Copper Adapters

A copper adapter is the piece that gets you off copper and onto threads. One end is a sweat end, which you solder; the other end has NPT pipe threads. When somebody comes back to the counter with the wrong one, the size was right and one of the ends was wrong. So before you think about size, answer two things about the joint in front of you.

Question one: copper pipe, or a copper fitting?

A regular adapter’s sweat end is a socket: the copper pipe slides into it and you solder it there. A street adapter’s copper end is made to go into a fitting instead, so it plugs straight into the socket of an elbow or tee you already have, with no stub of pipe in between. That saves a joint and some room when you’re working tight against a wall or a joist.

So look at what the adapter has to meet on the copper side. A cut end of pipe takes a regular adapter. An open fitting takes a street adapter.

Question two: male threads or female?

Look at the threaded thing you’re joining to and pick the opposite.

• Joining to a fitting or valve with threads on the inside (female)? You need a male adapter, threads on the outside.
• Joining to a threaded pipe or nipple with threads on the outside (male)? You need a female adapter, threads on the inside.

Put those two answers together and you’ve got the adapter: a male adapter, a female adapter, a male street adapter or a female street adapter.

The sizes

Copper is sold by its nominal size, and a tape on the outside of the pipe won’t read that number. The surest way to get the size right is to bring a cutoff of the pipe, or the fitting you’re replacing, and match it here. Adapters made for copper tubing fit the common wall weights, Type M, L or K, at the same nominal size.

WBC’s male adapters are the same size on both ends:

Male adapter	Sweat end	Male thread
1/2 x 1/2	1/2 inch	1/2 inch
3/4 x 3/4	3/4 inch	3/4 inch
1-1/2 x 1-1/2	1-1/2 inches	1-1/2 inches

WBC’s female adapters below are 3/4-inch copper, with three thread sizes. When an adapter carries two numbers, the first is the copper end and the second is the thread, so a 3/4 x 1/2 solders onto 3/4-inch copper and takes a 1/2-inch threaded pipe.

Female adapter	Sweat end	Female thread
3/4 x 1/2	3/4 inch	1/2 inch
3/4 x 3/4	3/4 inch	3/4 inch
3/4 x 1	3/4 inch	1 inch

That 3/4 x 1/2 and 3/4 x 1 earn their keep when the copper and the threaded line aren’t the same size. One adapter makes the size change and the material change at once, instead of an adapter plus a bushing.

What else goes in the bag

The sweat end needs a clean, fluxed joint to take solder. If you’re doing it yourself, that means a pipe cutter, sand cloth or steel wool for the outside of the pipe, a wire brush for the inside of the fitting, flux, solder for copper pipe and a propane torch.

The Montana winter repair

In a Montana January, a frozen pipe that splits leaves the water off until it’s fixed, and that’s when a wrong guess on an adapter costs the most. Shut the water off, cut out the bad section, and bring the pieces in. Two minutes at the counter matching the copper end and the threads beats a second drive in the cold.

The Pick

For copper pipe into a female-threaded fitting or valve, take the male adapter in 1/2, 3/4 or 1-1/2 inch. For 3/4-inch copper onto a male-threaded pipe, take the female adapter with the thread size you need: 1/2, 3/4 or 1 inch. If the copper side is an open fitting rather than a pipe end, go to the street version of the same adapter.

Frequently Asked Questions

Can I use a copper adapter to connect copper pipe to PEX?

Not by itself. A sweat-to-thread copper adapter gives you a threaded end, so you’d then need a threaded-to-PEX fitting. A direct sweat-to-PEX adapter, which solders to copper on one end and takes PEX on the other, does it in one piece. Either way, match the copper size and the PEX connection system.

What’s the difference between a male and a female copper adapter?

Where the threads are. A male adapter has threads on the outside and screws into a female-threaded fitting or valve. A female adapter has threads on the inside and takes a male-threaded pipe. Both solder to copper on the other end.

What is a street adapter?

An adapter whose copper end goes into a fitting instead of taking pipe. Use one when you’re coming off an elbow, tee or other copper fitting and want to go straight to threads without a short piece of pipe in between.

How do I know what size copper adapter I need?

Match the nominal size of the copper and the size of the threaded connection. On a two-number adapter, the first number is the copper end and the second is the thread. If you’re not sure, bring a cutoff of the pipe or the old fitting and match it at the counter.