Drain slope between manholes is specified as how many millimeters per meter?

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Multiple Choice

Drain slope between manholes is specified as how many millimeters per meter?

Drain slope is the vertical drop per meter of horizontal run for gravity drainage in conduit between manholes. A slope of 10 mm per meter provides a 1% grade, which gives enough gradient to drain condensate and infiltrated water toward the next manhole without being overly steep. This minimum is commonly specified in OSP design to prevent water pooling inside ducts while keeping installation reasonable. Slopes of 5 mm/m or 2 mm/m are too shallow to reliably drain, and 20 mm/m is steeper than necessary and can add undue stress and cost.

Drain slope is the vertical drop per meter of horizontal run for gravity drainage in conduit between manholes. A slope of 10 mm per meter provides a 1% grade, which gives enough gradient to drain condensate and infiltrated water toward the next manhole without being overly steep. This minimum is commonly specified in OSP design to prevent water pooling inside ducts while keeping installation reasonable. Slopes of 5 mm/m or 2 mm/m are too shallow to reliably drain, and 20 mm/m is steeper than necessary and can add undue stress and cost.

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