Press Fittings
Could someone explain why PEX press fittings don't equate to available pipe sizes.
Pipe sizes 10/15/22/28
press fitting sizes 16/20/25/32
which press fitting should i use for 22mm pipe and what is the 20mm press fitting used for
Advice from 2 local tradespeople
I think that you refer to two different measurement standards for distinct piping systems. The numbers you cited (10, 15, 22, 28mm) are typically nominal sizes (outer diameter sizes ) for copper pipes/tubing, while the press fitting sizes (16, 20, 25, 32mm) correspond to the outer diameter of modern PEX or Multilayer Composite Pipes (MLCP).
The inner diameter of the PEX fitting's must match the pipe's outer diameter to create a secure, watertight seal. To connect a PEX system to a standard 22mm pipe (which is typically copper), you need a specific adaptor fitting. The correct fitting would be a 25mm to 22mm copper adaptor.
The 25mm end of the fitting is designed to be pressed onto a 25mm PEX pipe using a press tool.
The 22mm end (or "outlet") is a copper tail designed to be joined to standard 22mm copper pipework, often using compression or push-fit methods.
A 20mm press fitting is designed for use with PEX pipe that has an outer diameter of 20mm.
You may check the SharkBite push-to-connect (PTC) fittings which are designed to join multiple types of pipe without soldering, glue, or specialized crimping tools.
This design works on PEX, copper, CPVC, PE-RT, and HDPE pipes because these systems are often manufactured to the same Copper Tube Size (CTS) outer diameter specifications. A single fitting can therefore accept any of these pipe types on any of its ends.
https://youtu.be/q0duDB9OMBw?si=Z5NA9Sh3Jp3B5wGv
Perhaps, this may help too.
Nominal vs. Actual Size:
The "name" of the pipe (e.g., 1/2-inch PEX) refers to its nominal inner diameter. However, the critical measurement for any fitting is the outer diameter (OD). For example, a 1/2-inch PEX pipe has an outer diameter of 5/8 inches (0.625").
PEX press fittings (16/20/25/32) are for PEX pipe, not copper.
Copper pipe sizes (10/15/22/28) don’t directly match PEX sizes.
22mm copper usually connects to 25mm PEX using a special adapter.
20mm PEX is its own size, used in Euro-style PEX systems.
You can’t press PEX fittings directly onto copper — use a transition fitting
