Let’s get this out of the way: “Shop-Vac” is a brand name, not a generic one. Just as we call adhesive bandages “Band-Aids,” we tend to refer to all wet/dry vacuums as “shop vacs.” No matter what you call it, a wet/dry vac is a darned useful addition to your home — as anyone who’s ever had an overflowing washer can attest. It’s also great for vacuuming up dry stuff, such as the sawdust and wood…