| 摘要 |
An improved vented drain insert for insertion into a larger diameter drain pipe, preferably, a roof drain pipe. The insert has a tubular portion which extends into the drain pipe forming an annular restriction in the primary passageway through the drain pipe. A vent tube is provided to provide a secondary passageway from above the inlet to the drain past the annular restriction to the drain pipe below the drain insert. The vent tube is believed to be advantageously vent air and/or equalize pressures below the drain insert under flow conditions in the drain pipe in which air is present in the drain pipe.
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