Bentley Systems sells Haestad Methods' books for as much as US$195, but now they're giving them away -- sort of.
-- Stormwater Conveyance Modeling and Design (regularly $195)
-- Wastewater Collection System Modeling and Design (regularly $195)
-- Advanced Water Distribution Modeling and Management (regularly $145)
... now free, when you download them as chapter files in PDF format from here.