Plumb It, Don’t Plummet

February 22nd, 2013

It starts with a basic question: “Who owns the plumbing fixtures?”  The architect places the fixtures, but the engineer/designer specifies and plumbs the fixtures.  In a multi-model workflow process, should the fixtures be located in the plumbing model, the architectural model, or both?  If they are in both models, is the project fixture count accurate?  Is there a chance of the fixture count being doubled?  If the plumbing fixtures are copied into the plumbing model, what happens when there are background changes?  Can the architect rely on the plumber to maintain fixture locations, ADA clearances, and so on?   

After reading the first paragraph, many might think that the software’s Copy/Monitor functionality is the solution.  Copy/monitor is very useful with levels and gridlines, but maybe not so much with plumbing fixtures.  Copy/monitor will inform you of objects being changed and you will have the option to update them, but the occurrence of broken piping systems connected to those objects will not be revealed until the changes are accepted.

This article is intended to present an option for creating plumbing systems in Revit MEP in a multi-model workflow process without disrupting that process between the architect and the plumbing engineer/designer while maintaining the functionality of Revit MEP, BIM, and accuracy within the plumbing model. 

Before designing plumbing systems in a Revit model, a few plumbing basics need to be set up in the template.  Start by defining the pipe types: Black steel, Cast iron, Copper, PVC, and Standard are the basics.  Pipe fitting defaults are set at the pipe type (Type Properties in Revit MEP 2012 and Routing Preferences in Revit MEP 2013).  Set a preferred junction type (tee or tap) and then set the default fittings and pipe segment type. 

There are basic fitting types delivered with the software; however, additional pipe fitting types may need to be created or purchased.  Experience dictates that custom pipe fitting creation is best left to experienced individuals. 

Tip: It is beneficial to have an understanding of how to edit lookup tables (csv files) that are associated to the fittings to add various pipe size requirements. As you model your plumbing systems and “custom fittings” are being created by Revit accompanied with a “Warning,” be sure to address these warnings or the performance of your model will suffer.  Revit is telling you that the lookup table does not contain the fitting size being inserted into the pipe.  You need to decide if the lookup table needs to be edited—or perhaps hooking a ¼” pipe directly into a 12” pipe might not be the best routing solution.

Pipe systems need to be set up as well.  Create your pipe systems as needed if different graphic representation is required (system color, line weight, and line pattern are set at the system level).  Edit the Graphics Override and save them.



Tip: Revit contains default piping systems: Hydronic Return, Hydronic Supply, Sanitary, Vent, Domestic Hot Water, Domestic Cold Water, four different Fire Protection systems, and Other.  If you create new piping systems, make sure you duplicate the correct default system. For example, don’t duplicate Hydronic Supply to create a Hot Water Recirc system.  The default systems have an associated classification that can be used to set up filters to control what is displayed in your views. 

Tip: The “Other” classification will not calculate fixture units and should be used for systems such as fuel oil, medical gas, or natural gas.  For some reason, the “Vent” classification also will not calculate fixture units. 

View templates need to be created for graphic display of working views and views for sheets.   Consider creating filters associated with classifications as mentioned above to control the on/off display (turn off fire protection in a domestic water view).  The Medium or Coarse display setting will display pipe as single line and hidden line will display the rise/drop symbols correctly. The Fine display setting will display piping as double line.  Foundation plans look nice when displayed as double line. 

Tip: For linked models, it is beneficial to work with other disciplines and have them create views in their models for linked views needed in your model.  This saves a lot of time during model setup.  Return the favor by setting up views for others in your model.  You will be a hero!

Once the template basics are set up, it’s time to decide what to do with the plumbing fixtures (finally!).  My approach to this issue is to create families that will be located in the plumbing model and will sit right behind the plumbing fixtures displayed in the linked architectural model.  In actuality, these families represent the fixture carriers. 

Family creation can become very complex and frustrating.  The families for this solution contain very few graphics and require only a basic knowledge of family creation.  However, these families do contain multiple parameters that demonstrate the capabilities of BIM and can be created with minimal effort. 

I’ll use a custom lavatory family as an example. It contains only two extrusions for the hot water and cold water connections and a longer extrusion for the vent and waste connections.

Tip: A spacing of 7” between the extrusions will allow the rise/drop symbols enough room without overlapping in the medium and course view settings.  A parameter to adjust the height above finished floor after it is placed in the model should be considered as well (good for 3D views).

After the graphics are finished, attach pipe connectors to the ends of the extrusions making sure they attach to the correct face of the extrusion.



After the connectors have been placed, create parameters and assign to each connector.  Step one is to open the Family Category and Parameters dialog box and select Plumbing Fixtures.



Open the Family Types dialog box.  There are three parameters under the Mechanical group that are used to assign fixture units to the family. As mentioned above, there is not one for vent piping. 

There are shared parameters available for the four connection sizes used in this family (waste, vent, HW, and CW).  Insert them into the family from the Shared Parameter text file in the Family Types dialog box.  Select Add on the right-hand side of the dialog, then Select and insert the parameters.  You may need to browse to the shared parameter text file.

