Plastic waste pipes are measured by their outside diameter (OD), not their inside diameter (ID).
This is a critical distinction to ensure proper fitting and connection of pipes and fittings. Here's a breakdown:
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Why Outside Diameter? The outside diameter is the standardized measurement because plastic pipes need to fit snugly into the sockets of fittings (couplings, elbows, tees, etc.). Measuring the outside diameter ensures compatibility and a secure connection.
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Inside Diameter Variability: The inside diameter can vary depending on the wall thickness of the pipe. Different pressure ratings or manufacturing processes can affect the inside diameter, making it an unreliable measurement for ensuring proper fit with fittings.
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Pressure Rating Doesn't Matter for Measurement: The pressure rating of the pipe (e.g., Schedule 40, Schedule 80) doesn't determine how you measure the pipe. While pressure rating affects wall thickness and pipe strength, the outside diameter is still the standard for sizing.
In Summary: Always measure the outside diameter of plastic waste pipes to determine their size. This ensures proper compatibility with fittings, regardless of the pipe's pressure rating or wall thickness.
