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Managing Intersections & Pipe Connectivity

Contents

This article covers the ten commands used to connect, join, and snap pipes together, and to find and fix places where pipes cross or meet without actually being connected. That includes connecting loose pipe ends to a common node, joining two adjacent pipes into one, snapping pipe ends or grid points together, and the flag-based workflow for finding and breaking “unbroken” intersections — header/lateral crossings that look connected graphically but aren’t. Run these commands with care on imported data: a Fuzzy Tolerance set too large can snap pipe ends together that were never meant to touch, creating zero-length pipes.

Connect Pipe Ends

Connects a group of pipe features to a new common node.

  1. With a model open, the GDI Window displayed, and at least two pipes in the model, select Connect Pipe Ends from the GDI Command List.
  2. At the Select A Pipe Near The End To Move prompt, left-click each pipe end to connect. Right-click when finished; the selected pipes are highlighted.
  3. At the Location For The Common Node prompt, left-click the point where the new node should sit.
  4. If Prompt For Data During New Feature Entry is on, the new Node Data appears in the Data Panel — right-click to accept the defaults, or edit values and click Apply Data Values.
  5. If Automatically Update Pipe Length is off, respond to the message asking whether to update each pipe’s Hydraulic Length.
  6. The selected pipes are now connected at the common node.

Also runs by typing CONNECTPIPEENDS or CONNECT.

Join Adjacent Pipe Segments

Joins two adjacent, connected pipe features into one.

  1. Select Join Pipes from the Edit Graphics branch of the GDI Command Tree.
  2. At the Select First Pipe prompt, left-click the first pipe. It is highlighted.
  3. At the Select Second Pipe prompt, left-click an adjacent pipe.
  4. If an arc pipe was selected, respond Yes to convert it to a polyline pipe, or No to return to the prompt.
  5. If the common node connects more than two pipes, respond Yes to join anyway or No to return to the prompt.
  6. The two pipes are joined into one. If no other pipes remain connected to the common node, that node is deleted.

Also runs from the GDI Command List, or by typing JOINPIPE.

Notes

  • This command can join any two pipe hydraulic features, including compressors, fittings, regulators, valves, and wells; arc-type pipes must be converted to polyline first.
  • The joined pipe keeps the Hydraulic Type of the first pipe selected. If that type is “Pipe,” the result is a polyline pipe with a vertex at the former common node; otherwise the result keeps that Hydraulic Type, redrawn between the first pipe’s preserved From Node and the second pipe’s preserved To Node. Its Length equals the sum of both segments, and its other data comes from the first pipe. The second pipe’s record is then deleted.

Snap Loose Pipe Ends

Snaps together any pipe ends that fall within a User-specified Fuzzy Tolerance value.

  1. Select Snap Loose Pipe Ends from the GDI Command List.
  2. On the Fuzzy Tolerance screen, type a value and select a dimensional unit, then click Continue.
  3. Pipe ends within that radius are snapped together.
  4. If Automatically Update Pipe Length is off, respond to the message asking whether to update the affected pipes’ Hydraulic Length.
  5. A message may report the number of pipe ends changed. Click OK to clear it.

Runs by typing SNAPPIPES. Useful for correcting connectivity errors after importing data from external sources.

Notes

  • Take care not to set a Fuzzy Tolerance greater than or equal to the length of any pipe in the model — the routine will combine that pipe’s ends into a single node, creating a zero-length pipe.

Snap To A Grid Intersection

Toggles Grid Snap on or off, depending on its current status.

  1. With a model open and the GDI Window displayed, select Snap Grid Intersections from the GDI Command List.
  2. A message may report the current Grid Snap status. Click OK to clear it.

Runs by typing SNAPGRID.

Notes

  • Combine this with Set The Orthogonal Coordinates or Set The Orthogonal Coordinates – Plus to draw lines that snap to the Reference Grid; grid-snapping won’t work unless Display Reference Grid is also on, and turning Grid Snap on automatically enables that display option. Reference Grid spacing is set on the Graphics tab of Options & Settings.

Flag Unbroken Intersections

Finds and flags intersections where a lateral pipe is not actually connected to the header pipe it crosses.

  1. Select Flag Unbroken Intersections from the GDI Command List.
  2. On the Fuzzy Tolerance screen, type a value and select a dimensional unit, then click Continue.
  3. Respond to the message asking whether to enable the Allow Intersection Flag option for the found nodes.
  4. A message may report the number of unbroken intersections found. Click OK to clear it. The unbroken intersections are flagged.

Runs by typing FLAGUNBROKEN. Once flagged, run Break Flagged Intersections to break the unconnected pipes into two segments joined at the node.

Notes

  • This finds unconnected laterals off headers, unsnapped pipe ends, and sometimes redundant overlapping pipes — common after importing a DXF file whose long unbroken lines span several lateral intersections.
  • Unbroken intersections only occur at nodes; a crossing of two pipes is only flagged if a node falls within the Fuzzy Tolerance, which acts as a radius around each node.
  • Only pipes with an “Active” Facility Type are considered (set on the Facility Settings screen, Edit menu). Search times can be long on larger models — be patient.
  • The Allow Intersection Flag option this command can enable lives in the Graphic Data Items section of a node’s data.

Set An Intersection Flag

Turns the intersection flag display on for a selected node.

  1. Select Set Intersection Flag from the GDI Command List.
  2. At the Select Node To Flag prompt, left-click each node to flag. Right-click when finished.

