Compression Fittings

Brass compression fittings for soft copper and plastic tube in 1/4", 3/8", 1/2", 5/8" and 7/8" O.D., from BrassCraft: unions, male and female adapters, 90-degree elbows, tees, caps, nuts, ferrules, tube inserts and needle valves. Plus galvanized steel compression couplings from Legend Valve in IPS 1/2" through 2" for repairing steel pipe.

Compression fittings are sized by tube outside diameter, not by nominal pipe size. A 3/8" compression fitting takes tube that measures 3/8" across the outside. This is where most wrong orders start, because copper tube is named by a nominal size that is smaller than its actual O.D.: 1/2" nominal copper measures 5/8" O.D. and takes a 5/8" compression fitting. Measure the tube with calipers rather than trusting the label on the pipe.

Three parts make the joint. A nut, a ferrule (also called a sleeve or olive) and the fitting body. Tightening the nut drives the ferrule onto the tube and it deforms permanently, which is why a ferrule is not reusable once the joint has been made and pulled apart. The seal is metal on metal at the ferrule, so thread sealant belongs on the pipe threads of an adapter and never on the compression seat.

Tube stop or drill through. A standard male adapter has an internal shoulder that stops the tube at the right depth. The drill-through version has no stop, so the tube can pass all the way through the body. That is what you want when you are landing on an existing stub whose length you cannot change, and it is the wrong choice when you need the shoulder to set the depth for you.

Plastic and nylon tube needs an insert. The 63PT tube inserts go inside the tube so the ferrule has something rigid to crush against. Without one, the ferrule collapses the tube and the joint weeps. Not for steel tubing.

Reading a BrassCraft part number. The first group is the fitting type and the numbers after it are sixteenths of an inch of tube O.D. So 60 is a ferrule, 61 a nut, 61CP a cap, 62 a union, 64 a tee, 65 a compression elbow, 66 a female adapter, 68 a male adapter, 69 a compression by MIP elbow and 63PT a tube insert. A 62-10-8X is a union joining 10/16" to 8/16", which is 5/8" to 1/2".

The Legend 303 couplings are a different animal. They are galvanized steel, sized by nominal pipe size rather than tube O.D., and they join two lengths of IPS pipe without threading either end. That makes them a repair fitting for a cut or broken steel line, not a supply-tube fitting.

What is not here: stainless instrumentation fittings, hydraulic compression fittings and metric sizes. Everything in this collection is plumbing brass and steel on inch sizes.

Related: Angle stops · Brass fittings · Ball valves · HDPE and poly pipe