When I was teaching Revit MEP to a Consultant in Iran they ask me about the Floor Heating System and they want to know how we can do this very fast in Revit , first of all I should say the piping shape for floor heating is various and in fact it’s depend to the Plan of the building.
but in many situation you need to create something like the title picture and this is very simple in Revit.
First step is about one Circulation of Pipe like the below picture. We need to the four edge for create this pipe system and as you see in the picture we have four pipe segments for four edges.
After you create the first loop of pipe now you need to select the fitting and delete it, because you should break the chain of the pipe at here.
After that you need to pay attention to the distance between parallel pipe like the below picture and run the Parallel Pipe Command from the System Ribbon.
Put the Dimension as you need for example 10 for Horizontal Number and 0.2 m for distance .
Put your courser over the one segment of pipe loop , as you see in the below picture and press TAB key from your keyboard for one time, you can see the guide line for duplicate of pipes.
Press Left click from your mouse and you can get the below picture.
The Final step is very simple , all thing you need is Trim to Corner command and you need to trim the pipe segments as I mark in the below picture on after the other .
Final Result is what you want and this method is very fast for modeling.