Every year my rental house is inspected by the city. Last time the inspector told me to add a backflow preventer (one-way check valve) to the handheld showerhead in the bathroom. The showerhead is on a long enough hose that it could be submerged underwater in the bathtub, and this would prevent drawing tubwater back into the water supply. (That bit seems a little hypothetical to me, but no matter.)
My problem is I can't figure out where to get one. The home centers only have garden hose backflow preventers, and nobody there has heard of one for a showerhead. I suppose I could call a plumber, but that would cost me a housecall, and I'd rather just install it myself.
Best Answer
They're also known as vacuum breakers, such as this one. Some searching shows that they're available from Lowe's and HD (assuming you're in the US), but you should be able to find one in a store near you or online if not.