How to set up a dehumidifier continuous drain

Which setup you need

Walk to where the dehumidifier will sit and look for the nearest place water can go: a floor drain, the sump pit, a utility sink, a laundry standpipe, a window well, a condensate drain already serving the furnace or AC. Then answer one question: is that drain lower than the dehumidifier's drain port, with a path the hose can fall along the whole way?

• Yes: gravity drain. A hose from the unit's drain port, falling continuously to the drain, no pump, nothing to fail. Raise the unit on a stand if you need more fall. This is the right answer whenever it is available.
• No, the drain is higher: a pump. Either a dehumidifier with a built-in pump (the Frigidaire FHDP5033Y1 or Midea's pump Cube in our basement roundup), or an external condensate pump that any dehumidifier can gravity-drain into and that lifts the water to the sink.
• No drain at all within 25 ft: the bucket, a long gravity run across the floor along a wall, or a condensate pump with a long tube to the nearest sink. We have run 40 ft of 3/8 in. tube from a basement corner to a laundry standpipe; it works if the pump is rated for the lift and the tube is secured.

Two numbers to keep in mind. Gravity needs about 1/4 in. of fall per foot of run with no sags; a 20-ft hose needs the port 5 in. higher than the drain, plus a few inches of margin. Condensate pumps are rated by lift: the small ones used under furnaces are typically rated around 15 to 20 ft, and every elbow and every foot of horizontal tube eats into that. Check the pump's rating against your worst-case height before you buy.

Tools and materials

For a gravity drain

• Drain hose. Most portables have a standard 3/4 in. garden-hose thread on the drain port; a short garden hose or a purpose-made 5/8 in. dehumidifier drain hose both work. Midea ships one with both Cubes; Frigidaire's pages list the drain option but not a hose, so buy one. Shorter is better; cut a long hose rather than coiling the extra.
• A stand or shelf for the unit: a sturdy plastic step stool, a milk crate, two concrete blocks and a board. Anything level that lifts the port 6 to 12 in. and lets air reach the intake.
• Hose clamps or zip ties and a few screw-in hooks to hold the hose off the floor along the wall
• A hose washer (the one in the hose end is usually enough)
• Optional: a short piece of 1/2 in. PVC or a hose guide to hold the end of the hose above the floor drain grate

For a condensate pump

• A condensate pump with a reservoir, float switch, check valve and a safety (overflow) switch, rated for at least your lift plus 5 ft. The 1/50 to 1/30 HP units sold for furnaces and air conditioners are the right class.
• 3/8 in. ID clear vinyl tubing in the length you need, plus the barbed fitting the pump comes with
• A short gravity hose from the dehumidifier to the pump's inlet
• Tube clips or zip ties to secure the tube every 2 to 3 ft; a tube-to-standpipe clip or a hole in the sink's drain stub for the end
• A grounded outlet for the pump; most have a 6-ft cord
• Optional but recommended: a drain pan under the unit and a leak sensor in it

For either

• A hygrometer for the far end of the room
• A cup of water for testing

Draining into the sump pit

The sump is often the nearest drain, and it is fine to use with two rules. End the hose above the highest water level the pit reaches in a storm, never below the lid and never under water; a rising pit will push water back up a submerged hose into the dehumidifier. And remember that every pint the dehumidifier makes is a pint the sump pump has to lift out of the house; on a 50-pint unit running hard that is 6 gallons a day, which no pump will notice, but it does mean the dehumidifier should be on a different circuit than the pump. If the pit has a sealed radon lid, drill and grommet a port for the hose rather than leaving the lid cracked.

Draining into a floor drain

Make sure the drain actually works before you trust it with 6 gallons a day: pour a bucket down it and watch it clear. Floor drains with a trap dry out in winter and let sewer gas up; a dehumidifier dripping into one all summer keeps the trap full, which is a side benefit. Keep the hose end above the grate and off to one side so the grate can still be lifted.

Units with a built-in pump

A pump-equipped dehumidifier replaces the external condensate pump with one inside the cabinet and a thin pump hose out the back; the gravity drain port is usually still there for when the drain is downhill. Midea rates the pump in its MAD50PS1QWT Cube for up to 14 ft of lift; Frigidaire says the FHDP5033Y1 pumps to a sink or window but does not publish a lift figure, so keep its run modest. Route the pump hose the same way: up first, then across, secured, air gap at the end. Run the pump once a month in the off-season so the impeller does not seize, and keep the hose short; the small pumps in these units move water slowly and a long hose means the pump runs for minutes at a time.

Troubleshooting a continuous drain that stopped

• Bucket-full light on with the hose connected. Water is backing up: a sag, a kink, a hose end under water, or a drain port cap left in place inside the unit. Walk the hose from the unit to the drain.
• Water on the floor under the unit. A hose washer missing or the hose cross-threaded; or the internal drain pan overflowing because the port is blocked with slime. Pull the hose and flush the port.
• Pump runs but nothing reaches the sink. Lift beyond the rating, a kinked tube, a check valve stuck shut, or a split in the tube near the pump. Test with the reservoir full and watch the tube.
• Pump cycles every few seconds. Check valve failed; the tube drains back and refills the reservoir. Replace the fitting.
• Slime and smell. Normal after a season. Vinegar flush, replace the vinyl tube every couple of years; it yellows and hardens.
• Nothing drains in winter. The room is below about 65°F and the unit is making little water, or below 41°F and not running at all. That is the unit, not the drain.

When to call a pro

A drain hose is not a trade. But if the only drain in the basement is a floor drain that does not clear, a sump that overflows, or a standpipe that backs up, the dehumidifier is the least of it: get a plumber to fix the drain. If the basement needs a dehumidifier year-round and there is no drain within 25 ft, a plumber can add a condensate line to the sewer with a proper trap in an hour or two, which is a better long-term answer than a 40-ft tube. And if the basement is wet rather than damp, no drain setup fixes that; our 72-hour dry-out guide and the crawl space roundup cover the bigger machines, and the form below reaches a local contractor.