. Inspecting the appearance and dimension conforming to GB/T2828 sampling standard, select sufficient quantity (not less than 10pcs per batch) of samples for undertaking the inspection on appearance and dimension and to proceed all of the above-mentioned performance test and characteristics.