Water age analysis - Time Step

[mduran]

I am running a water age analysis on a model of 4,000 junctions, two storage tanks and five reservoirs. The hydraulic time step is one hour and the quality time step is 1/10th of an hour (6min-following the recommendation of the software vendor). The problem is that when I modify the hydraulic or the quality time step, the water age results change significantly.

I want to know how to determine the appropriate time step in this or any case, a time step that will give me a stable hydraulic solution. I am concern that the software does not give error messages/warnings when the time step is not short enough to find a solution in all the pipes or reservoirs (for the water age analysis).

Any advice or comment on this will be highly appreciated.