Abstract: To reduce the damage to a water supply system caused by negative water hammers that occur in its distributed pump group after power outage, a new joint protection scheme using a one-way tower and an air valve is described. The effect of one-way tower protection is clarified and a basic formula for setting the air valve in a main pipe concentration section is presented. This scheme is verified through numerical simulations in a case study of the urban water supply project in Tanzania. The results show that the protection by adopting both a one-way tower and an air valve is more effective than that adopting a one-way tower alone, and it reduces the project cost greatly. The diameters of the one-way tower and its connecting pipes should be optimized according to the conditions of a practical project.

Key words: complex water supply systems, distributed pump group, negative water hammer, one-way tower, air valve