negative pressures

[sekar utari]

Hi, can anybody help me. I have a final assignment project in my master program to evaluate Bandung City water supply distribution network. But now I really confuse, why there are a lot of negative pressures in this network?I was using reservoir node for water from spring, deep well, and water treatment plant. And this water supply system has differences duration in every area (e.g : there are areas that received water for 6 hours, there are also areas that received water for 12 hours). For this case, i was using "Controls" then "Simple" to state where and when the water flowing. Is there something wrong with my assumption for the model?Could anybody check what should I fix to avoid negative pressures?

*ps : I attached the file, thank you for your help.

[Patrick Moore]

Negative pressures occur when the hydraulic grade line (Head) falls below the elevation.  Head = pressure head + elevation Head.  In many cases this can occur when the head in a zone is "depressed" below it's normal values.  This can occur if a key supply fails to come on, or there is an open pipe between pressure zones causing a high water flow from the upper zone with higher head to the lower zone with lower head.  I suggest you look at the head values for junctions in a zone and compare them to what they should be and look for high flow pipes as a 1st blush check for what might be wrong.

Patrick Moore

On Thursday, January 7, 2016 at 8:51:31 AM UTC-7, sekar utari wrote: