Problem

After computing a model, the following user notification for a pump is generated:

Reference to a deleted or inactive downstream pipe

Solution

This error is generated with the downstream pipe of a pump is incorrect or missing. To resolve this issue, double-click on the pump to open the Properties dialog. Find the item "Downstream pipe". If it says None, or if it displays a deleted or inactive pipe, you will need to change this to a valid pipe in the model. 

See Also

Node is not connected to, or is isolated from, a boundary (reservoir or tank) user notification

How do you change the direction of the downstream pipe for valves and pumps?