Spanish to English Tech/Engineering Engineering (general) plumbing

This is an installation manual for a water cooler, I can't figure out what asparrago is, even with a diagram (and I can't put the diagram here to help), does anyone know? The translations I found in the glossary don't seem to work - they both contain the word stud, but this looks like part of a pipe connection (or perhaps the pipe itself)

Sujetar fuertemente con la rosca (7) por el espárrago inferior de conducción de agua.