Sanitary Pipe Calculations and Venting

I wrote THIS POST years back regarding adding vent pipe to a sanitary system of pipe and fixtures. I'm happy to write that it's simpler now than then.

Just use an endcap family (made to look more like a vent cap) the vent pipe at the top and your fixture count should propagate all the way to the building connection as expected. That of course assumes you don't have open connections somewhere else along the way. The example above shows vent pipe using a separate type and a view Filter based on Type Name.

Use the Show Connections feature to identify them if any exist. I won't be shocked if you find some.

Fixture Units don't Update

I read a post at RFO that said the value for Fixture Units added up along a pipe run were correct at the pipe (in properties) but that tags attached to those pipes did not report a matching value. My first thought was that the system's Calculations parameter was assigned to something other than Flow. So I mocked up a quick test (using version 18.1.1.18 - 20170907_2315(x64) - 2018.1.1). Three families, two with the same Fixture Units assigned and one rogue.

I changed the middle fixture to be the same as the outer two and the pipe properties responded, the tag didn't (2nd from left). I took a look at the Calculations parameter for the Sanitary Piping System. This is using a stock Imperial Plumbing template. It's already set to Flow.

I switched it to None, clicked Apply, and the tags responded with this (Performance does the same).

I changed it back to Flow, clicked Apply, and the tags responded again but now they report the correct values.

I thought that there might have been a subtle change within the Mechanical and/or Piping settings that I missed when Revit 2018 arrived. I don't think there is though.

If you're counting on Fixture Units being added up and reported correctly in tags, you'll need to keep an eye on this. I've been able to wake up the tags by toggling between Calculation Settings for the Pipe System.

Added: Temporarily adding a pipe or altering the connected pipes also cause the tags to wake up. Also, just to make things stranger, changing the fixtures again I find the information displayed in properties of the pipe does not respond either, nor does a schedule of Pipes. However, if I have a Piping Systems schedule that does update as changes to fixtures are made.

Revit 2016 - Piping Units Addition

Plumbing engineers must feel a bit like Rodney Dangerfield's "I'm tellin' you, I don't get no respect!". Here's one for them, subtle though it may be. We can specify Liters per minute (L/min) for piping project units. (woot)

Revit MEP - Piping Offset from other Elements

When we sketch a wall we can provide an offset value on the Options Bar and then use the Space Bar to flip the side of the reference points we provide during sketching.

That flows pretty well (pun intended). It's not so fluid when using the Duct and Pipe tools. The Offset feature is hiding in the Justification Settings dialog AND the Space Bar concept doesn't work. We have to provide a negative value or be careful to start sketching in a specific direction to get the opposite offset.

This makes sketching pipe with a specific offset value relative to walls and other elements tedious. I think it is very likely (even much more so) to want to create pipe and duct taking into account adjacent elements like walls and structure AND provide an offset while doing so...it would be a lot more fun if there wasn't this extra little dialog hassle to do so.

Revit MEP Pipe Appearance in Sections

I met Freddie at the BIM Workshop in Anaheim recently. We chatted for awhile about Revit (shock I know) and then a little about music. It was great to meet someone who wasn't necessarily required to know Revit but decided he wanted to learn Revit and has become quite good at it. The company he works for (TJP Engineering) specializes in water treatment systems for aquatic attractions.

He passed along a graphic that Chris Aquino (Autodesk support specialist) marked up for him when he was trying to sort out piping graphics in section views. Sometimes writing this blog only requires sharing what other people tell me, thanks Freddie!

Here's the image which has markups that explain the various conditions they discussed.

Quick Summary of Issues:

• No rise/drop symbol? Most likely the pipe is sloping "through" the section.
• If you see a "crosshair" or "target" it is probably the pipe beyond the fitting but within the Far Clip Plane of the view.

