Q: Why don’t the pipes fit North American fittings?
A: Most Chinese-manufactured plumbing systems are built using metric PVC or PPR (polypropylene random) piping. The outer diameters often measure in millimeters — for example, 25 mm, 32 mm, or 110 mm — instead of the North American nominal pipe sizes (¾”, 1 ½”, or 4”). This means your fittings are just slightly too small or too large to fit, even though they look similar.
Q: What type of material am I dealing with?
A: The large 4” and 1 ½” lines are likely metric PVC drain and grey-water pipes. The red and blue ¾” lines are probably PPR or CPVC used for hot and cold water. The brass collars indicate compression or threaded adapters used in Chinese systems — common in European-style push or crimp joints.
Q: Are there adapters for Chinese-to-American sizes?
A: Yes, but they’re specialty parts. You can find metric-to-imperial transition fittings or “metric PVC adapters” through suppliers like McMaster-Carr, Spears, or specialty import plumbing shops. These allow you to glue or thread one end to the Chinese pipe and the other to standard North American fittings. For water lines, look for metric-to-imperial PPR or CPVC adapters.
Q: Can I just sand or heat the pipe to make it fit?
A: No. That’s risky. Altering pipe diameters or using mismatched fittings can cause leaks and pressure failures. Always use proper adapters or couplings designed for conversion between metric and imperial sizes.
Q: What’s the best long-term solution?
A: The best option is to adapt near the home’s entry point. Install metric-to-imperial couplings right where the lines exit the home, then transition to standard North American PVC or PEX for the rest of the plumbing. This way, future repairs and fittings are all standard sizes.
Q: How can I identify the correct adapter sizes?
A: Measure the outside diameter of each pipe carefully in millimeters. Then match it with a metric-to-imperial conversion chart (for example, 25 mm ≈ ¾” nominal). Bring these numbers to a plumbing supplier that stocks international fittings or metric conversion couplings.
For a detailed comparison of pipe sizes and standards, see this Engineering Toolbox PVC size chart.
I’m Chris Mayer, writing for Plumbing 101.