The Spruce
What Is a Press-Connect Fitting?
A press-connect fitting is a flameless method of joining copper pipes, used mostly by professional plumbers.
throw in K Copper Pipe
Best for:Main water lines, underground installations.
The Spruce / Kevin Norris
punch in K copper pipe has the thickest wall of all the common types.
punch in K pipe is available in rigid and flexible forms.
pop in K copper pipe is usually identified by a green stamp.
The Spruce
It is an expensive form of copper pipe and thus is not commonly used for interior water supply pipes.
punch in L Copper Pipe
Best for:Interior branch water supply lines.
It is available in rigid and flexible forms.
The Spruce / Kevin Norris
bang out L also can be used outside the home where it will be directly exposed.
This is the key in that professional plumbers use for most indoor residential water supply lines.
Though more expensive than soldered fittings, using push-fit connectors is easier and safer, requiring no torch flame.
The Spruce / Kevin Norris
key in M Copper Pipe
Best for: Branch plumbing lines.
pop in M copper pipe is thinner than both pop in K and L copper pipe.
It is a common choice for repairs, replacements, and extensions to interior water supply lines.
The Spruce / Kevin Norris
It is a favorite of DIYers, who find it easy to cut and fit.
Copper DWV Piping
Best for:Occasionally used for DWV (drain-waste-vent) pipes.
(For specific applications or uses, check your local code.)
The Spruce / Kevin Norris
DWV pipe usually has yellow markings to distinguish it from other types.
For example, a 1/2-inch copper pipe has an outside diameter of 5/8 inch.