Btw, my Uncle Ben called me Freddie when I was a kid. I. Don't. Know. Why... :)

Two Minutes with Rolling Offsets

Revit doesn't let us quickly create rolling offsets for piping or conduit, at least not in an uninterrupted process as we are sketching consecutive segments. In the past I wrote about a related concept called a Conduit Kick. It isn't that they don't want us to do it its just that Revit is biased toward creating vertical and horizontal runs. This means sketching a run of pipe and changing elevation usually creates something like this instead. The example on the left is good while the right is bad.

This video shows how to create a rolling offset for both pipe and conduit. The Routing Solutions tool works for pipe (and duct) but not conduit. We can also use the option Ignore Slope to Connect for pipe, duct and conduit. The resulting rolling offset does not abide by any rules for specific angles or slope. It's easy to create a sloping section between two elements as long as they are in the desired location, offset from one another correctly and at the elevations you need. The rolling offset just can't be created as we sketch from segment to segment. We need to place the two lateral runs and then return to create the rolling offset section.

Btw, there have been a few tweets on this subject focused on creating an app to help us cope with rolling offsets. Jeremy Tammik (The Building Coder) has written about it and wrapped up his posts with THIS ONE. Harry Mattison (Boost Your BIM) also inquired about it via Twitter but I don't think he's put anything to code about it yet.

Revit MEP Pipe Elevations

This is something I posted before but it is the second most viewed video I've done so here it is again.

Ever select a pipe and find different elevation offset values at either end? The culprit is different Level association at the fittings. Check the fittings at either end or along a connected run of pipe and you'll find a mismatch. Revit is just trying to keep the elevation the same even though the fitting elevation setting varies between them. Not too hard to fix but definitely going to confuse some new users.

One Minute with a Pipe Trap

Placing a pipe trap can be counter-intuitive or maybe just awkward until you "know how". The pipe trap family is built with the origin at the vertical or riser connection. That means you need to attach it to the bottom of a riser, the bottom of the pipe that is leaving a sink for example. Want to watch? It's just about a minute...

If you'd like to avoid placing pipe traps entirely you can consider incorporating them into plumbing fixture families that use them. Just do all the subtle plumbing work under the counter in the family and put the connectors at the wall face. I wrote a post that discusses the concept of rough-in families if you're interested. These are the links:

First mention of Rough-in Families
Follow Up Post

EdgeWise MEP for Revit

If you use Revit MEP and laser scan data then hopefully you've heard of ClearEdge3D and the new EdgeWise for Revit MEP? They recently announced that they're offering a software solution to bring 3D as-built models of pipes and other cylindrical MEP elements directly into Revit. It automatically extracts pipes, elbows and other features from point clouds and exports them to Revit as fully functional pipe objects. You begin by using their software to analyze point cloud data (the result of conducting laser/lidar scanning on-site). Once processed you can export this interpreted data to several software products including Revit MEP now.

If you are interested in a demo then check out when Beck Group’s Kelly Cone and Autodesk’s Kyle Bernhardt present it, via webinar, on Wednesday, September 26 at 1pm EDT. Beck Group was one of the early testers of the software and Kelly is quite fond of it. There will be a live demo of it too so you can see for yourself how much time it can save. Click here to sign up.

I received an email from them recently and I wrote back to ask a couple questions:

"Is the success of the export and functioning in Revit natively dependent on additional Revit families or based on the what is available in the stock content (US imperial for example)? I ask because I imagine there are elements that can be captured via a laser that your software can understand that might not have an equivalent Revit family element to use. What happens then?"

Christopher Scotton (President & CEO) responded with this:

"Thanks for Reaching out. The success of the import is not dependent on additional Revit families because Revit assigns the imported pipe objects to its stock pipe families, in this case Schedule 40 PVC along with the correct type diameter, elbow bend, etc. The centerlines come in as pipe placeholder. However, the accuracy and utility of the model is greatly enhanced by the use of custom families. In essence, EdgeWise imports cylindrical elements that are spatially accurate to the as-built conditions. Once in Revit, the elements need to be changed from the stock pipe family (if not Sch 40 PVC) to the correct pipe family.

