Sub-Zero Water Leak in the Refrigerator: Finding the Source

Read the water before you wipe it up

Before drying anything, take a minute to note exactly where the water is and whether it is liquid or ice, because each source leaves its own pattern. Then dry the whole compartment, lay a folded paper towel in each suspect spot, and look again in a few hours. The towel that gets wet first tells you more than any guess. Water on the kitchen floor in front of the unit is a separate question with its own causes, covered in our page on water under the refrigerator; this guide stays with water you find inside the cabinet.

• A pool under the lowest drawers, or a sheet of ice on the back wall: the defrost drain
• Beads on the gasket, the door liner or the front edge of the shelves: warm air getting past the door
• Drips from the top of the cabinet near the grille, soon after a filter change: the water filter
• Water or an ice slab in the freezer under the ice bin: the ice maker fill or its valve
• A sticky or colored puddle: a spilled container, which is worth ruling out first

A defrost drain that has clogged or frozen

Several times a day the refrigerator warms its cooling coil just enough to shed the frost that builds on it, and that melt water runs down a channel at the back of the compartment into a drain tube, then on to a pan where warmth from the machinery evaporates it. When the drain opening is blocked by crumbs, a scrap of produce, or ice left behind because the last defrost did not fully clear it, the water has nowhere to go and spreads forward across the floor of the cabinet, usually showing up under the bottom drawers. A drain problem comes back within a day or two of mopping, and you may see a glaze of ice creeping across the rear panel. You can melt light ice yourself, but the method depends on the model: Sub-Zero's Classic (CL) and Designer (DET, DEC) guides say to switch the unit off and use a hair dryer on its low setting, kept moving, while the PRO Series guide says to use a handheld steamer and never a hair dryer. Never pick at the ice with a knife or screwdriver, because the coil and tubing behind that panel are easy to puncture, and a sealed-system leak is a far bigger repair than a clogged drain. If the ice is back within a few weeks of melting it, the defrost system itself is suspect rather than the drain.

Condensation from a seal or a door left open

Warm, damp air that gets past the door meets cold surfaces and turns to water, which beads on the liner and runs down to the bottom of the cabinet. Mission Hills sits on the rise above Old Town and the bay, and the marine layer that drifts in on late spring and early summer mornings brings plenty of moisture into a kitchen, so a seal that is only slightly tired can show up as water sooner here than it would farther inland. Run your fingers around the gasket looking for tears, flattened corners or a sticky film, and shut a slip of paper in the door at the top, sides and bottom in turn; wherever it pulls free without any resistance, that section is not sealing. Sub-Zero's cleaning advice for the gasket is simple: turn the unit off, wash with mild detergent and water on a soft cloth, use a paste of baking soda for stubborn marks, and treat mold or mildew with one part bleach to ten parts water, never vinegar or rubbing alcohol. One more clue is worth knowing. On Classic (CL) and Designer (DET, DEC) units the interior lights shut off when a door or drawer has been left ajar, so they stop adding heat; if your lights are out and there is fresh condensation, close everything firmly and give it one hour before deciding anything is broken.

The water filter and the ice maker line

On units with filtered water or an ice maker, a filter that is not fully turned home is the usual cause of drips after a change. For a Classic (CL) model the filter sits behind the grille: lift the grille from its lower edge, twist the old cartridge a quarter turn to the left and draw it out, peel the protective cap from the replacement, seat it and rotate it rightward until it stops, then follow the prompts on the control panel. A forgotten cap or a half-hearted turn is enough to let water escape at the head. After any new filter, Sub-Zero asks owners of non-dispenser Classic and Designer models to throw away the first two full bins of ice, and owners of dispenser models to run water for two minutes, which flushes the line and pushes out trapped air. In the freezer, water spreading under the ice bin or freezing into a slab usually means the fill tube has iced up or the inlet valve is not closing fully, and San Diego's hard tap water leaves mineral scale that can stop a valve from seating. Our ice maker troubleshooting page goes further into fill problems. On Classic and Designer controls, a Snooze/Refresh message means the filter is due; pressing Snooze only puts the reminder off for 24 hours, so replace the cartridge rather than snoozing it for months.

Safe checks you can make today

None of the first steps call for tools or for sliding the refrigerator out of its opening, which you should not try with a built-in: these units are heavy, anchored to the cabinetry and tied into the water line. Work from the front, leave the power on unless a step says otherwise, and jot down what you see so a technician can use it later. Sub-Zero's care guide says to wash the interior with soap, water and baking soda rather than vinegar or alcohol-based cleaners, so use that mix for the cleanup as well.

• Empty and dry the lower drawers and the floor beneath them, then check again after a few hours
• Look for a container that has tipped, or a bag of produce resting against the back wall over the drain
• Check that every door and drawer swings shut on its own and the gasket lies flat all the way around
• Reseat the water filter, confirming the cap is off and the cartridge is turned all the way in
• If water is spreading in the freezer, close the supply valve that feeds the ice maker until it is looked at
• Leave an appliance thermometer on the center shelf overnight so you know whether the cabinet is still cold

When the leak needs a technician

Some leaks are past the towel stage. Call for service if water returns within a day after you have cleared and dried the cabinet, if a sheet of ice keeps rebuilding on the back wall, if the ice maker keeps dripping after the filter has been reseated, or if water is reaching the floor or the cabinetry around the unit. A leak that arrives together with warming is the most urgent combination, because a frozen drain often means the defrost system has quit and the coil is choking on frost; when the freezer still works but the fresh food side is warm and wet, that frosted refrigerator coil is the usual reason. Sub-Zero's own line is that a fresh-food side holding above 48 degrees with the control on 38 will not come back with a coil cleaning and needs service, and our guide to a Sub-Zero refrigerator that is not cooling covers what else to look for. A technician can clear the drain properly, test the defrost heater, sensor and control, replace a torn gasket, and swap a scaled inlet valve. We repair Sub-Zero refrigerators across Mission Hills, Old Town, Middletown, Bankers Hill, Presidio Hills and Morena; call (858) 400-4615 or use the booking button on this page to arrange a visit.