Going back to the Family Types dialog box, notice the four parameters under the Graphics group.  These are parameters that help control the size of the connectors.  Connector sizes are determined by their radius while pipe sizes are identified by their diameters.   Set the radius parameters to half the size of the associated connection size parameter in the formula column.   Use the radius parameter to control the connection size and extrusion size so they flex together.

This makes editing the family easier (if needed) by thinking in pipe diameter and letting the formulas do the math for you.

For the waste/vent extrusion, control the size by using the Waste Radius parameter. The vent connection will typically be smaller than the waste connection, so just assign the Vent Radius parameter to the vent connector.

Once those are added, the Family Types dialog box should start to look like the following figure.

Fill in the Identity Data fields as needed.  These will be useful in schedules.  Type Comments is what I use for Fixture Mark Numbers in my plumbing fixture tags.  Assembly Code is used for CObie requirements (if needed) and can be associated with specifications.  All of these parameters can be scheduled.

Back to the families….Select a connector and start assigning the attributes in the Properties dialog box.  Select the pull down for Flow Configuration and set it to Fixture Units.  Select the box to the right of the Fixture Unit field and assign the appropriate fixture unit type to it.  Set the Flow Direction to In for water and Out for waste.  Select a Loss Method and then System Classification. 



Once this is all set up, changing connection sizes in the Family Types dialog box should change the radius of the connectors and extrusions.  Fixture unit values are set in the Family Types dialog box as well. 

Tip:  For scheduling in Revit, consider creating a Total CW Demand Load parameter to help with sizing the water service to the building.  A parameter for assigning fixtures to stacks might be useful as well. 

One final consideration is to create several types in the family for each fixture type in your specifications.  Select the New button in the Family Types dialog box and create as many as you need. 

Tip: Name the type with the mark number that will be assigned to it.  Also, fill in the Description and the parameter that will be used to tag the family once it is inserted into the project.  Experience indicates that Type Comments parameter works well for tags (as mentioned above).

Once the basics are understood and a successful fixture has been created, start building all the fixtures you will need. 

Tip: Copy the lavatory fixture and rename it “Sink,” then edit the family, rename the types, edit the description, and save it.  Copy the lavatory fixture and rename it “Water Closet,” then edit the family and remove the HW connection.

For fixtures such as mop sinks and showers, add a dimension parameter that controls the offset of the waste connection from the wall and remove the vent connection. 



Create a family that contains only the waste and vent connections and extrusion.  Use this family for venting the waste up a wall from the mop sinks and showers.  Set the waste fixture units to “0” so the fixture unit count in the system still calculates correctly. 

Tip: Use a section view to connect the waste piping to the connectors.

Place the families behind the architectural fixtures.  The space bar will rotate the family to the correct orientation (CW connection on the right).  Piping can now be routed and connected to the plumbing fixtures.  By selecting the family, icons will appear that show each connection and the associated classification. 



If the waste or vent connection is selected for the first time, Revit will ask you what connection you want to hook to since the connections are stacked. 



After several fixtures are connected together, select a pipe and check the fixture unit count for a total.  If the total reads “0”, there is more than one open end somewhere in the system.  Check the pipe to the connectors or make sure the fixture units in the families aren’t set to “0”.

Other Tips

  • Open-end pipes will cause the fixture unit counts through the system to be “0”.  Cap the ends.
  • For loop systems, break the pipe and add caps to each side of the break.  Nudge them close together so the gap is not noticeable.   For single line plotting, create a pipe cap and remove the lines creating the schematic cap symbol from the family.  The result will look like a continuous line in the model.
  • Use caps when hot water lines turn into hot water recirculating lines.  Put a cap on the end of the hot water line so the fixture unit count calculates correctly.  Start the hot water recirculating line next to the cap and model the system.  This will allow the line patterns identifying HW and HWC to display correctly.

One final topic: Schedules.  Use them! The automatic schedules in Revit MEP are very powerful if you know how to use them.  Revit has a default plumbing schedule category.  Select it and start dragging parameters into the schedule.  All of the shared parameters mentioned above can be scheduled.  Figuring out how to filter and sort the fields in the schedule is challenging yet very rewarding once you have the final result achieved.  Schedules can calculate quantities and totals.  By simply placing our new plumbing carriers behind the fixtures displayed in the linked architectural mode, a total count of each fixture type and total fixture unit count can be calculated without even modeling a single pipe.  By adjusting the settings of the schedule, these totals can be calculated per floor, by waste stack, by fixture type, or the entire building.



In closing, remember these three things:

  • Communication is still the key to a successful project.
  • It flows downhill.
  • Payday is on Friday.

Happy plumbing!

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About the Authors

Dave Benscoter

Dave Benscoter

Dave Benscoter graduated from Northwest Missouri State University with a bachelor’s degree in Industrial Technology in 1988. He has been employed at HDR for nearly 25 years. During this time, Dave has worked for the Mechanical Department designing HVAC, Mechanical Piping, and Plumbing systems using multiple CAD packages (Revit MEP being the latest). He has been involved with the development, implementation, support, and content creation for these CAD packages while serving on the Best Practices team. You can contact him at [email protected]

 

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