Elbow to P trap in Drainage System (Revit 2014)

We can convert the elbow to P trap direct with the process below:

1. Change the part type of P trap to elbow inside P trap family.

2. Load the family to your project.

3. draw pipe vertical and horizontal with elbow:

4. Change the elbow to P trap from type selector

It will be like this:

But be careful the way of drawing pipes, if you start from left to right it's totally different than right to left:

if you change the above elbows to P trap the shape will be like this:

Why this happen?

If you open the P trap family you will find two connectors, one of them is primary connection, mean this primary will connect first based on your path.

So if you start with path number 1 the primary connector must be on the top side of P trap:

and Path two the primary connection must be on side connection:

and to change the connector to be primary, select the connector then from ribbon and Re-assign it.

Finally I recommend to add two P trap to your project to select one of them during modeling.