Plumbing · L-ACH5N

Double Check Valve Backflow Preventer

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An underground utility vault houses a one-and-a-half-inch Zurn-Wilkins model 950XLT double check valve backflow preventer and a one-and-a-half-inch Hunter IBV brass master valve connected via schedule 80 PVC nipples, elbows, unions, and tees. The assembly rests inside two NDS Pro-Series model 224BCB seventeen-inch by thirty-inch by fifteen-inch height vaults with T-type overlapping bolt-down covers bolted together and installed with the lid in the bottom vault over a four-inch depth of washed drain rock. The vault top sits flush with the finish grade with an eighteen-inch minimum clearance. A separate upstream PVC line features a ball valve from the water meter, while the downstream mainline transitions from schedule 80 PVC to schedule 40 PVC without female adapters. Backflow notes require that the vault does not rest on the pipe, all fittings match the backflow preventer size, all pipe and fittings from the meter assembly through the valve box are schedule 80 PVC, and test cocks receive waterproof plugs per code with sufficient clearance for testing.

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