rotaryguy,
from api-610, 10th ed:
"4.2.14 Pump type VS3
Wet pit, vertically suspended, single-casing axial-flow pumps with discharge through the column shall be designated pump type VS3.
4.2.15 Pump type VS4
Vertically suspended, single-casing volute line-shaft driven sump pumps shall be designated pump type VS4.
"
good luck!
-pmover