Hi, I'm Shawn and new to the forum. I've been a journeyman plumber since 1995 in Canada, and am still learning new things on a daily basis like everyone else. I just started teaching at a technical college, which is a beautiful thing. I've installed many boiler systems and of course they always get expansion tanks, but swear to God, I've never heard of using them in a domestic water system utilizing a hot water tank, electric or gas. They're not required in either the Canadian National or BC Plumbing codes. So what's up?