A reduced pressure backflow preventer (12) includes a body (13) defining a passageway (45) for flow of fluid between a supply pipe (14) and a service pipe (16); a check valve (18) positioned in the passageway; a relief valve assembly (20) positioned downstream of the check valve; and a stabilization device for delaying opening of the relief valve assembly. In one embodiment, the stabilization device includes a reservoir (22) coupled to the body and configured to release fluid, thereby to delay operation of the relief valve assembly. In another embodiment, the stabilization device includes a charging device for increasing the effective volume of the region at the service side of the check valve, thereby to delay operation of the relief valve assembly.
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