Not the most detailed list of the Pipeline Contractors in Hawaii. The following list will however point you in the right direction. I do not guarantee that all numbers will work. I would recommend using Google as a great tool to find out more precise information on the Contractors listed below.
American Piping & Boiler Co
91-335 Kauhi Street # A, Kapolei, HI
Delta Construction Corp
91-255 Oihana Street, Kapolei, HI
Paul D. Maeda Inc
94-418 Papolohiwa Street, Mililani, HI
Wastewater & Pump Specialties
73-1220 Mahilani Drive, Kailua Kona, HI