Revit MEP and Troublesome P-traps

This blog post was originally written for the Managed Design blog. Managed Design is now a U.S. CAD company, so please check back here at for more written articles from Philip Charlson and our new U.S. CAD Minnesota team.

Revit MEP has been around for quite a few years now, but Autodesk has still not discovered a great way to attach a P-trap to the different plumbing fixtures you want in your projects. If you have tried placing one of these P-traps, you find that it typically faces the wrong direction, and sometimes, doesn’t connect to a pipe at all.

I recently found an easier way to add these P-traps to your systems so that they display correctly when you create your plumbing isometrics. In the picture below, you will notice a typical issue when you connect your plumbing fixture to the waste line.

p trap issue pic 1
p trap issue pic 2

After loading the p-trap file you can access your Properties Palette, and within the palette, you will notice a parameter called Part Type. This will be listed as MultiPort. This enables it to be used in a number of locations, but typically for end conditions. Instead of keeping it set this way, we can set it to be a more specific component. In this case, we can set it as an Elbow. This will not change the look of your p-trap.

After making this change, I would suggest saving this p-trap in a company custom library for future releases, and sharing with your co-workers. You should also insert it into your company template for upcoming projects.

To start using the updated p-trap, locate elbows that have been placed within a project under your fixtures and select them. You can do a multi-select if you choose (don’t select all in the project though).

p trap issue pic 3

Within the Type Selector you will find all the other elbows along with the p-trap that you just modified. If you select the p-trap from the selector it will automatically replace the elbow in the project and orient it correctly without any hassle.

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Even though it isn’t quite an automatic setting to just simply sketch the piping and have it place the p-trap as you’re designing – it does beat having to place each one manually and orienting it correctly for every instance in your project. As a bonus your plumbing isometrics will come out looking correct as well.

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