A refrigerator's ice maker uses all of its water. A standalone undercounter ice maker doesn't. It rinses during its cycles, and on many models the stored ice slowly melts in the bin, so water has to leave the machine every day. Where that water goes is the first thing to settle before you buy one, because the answer decides whether you need a gravity-drain model or a model with a pump.
Gravity or pump: the basic choice
Most undercounter ice makers come in two versions.
- •Gravity drain. Water runs downhill out of the unit into a drain that sits lower than the outlet. No moving parts, but the drain has to be in the right place.
- •Pump drain. A small pump pushes water up and away to a drain that's higher or farther off. More flexible, but it needs power and has limits on how far it can lift.
KitchenAid's guide to drain options says a gravity setup is suitable only when an open floor drain is located immediately below or adjacent to the appliance, and that a pump is needed when one isn't.
The specific numbers
Sub-Zero undercounter ice maker
Sub-Zero's installation guide sets a firm limit for gravity models: the drain connection and all excess tubing, whether behind the unit or in an adjacent cabinet, cannot exceed 7 inches above the bottom of the leveling legs. The guide recommends keeping the tubing as short as possible, says the drain connection accepts 1-inch, 3/4-inch and 5/8-inch connections, and lists 10 feet of corrugated tubing as the drain connection. Pump models connect following local code.
The same guide covers the rest of the hookup: a 15-amp dedicated circuit at 115 volts with a three-prong grounding receptacle, 35 to 80 psi water pressure, and a GFCI that is not recommended indoors (it may interrupt operation) but is required outdoors.
KitchenAid ice makers
KitchenAid's drain page gives the slope for a gravity line as a minimum 1-inch drop per 48 inches of run, or 1/4 inch per 12 inches, with no sagging loops, dips or upward bends. Its pump option lifts water up to 10 feet vertically, and the page warns that pushing past that strains the motor.
KitchenAid's drain hose page adds two rules worth repeating. Use the corrugated hose supplied with the kit, because smooth hose crushes or kinks easily when the unit slides into a tight cutout. And never seal or clamp the discharge end airtight into a household waste line, because a direct connection to a closed pipe can let dirty water siphon back toward the ice bin. It calls for an open standpipe or floor drain with a physical air gap.
Why these rules are strict
- •It's food. The bin holds ice people put in drinks. An open air gap between the drain tube and the house drain keeps sewer water and odors from finding a path back.
- •Gravity only works one way. A 7-inch ceiling is low. If the drain opening is higher, water pools in the unit or backs into the bin.
- •Low spots hold water. A sagging tube traps standing water, which grows slime and smells.
- •Pumps have ratings. Lift height and hose length are finite, and a kink stops a pump just as surely as an uphill run stops gravity.
Where DC installs run into trouble
Undercounter ice makers turn up in a few predictable spots here: basement bars in rowhouses, kitchen islands in renovated row and detached houses, and rooftop or back-deck outdoor kitchens.
- •Kitchen islands. There's rarely a floor drain under an island. Expect a pump model or a pump kit, routed to the sink drain with a proper air gap or air break, depending on what the plumbing code requires.
- •English basements. Basements sometimes have a floor drain, but it may not be close. A gravity line has to fall the whole way at the slope above, which rules out long runs across a room.
- •Outdoor kitchens and roof decks. Sub-Zero requires GFCI protection outdoors. Also think about winter: water left in lines and tubing in an unheated space can freeze. Follow the manufacturer's winterizing instructions if the unit is outdoors.
- •Condos. Adding a drain connection or a new circuit in a condo usually means building approval and a licensed plumber or electrician the building accepts.
Checking a location before you buy
- Decide which version you're considering, gravity or pump. The model number and the guide say which you have.
- For gravity: find the drain and measure the height of its opening from the floor. Compare it with the limit in your guide, such as Sub-Zero's 7 inches above the leveling-leg bottoms.
- Measure the horizontal distance to that drain and confirm the tube can fall at least 1 inch per 48 inches the entire way.
- For a pump: measure how high the water has to rise and how far it has to travel. Compare with the pump's rated lift.
- Confirm the tube will end in an open drain, standpipe or air gap, not sealed into a pipe.
- Check that there's a dedicated circuit within reach of the cord.
What a bad drain looks like
- •Water sits in the bottom of the bin, and the ice fuses into a block.
- •The unit shuts down or slows production because water isn't leaving.
- •Water appears on the floor under the cabinet.
- •A musty or sewer smell near the unit.
Water supply matters as much as drainage for these machines. See appliance water pressure requirements for how to test it.
Licensed work
- •New drains, standpipes or indirect waste connections are plumbing work, and the plumbing code governs how an ice maker drain connects. In DC, plumbing permits listed on the Department of Buildings Instant Permits page are issued only to licensed contractors.
- •A dedicated 15-amp circuit, or an outdoor GFCI-protected outlet, is a job for a licensed electrician.
If your ice maker is already installed and backing up, leaking or making less ice than it should, our ice maker repair technicians check the drain path, pump and fill system together.
Sources
- •Sub-Zero: Undercounter Ice Maker Installation Guide (7-inch gravity limit; drain sizes; 10-foot corrugated tubing; 15-amp circuit; 35 to 80 psi; GFCI indoors and outdoors)
- •KitchenAid: Information on the Different Types of Drain Pumps (gravity vs. pump; slope; 10-foot lift)
- •KitchenAid: Installing the Drain Hose (corrugated hose; no airtight connection; air gap)
- •DC Department of Buildings: Instant Permits (plumbing permits issued to licensed contractors)