A refrigerator needs a water supply line when it has an ice maker or it dispenses filtered water. The supply line is usually 1/4-inch copper tubing controlled by a valve that's connected to the 1/2-inch pipe that supplies water to the kitchen sink. The connection between the tubing and the valve and the connection between the valve and the water pipe are often compression fittings, which can develop leaks if you put lateral pressure on them.
The Potential for Damage
When the compression fitting behind a refrigerator begins leaking, you often don't know it until you start to notice water pooling under the appliance. By that time, the water has had ample time to sink into the subfloor, and it can travel along the plywood and affect the floor in other areas of the house. If you have hardwood floors, you may notice cupping in rooms that adjoin the kitchen. Even if the water doesn't cause permanent damage to the subfloor or flooring, it promotes mold growth and may lift vinyl flooring and tiles.
How Compression Fittings Work
Compression fittings offer plumbers an alternative to soldering when joining copper pipes. The fitting consists of a ring that fits on the end of the pipe being connected by the fitting and a compression nut that screws onto the threaded seat on the other side of the fitting. You slide the nut onto the pipe, fit on the ring, insert the pipe into the seat and screw the nut onto the threads. As you tighten the nut, it compresses the ring into the gap between the pipe and seat, and the ring makes the connection watertight.
Problems With Compression Fittings
For the compression ring to form a watertight seal, the pipe must be straight. If the pipe is angled with respect to the fitting, the ring will also be angled, and it may not completely fill the gap between the pipe and the compression seat. Sideways pressure on the pipe can cause a fitting that was watertight when installed to leak. It's easy to put pressure on a the pipe connected to a refrigerator; all you have to do is move the refrigerator to retrieve something that fell behind it or to clean behind it.
Fixing a Leaking Fitting
When you install a compression fitting, the compression ring welds onto the pipe you are joining, and the only way to get it off is to cut it with a hack saw or pipe cutter. Consequently, when a compression fitting leaks, you usually can't reuse it. To stop a leak behind the refrigerator, turn off the water to the house, unscrew and remove the old valve and replace it with a new one. Be sure the pipe in each connection is straight before you tighten the compression nut. Use one wrench to hold the valve steady and another wrench to turn the nut.