Right now, EdgeWise MEP for Revit only extracts cylindrical features—pipes, round ducting, elbows and conduit—so we’ve not run across many elements that we extract that are not represented by a stock family type. But in those cases, Revit will place a PVC pipe and a placeholder that corresponds to the size, dimension and location of the unrecognized element."

If you are using point cloud data and Revit MEP (even if you use other software) you should check it out!

Revit MEP - Sanitary Venting and Fixture Units

Revit will push drainage/waste fixture units downstream to the end of the system. If three water closets are assigned four (4) waste fixture units each (WFC is the parameter in stock content), the pipes that are attached directly to each water closet will show four (4) WFC as a read only parameter value. As you check each pipe that is closer to the end of the system you'll find the fixture units incrementally increase after each water closet. If you assign the water closets to a sanitary system you'll see that they also add up in the System Browser (you can show Fixture Units). So far so good.

Venting is often required at each fixture and each vent is then routed over to the associated sanitary riser. This is where things go awry. The fixture units calculation inside Revit can tolerate a closed system where the contents of the pipe and the air in the vent can't circulate via a loop (see later images). As soon as you create a loop condition fixture units cease to accrue to piping layout.

Most of the engineers I've met want to use a fitting that has an integral vent connection. The one you see in the images in this post was created by Scott Johnson and he shared it with me a couple years ago and it works nicely. Attempting to simulate this isn't a problem until you try to connect them all together.

The solution in the images here involves placing a cap at the top of each Vent riser to close the system. To complete the venting (that isn't really venting anymore) you just run additional piping above the cap elevation. The different appearance for the vent pipe and fittings is done with a filter. The vent pipe you see is a separate Pipe Type so simpler fittings can be used as it is sketched. A Type Comment parameter value of "Vent" makes it easy to use a Filter. In plan views I'd be inclined to hide the vent pipe using the same Filter so they don't compete with the sanitary pipe graphics, the fittings above tend to obscure the fittings below. If you place these caps as high as possible it might not be necessary to fuss with a filter. This image shows the System Inspector results after using this technique.

System Inspector won't even work until you create a situation that doesn't allow for this loop. By loop I mean this condition.

I've experimented with changing the nature of the connector in the wye fitting itself but unfortunately as soon as Revit detects an alternative path that creates a loop, no fixture units past that point.

I suppose you could argue, "What's the point? Since you can't use the sizing tool on sanitary pipe anyway?". It might not really matter to some, but if the pipe knows what fixture units are present it should help you do the sizing in-canvas. It will help because you can touch a pipe and see the value (in the Properties Palette). You can then refer back to your cheat sheets to choose the best diameter for the pipe.

Made a video too, watch at OpEd Videos or You Tube or listen and watch here (my graphics card goes haywire at the end a bit).

Dept. of Subtle - Flipping a Fitting Replaces Other Fitting

This is a follow up to last Friday's post about sloping pipe. After using the Slope tool you might have noticed that a couple fittings were reversed. When I used the "flip arrow" to fix them I realized that another fitting nearby was affected too. A fitting getting flipped is effectively changing the slope of the pipe slightly because the origin of the fitting is altered slightly. The larger the fitting and the more eccentric the shape the more it can affect the piping. I created a second VIDEO to explain it further.

Dept. of Subtle - Sloping Pipe Creates New Pipe

I guess I've never paid close enough attention. When you use the Slope tool in Revit MEP the resulting sloped pipe is really new pipe. Revit recalculates what is necessary to create the slope and reassembles new pipe into the configuration.

I realized this when I was discussing a few options for displaying vent piping differently from the sanitary piping. One technique is to just use the Comment parameter (or some other custom one) to add a "vent" comment. A filter is used to isolate pipes, fittings and accessories that contain the criteria "vent". Pretty straight forward unless you decide to slope the pipe afterward. The sloped pipe loses the comment because it is new pipe and the code that rebuilds the pipe doesn't capture the Comment parameter value. I've posted a VIDEO to help explain this.

