A good building/house drainage system requires certain essential features to function efficiently. The pipes must be made of nonabsorbent materials to prevent leakage and contamination. Traps are necessary at various points to prevent sewer gases from entering the building and to maintain a water seal. However, branch drains should be kept as short as possible to minimize potential blockages and ensure a quick and efficient drainage flow. Therefore, the correct statements are that pipes should be nonabsorbent and the system should include necessary traps. The third statement about branch drains being long is incorrect.