Runs by typing SETINTERSECTIONFLAG or SETIFLAG. Use this to mark a header/lateral connection individually, rather than searching the whole model with Flag Unbroken Intersections.

Unset An Intersection Flag

Turns the intersection flag display off for a selected node.

  1. Select Unset Intersection Flag from the GDI Command List.
  2. At the Select Node To Clear prompt, left-click each flagged node to clear. Right-click when finished.
  3. The selected intersection flag(s) are removed.

Runs by typing UNSETINTERSECTIONFLAG or UNSETIFLAG. Use Clear Unbroken Intersection Flags to remove every flag in the model at once instead.

Clear Unbroken Intersection Flags

Clears every unbroken intersection flag from the GDI Display at once.

  1. Select Clear Unbroken Intersection Flags from the GDI Command List.
  2. Respond to the message asking whether to reset the Allow Intersection Flag option for the flagged nodes.
  3. All unbroken intersection flags are cleared from the model.

Runs by typing CLEARUNBROKEN. Use Unset An Intersection Flag to remove flags one at a time instead.

Notes

  • The Allow Intersection Flag option this command can reset lives in the Graphic Data Items section of a node’s data.

Break Flagged Intersections

Automatically breaks the pipes at every flagged unbroken intersection.

  1. With Flag Unbroken Intersections already run and at least one node flagged, select Break Flagged Intersections from the GDI Command List.
  2. On the Fuzzy Tolerance screen, type a value and select a dimensional unit, then click Continue.
  3. A message may report the number of flagged intersections broken and ask whether to clear the node flags; respond Yes to clear them or No to keep them displayed.
  4. If Yes, respond to the follow-up message asking whether to reset the Allow Intersection Flag option for the broken nodes.
  5. If No, a message reminds you to use Clear Unbroken Intersection Flags to remove the flags later. Click OK to clear it.

Runs by typing BREAKFLAGGED. An alternative is to break each intersection individually with Tap A Pipe.

Notes

  • Verify that the flagged intersections should actually be broken before running this — use Set An Intersection Flag and Unset An Intersection Flag to adjust which nodes are flagged first.
  • The Allow Intersection Flag option this command can reset lives in the Graphic Data Items section of a node’s data.

Delete The Pipe Crossing Markers

Removes all of the graphic markers placed by Find Pipe Crossings at each discovered crossing.

  1. With Find Pipe Crossings already run, select Delete Pipe Crossing Markers from the GDI Command List.
  2. Respond Yes to the confirmation message to delete all crossing markers, or No to end the command.
  3. A message may report when the process is complete. Click OK to clear it.

Runs by typing DELETECROSSINGS or DELXNG. Individual markers can also be deleted manually with Delete A User Graphic Symbol.

Notes & Considerations

  • Flagging an unbroken intersection, breaking it, and clearing its flag are separate steps: Flag Unbroken Intersections (or Set An Intersection Flag) marks a node, Break Flagged Intersections then actually splits the unconnected pipe there, and Clear Unbroken Intersection Flags (or Unset An Intersection Flag) removes the marker.
  • During feature-selection prompts, click a highlighted (selected) feature again to unselect it.
  • If Allow Undo Of Data/Graphic Changes is enabled (Utilities > Options & Settings > Environment), click the Undo icon to reverse the last data or graphic change.

See Also

  • Adding Pipes & Nodes
  • Editing Customer, Node & Pipe Data
  • Converting Features
  • Pipe Geometry: Adjust, Segment, Tap, Swap & Straighten
  • Deleting Graphics, Text, Tables & Views
  • Finding Locations, Text & Crossings
  • Coordinates, Projection & Snapping
  • Example: Selecting, Moving & Viewing Features
  • Example: GDI Coordinates, Commands & Grips
  • Example: Fittings, Panels & Palettes
  • GDI Utilities: Undo, Redo, Cancel & Housekeeping

FAQ

  • Why would I convert an arc pipe to a polyline pipe?

    Some GASWorkS editing tools can’t be used on arc-type pipes. Converting to a polyline pipe unlocks those commands while keeping the original shape — GASWorkS places a vertex at each degree of curvature along the arc and connects them with straight segments.

  • What’s the difference between converting one arc pipe and converting all of them?
    Convert An Arc Pipe To A Polyline Pipe lets you pick a single arc pipe to convert. Convert All Arc Pipes To Polyline Pipes runs the same conversion across every arc-type pipe in the model in one pass, and reports how many pipes were updated.
  • What kinds of background entities can be converted into a pipe feature?
    Only Arc, Line, and Polyline type entities — from either a DXF or a shapefile (SHP) background image. Other entity types in the background image can’t be converted directly to a pipe.
  • Do I need anything set up before I can convert DXF service lines to customers?
    Yes — the Facility Type you’re converting to must be set to “Active.” You can check or change that under Facility Settings in the Edit menu. You’ll also need a DXF background image with the service lines already attached.
  • What happens to the Color Legend when I convert it to User Text?
    It becomes a group of individual User Text features that you can manipulate with the standard User Text and Group commands, rather than the fixed Color Legend format. If a Color Legend Text already exists, you’ll be asked whether to delete it, keep it alongside the new one, or cancel.
  • I converted several DXF lines to pipes — why did it also ask me about node data?
    Converting a line can create new nodes at its endpoints. If the Prompt For Data During New Feature Entry option is turned on, GASWorkS shows the Node Data (and Pipe Data) for each new feature in the Data Panel so you can review or adjust the defaults before moving on.

Updated on July 29, 2026

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