Warbie, are you a P.E. and just need to do diagramatic stuff or do you need to get into more rigorous detail?
If you're doing diagramatic work, you can try Randy Wilkinson for a quick download of his stuff -
www.hvacware.net.
If, on the other hand, you need to do commercial/industrial detailing (as I do) you really need to be running a commercial package, a few I have used are:
Quickpen, CadPipe, Intelicad and SPD. Most of those are relatively 'high-end' packages, even by Autodesk standards (some are 24k a seat).
As for automation, what is it you need to automate?
Just drawings? Plasma shear? Automating takoffs? Spooling pipe? 3D? Walkarounds? Renderings?
All of the above do that and more. Autoroute, collision-check, takeoffs, 2D/3D (mixed as well) and some can run a plama shear directly, spool pipe, do flanges, tanks, pumps and section duct.
You might go to
www.intelicad.com and see if you can get in touch with Matt Milner for a working demo (again, if you need to do detailing).
You might also try CadDuct or maybe MechQ (both do piping as well), I think they may be a little more reasonable (especially MechQ).
Tony