“What Hydronics Taught Holohan” is Plumbing & Mechanical columnist Dan Holohan’s 374-page memoir, where he shares stories and knowledge he has gained throughout his career. It weaves technical tidbits with real-life examples and simple truths. He introduces interesting people he’s met and shares what he’s learned from them. The book covers a variety of topics ranging from the first time he saw square pipe to what he’s noticed most contractors have in common.