It is "house and building technology". Haustechnik is a term which is quite old and concerned residential buildings with heating and sanitary installations. Nowadays the field and the "houses" got much larger and concerns air conditioning, fire-fighting equipment, building management an so on. Another german term is TGA which means "Technische Gebäude Ausrüstung" and still means house and building technology.
I would translate Pumpenauslegung with "pump selection" as the software helps you to choose the correct pump type and size. Pumpenauslegung does NOT concern "piping and connections"!! It has nothing to do with the piping, it only calculates the pump.

I only wanted to add a site for you, which should be helpful for your translation:http://www.glossar.de/glossar/z_cad.htm
It's the site for architects and builders with all the information on CAD and a very useful glossary with explanation of related terms. The difference between Haus- und Gebaeudetechnik is that the first one
concerns single family dwellings and the
second one multi family dwellings and commercial buildings. The CAD software
comes with different options and features. One is the
option/feature to draw an electrical plan, another is to draw the pipes for the plumbing take-of/plan.
Hope this helps,
Lis