Background and objective: Lifelines in Iran, including the water supply, are not designed properly for coping with earthquake impacts. The history of these systems return back to about half a century ago, while the Lifeline Earthquake Engineering lasts no longer than about 3 decades. Therefore, lack of seismic design in water supply system of the country is inevitable. As a part of water supply system, buried pipes are vulnerable to ground motions, faults, passing through lands with landslide potentials and liquefactions. Based on this, it is necessary to forecast future performance of such structures during earthquakes occurrence. Tehran, as one of Iran's major cities, is located on an earthquake prone area with many active faults. Tehran 11 district is also very important district from exposure to earthquake hazards point of view. So, risk assessment and evaluating pipe lines performance in transforming and distributing water in the District 11 water supply network is of great importance.

Method: With utilization of attenuation relations and Hasus probibilistic hazard assessment method and by using programming VBA in Excel and utilization of GIS software, damages to the said water supply network will be assessed.  

Findings:The result shows that the there won't be many damages to the water supply network of District 11 of Tehran due to the Tehran north fault possible activities and only rigid pipes with small diameter will be damaged.   

Conclusion: Referring to the afore said network analysis which is done based on Tehran north fault activity, it is determined that flexible big size pipes and also pipes with the same quality connections bear less damages. Results of this research can be used for prioritization in line with retrofitting of Tehran District 11 water supply network.