Revit MEP and CADworks - Online Presentation

I received an invitation to a presentation of the new piping productivity pack that CADworks has released. Here's a little bit of what the email said:

...snip
Today, CADworks® Content Management Service for Revit® MEP allows engineers to effectively achieve full participation in existing BIM promises by providing not only appropriate and quality Content, but the tools needed to sort out the new complexities of BIM. This solution offers a purpose-built Content Management Service for mechanical, electrical, and plumbing systems engineering.

CADworks Revit Piping Productivity Pack
This collection developed by CADworks of Pipe Types and Fittings, including Conduit Types, is now available for the extended MEP community for Revit MEP 2010 and 2011. These additions to our Comprehensive Content Suite greatly expand the power and capability of Revit MEP users.
...snip

They've got three dates listed and if none of them work for you then contact Bernie Duncan to see if they can set something else up for you. The three dates and times are:

• Tuesday, September 7, 2010 9:00 AM Central at: Register Now
• Thursday, September 9, 2010 Noon Central at: Register Now
• Friday, September 24, 2010 8:00 AM Central at: Register Now

If you are using Revit MEP you might want to check it out too? The first line says:

I am especially eager to introduce you to CADworks Revit MEP solutions that will make managing content and modeling Revit MEP piping systems much more enjoyable.

I know a couple people that wouldn't necessarily use the word enjoyable and piping at the same time, at times. It would be enjoyable to be able to use that word together with piping all the time. See what you think?

Revit MEP - Pipe Fittings and Angles

Piping often must be contorted a bit to deal with field conditions. Sometimes this means that a lateral run must rise to another elevation and shift aside to clear an obstacle. I'm not sure what is going on here but I thought it was an "interesting" field condition (in a parking garage during a recent hotel stay).

Doing so may mean that a fitting needs to rotate about the axis of the pipe run. Fittings rotate pretty easily in 90 degree increments just by clicking on the little circular rotate icon when the fitting is selected. Keep in mind that once you've connected pipes to the fitting that you'll likely lose the ability to rotate it with the little icon.When this doesn't cut it another tool might make the process a bit "easier". "Routing Solutions" exists to offer a variety of duct/pipe connection options by simply choosing two pipes or ducts. Revit will think about them for a moment and if possible offer you some choices. Like this image:

When you really need to rotate a fitting at a specific angle it gets a little "harder". You could rotate the fitting in a 3D view but making sure the origin of rotation is exactly aligned with the centerline of the pipe might be harder. The surest way is to cut a section next to the fitting temporarily so you can rotate it precisely. A bit more work but doable.

Once your fitting(s) is/are rotated then you can sketch a pipe between them in the same section view as long as you are careful to snap to the fitting connector at each fitting. The trim tool often does the job too, just get the pipes in the correct locations then trim/extend and let Revit put the fittings in.

Pipe Materials

A fairly common comment from someone using the Piping/Plumbing features in Revit MEP is, "Where is Cast Iron?" Fair enough! Where is it? It ain't there! Getting it there is a matter of editing the Pipe Sizes.xml file (default location: C:\Program Files\Revit MEP 2008\Program). At least that's true for past versions. The information is now embedded in Revit MEP 2009 and accessible from a dialog found under Settings menu > Mechanical Settings. This is the dialog you get:


You click on "Sizes" at the bottom left of the dialog and you get the information displayed on the right side. You can now add Material, Connection, Schedule/Type as well as Sizes. Using the check boxes offered, you can filter the list of sizes so only appropriate ones will be offered to you when you use specific types of pipe. You also use this to allow RME to use the size when calculating "sizing" for you.

Keep in mind that the Project Units of your project will affect the pipe sizes displayed on the Options Bar too. You adjust this via Settings menu > Project Units and then choose Piping for Discipline. Like this:


Similarly Wires Sizes and Duct Sizes are embedded within RME.