When you hear about back-flow preventers these days, it's more than likely going to be about their absence. When a backflow preventer isn't where it ought to be, bad things can happen. Things that inspire horror movies like "The Thing that Came from the Sewer" (coming to an unprotected drain near you!). Thefts are also on the rise, not because the product itself is so much in demand; it's the shiny metals that comprise it.
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