No matter what type of material you use for your water supply lines, you want leak-free connections. The fastest connection to use is the screw-on nut and washer that’s on the ends of a steel-braided supply line. Simply tighten the nut onto the threaded outlet on the faucet tailpiece and the shut-off valve and you’re set to go.
Another commonly used type of connection is called a compression fitting. It consists of a coupling nut, which secures the fitting to the faucet tailpiece and the shut-off valve, and a brass compression ring, which forms the sealed connection between the supply line and the fitting it’s attached to. Compression fittings are a tighter connection than a screw-on nut and washer fitting. Here’s how to properly install a compression fitting:
Start by sliding the compression nut onto the supply line with the nut threads facing the valve.
Now slide the compression ring onto the supply line.
Place the end of the supply tube into the appropriate valve, making sure that it fits squarely in the valve opening.
If the supply line end doesn’t go in straight, the connection will leak, because the angle of the end of the supply line won’t allow the compression ring to sit or “seat” properly between the supply line and the valve fitting.
Reshape the tube until it fits squarely.
Once the tube is in place, pull the compression ring and nut onto the valve and screw it tight.
Open the shut-off valve to check the connection for leaks.
Keep some rags handy, just in case.