Dihydrosphingosine 1-phosphate phosphatase required for efficient ceramide synthesis from exogenous sphingoid bases (PubMed:10477278, PubMed:10563329, PubMed:10856228, PubMed:9353337, PubMed:9419344). Involved in endocytosis and calcium-mediated signaling (PubMed:10856228). H2O + sphinganine 1-phosphate = phosphate + sphinganine Belongs to the type 2 lipid phosphate phosphatase family.