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Drainage pumps commonly used in buildings include submersible sewage pumps, submersible drainage pumps, vertical sewage pumps, and horizontal sewage pumps. Due to the limited space typically found in building sites and the relatively small flow requirements, submersible sewage pumps and submersible drainage pumps are often preferred. Submersible sewage pumps are usually installed in critical areas, while vertical and horizontal sewage pumps require more space for installation, as well as considerations for earthquake resistance, self-priming, and layout. Therefore, they are less frequently used in typical building applications.
When selecting the flow rate of a drainage pump, it should be based on the design second flow for domestic drainage. If the flow needs to be adjusted, the maximum hourly drainage flow should be considered. For fire elevator pit drainage pumps, the flow rate must not be less than 10 L/s. The head of the drainage pump is determined by the lifting height and pipe losses, with an additional free head added. This free head should be between 0.02 and 0.03 MPa. The flow velocity in the suction and discharge pipes should not be less than 0.7 m/s or exceed 2.0 m/s.
In public buildings, a backup pump should be provided for each individual drainage tank, and these pumps should typically operate in an alternating manner. In basements, equipment rooms, and garages, if there are two or more drainage pumps, a backup pump should be installed. If an emergency drainage system cannot be set up, the pump should have an uninterrupted power supply. However, if the drainage pipe can be closed, an uninterrupted power supply may not be required, but an alarm system should still be in place.
When handling sewage or wastewater containing large debris, the outlet pipes from submersible sewage pumps in different sumps should not be merged. However, when dealing with general wastewater, the discharge pipes from submersible sewage pumps in different sumps can be combined based on actual conditions. When two or more pumps share a single discharge pipe, each pump’s discharge line should be equipped with a valve and a check valve. A check valve should also be installed if backflow is possible during single-pump operation.
It is not allowed to merge pressure drainage systems with gravity drainage pipes. When submersible sewage pumps are handling large debris, a grinding device should be installed. For wastewater containing fibrous materials, larger submersible sewage pumps are recommended. If the motor power of a submersible sewage pump is 7.5 kW or higher, or the outlet diameter is DN100 or larger, a fixed auto-coupling device should be used. For smaller motors or smaller outlet diameters, a mobile installation method is acceptable.
For submersible sewage pumps used in sewage collection pits, a fixed auto-coupling device should be installed to facilitate maintenance. Drainage pumps should be capable of automatic start/stop and on-site manual control. Multiple pumps can be operated in parallel or staged according to demand, ensuring efficient and reliable performance under varying conditions.
October 01, 2025