A letter arrives from your city's water department. It mentions a backflow preventer, a deadline, and a certified tester. Most people have never given that device a thought, and now it has a due date.

Here is what it is, who can test it, and what to do before the deadline passes.

If you're building new or taking on a major remodel, most of the attention goes to the parts you'll actually see — the layout, the finishes, the fixtures. But long before any of that gets installed, there's a phase of the project that determines whether all of it works: the plumbing rough-in.