Troubleshooting - Water Module

This Tech Tip lists the common problems experienced using the Water Module and possible solutions.

Common problem during Analysis
  • Analysis terminates at the very beginning, with error messages, go to 1
  • Error checking displays a number of unconnected nodes, go to 2
  • Analysis terminates with the message "Can't solve", go to 3
  • Analysis run 300 iterations (max number), without reaching a solution, go to 4
  • Analysis successfully finished, with error or warning messages, go to 5
  • Analysis successfully finished, user is not happy with the results, go to 6
1. Analysis terminates at the very beginning, with error messages

Before the analysis, or if the User runs Error Checking

Analysis Menu › Error Checking

Only errors (or warnings) related to the geometry of the network can be detected, such as:
  • Nodes that are not connected to network
  • Pressure control that points to a non existing node, or level control that points to a non existing reservoir
  • Pipe with zero length or zero diameter
  • Valve and pump on the same pipe
  • Node without a demand pattern
Error messages are usually descriptive enough


It is possible to select the message in the Messages Window, and see the offending element by clicking the Show button, or press the Edit button to correct the problem.

2. Error checking displays a number of unconnected nodes

A node is connected to the network if it is hydraulically connected to some water source, reservoir or node with pre-set pressure.
  • Look for nodes that are obviously not connected (any pipes around?)
  • Look for missing pipe connections, go to 7
  • Look for nodes that are connected only to the reservoir inlet pipe (can't deliver water back)
  • Look for pipes with zero diameter
3. Analysis terminates with message "Can't solve"
  • Most probable cause is that some nodes have demands, without any possible source of water supply.
  • Pump switching off or control valve closing.
  • Reservoir inlet pipe can't supply water back into the network
  • If the problem cannot be solved, email project to support@knowbase.co.za
4. Analysis run 300 iterations, without reaching a solution
  • Problems with control valves, pumps or check valves changing condition all the time
  • This error should not occur, email project to support@knowbase.co.za
5. Analysis successfully finished, with error or warning messages

Some error or warning messages can be generated only during the analysis, or only when flows, pressures and other conditions in the network are known:
  • Error: Reservoir XX is empty, go to 7
  • Warning: Reservoir XX is overflowing, go to 8
  • Warning: Unbalanced flow of xx l/s in node XX Inflow into the node should be equal to outflow. Small differences can exist, subject to the accuracy of the analysis procedure. Usually, the offending node is not connected to the network.
  • Error: Insufficient inflow into pressure release chamber XX Outflow from pressure release chamber is determined from the demands and other conditions in the network, and is known. Flow control built into the chamber will restrict the inflow to the same value, if capacity of the incoming pipe is greater than what is necessary. If capacity of incoming pipe is not sufficient, an error message will be displayed. Try lowering the chamber if possible, or increase the size of the incoming pipe.
  • Error: Insufficient inflow into sump, pump station XX
  • Same as above, sump is practically a pressure release chamber attached to the pump station.
  • Warning: Pump is operating out of range, go to 9
  • Warning: Flow control valve XX couldn't be set to desired value
If this error occurs send project to support@knowbase.co.za

6. Analysis successfully finished, user is not happy with the results
  • Level control not working.
  • Level controls (valve, pump or reservoir inlet valve) should be all set a level (or water depth) inside the reservoir, and is not as an absolute elevation
  • Empty or overflowing reservoir, go to 7 or go to 8
  • Level in reservoir oscillates up and down in short intervals Decrease analysis interval from default value of 15 minutes to 5. If the reservoir size is to small, replace the reservoir with a pressure release chamber, or if there is a pump attached downstream, remove the reservoir and put in a sump at the pump station.
7. Empty reservoirs 
  • Look downstream for other reservoirs fed from this one. If they are overflowing, use level control, see 8
  • If the empty reservoir is pump fed, check if the pumps were running, set pump controls as necessary
  • If pump station is attached downstream, check pump controls, maybe the pump unnecessary takes water from the reservoir.
  • After you've done previous checks rerun the analysis and look at the reservoir graph. If the reservoir runs dry, and stays like that, supply is insufficient. Increase delivery pipe or pump size. If runs dry, but recovers, reservoir capacity is insufficient.
8. Overflowing reservoir 

Check upstream conditions.
  • If gravity fed, use inlet control valve to close the reservoir before overflowing.
Data Menu › Reservoir, select the Connections tab


Set Inlet Control to either modulating (set appropriate levels) or On/Off. NB: control works only on inlet pipe, select inlet pipe as necessary.
  • If fed by pump, set pump control on level in that reservoir.
  • Do not use both control simultaneously, because the pump can possibly run on a closed valve.
  • Do not set the top level exactly to maximum level, because of possible accuracy problems, set the level a bit lower.
9. Pump is operating out of range 

  • Check the direction of the pipe, maybe it pumps in the wrong direction. If necessary, go to Data Menu › Pipes


    and use the Change Direction option.
    • Check if pump runs against closed valve.
    • User selected wrong pump or pipe size.

    print print friendly version         


     
  • Knowledge Base OTHER TECH TIPS | CIVIL DESIGNER HOMEPAGE     

    CIVIL DESIGNER is a registered trade mark of Knowledge Base (Pty) Ltd, Developers of Professional Civil Engineering and CAD Design Solutions.