Looking for CAD symbol source

Gooserider

I am working on laying out a proposed heating system setup for my house, and am running into one minor problem that I'm hoping someone can point me at a solution for...

I am using QCAD, a low cost, general purpose CAD program that runs on Linux (and that other O/S). QCAD uses the same .dxf format files as AutoCAD, and while it comes with a pretty good library of pre-defined objects, it does not have any of the various plumbing and hardware stuff that one uses in a hydronic system (i.e. circs, the different valves, etc...)

I can make my own set of images by tracing the bitmap graphics that I find in various company tech references and the like, but this is really a painful thing to go through. I'm willing to lay odds that the .dxf image library I need probably already exists somewhere, but I haven't been able to find it...

Can anyone point me to a (preferably free) source for this sort of .dxf format image file library?

Thanks
Gooserider