Dehumidifier not collecting water: how to find out why

First: is there any water to collect?

The most common "broken" dehumidifier we found on service calls was a working one in a room that was already dry. A 50-pint unit earns its rating on the Department of Energy test at 65°F and 60 percent relative humidity. Drop the room to 45 percent, or the temperature into the 50s, and the same compressor pulls a fraction of that, because there is simply less water in each cubic foot of air for the cold coil to condense. A bucket that took a day to fill in July and now takes a week in October may be telling you the basement is fine.

So before anything else, put a hygrometer in the room, away from the unit's exhaust, and read it. If the room is at or below the humidity the unit is set to, the compressor is supposed to be off; most units keep the fan running, which is why it sounds like it is working while nothing happens. If the room reads 60 percent or higher and the bucket is dry, keep going down the list. Our basement humidity guide explains what the room should read and how to measure it properly, and the sizing calculator tells you whether the unit was ever big enough for the space.

The setpoint and the mode

Every portable has a humidity setpoint, and the compressor runs only while the room is above it. Midea's manual for the Cube describes it plainly: in Set mode "the dehumidifier runs until the humidity setpoint has been reached," and its troubleshooting table's first entry under "does not dry the air as it should" is "the humidity control may not be set low enough." Frigidaire's manuals list the same cause as "humidity setting too high."

Two things trip people up. Setpoints get bumped by a child, a cleaner or a power blip that reset the unit to a default of 50 or 55 percent. And the unit's own humidity sensor sits inside the cabinet, in the air it is pulling in, which may read differently from a hygrometer across the room; a unit set to 50 that sees 48 at its intake will idle while the far corner reads 58.

The test is to set the unit to its lowest setpoint or to continuous mode (Midea labels it CO; most brands have an equivalent) and give it an hour. If the compressor starts, the coil gets cold, and water begins to drip, the machine is fine and the setpoint was the problem. Set it to 50 percent for a basement and leave it.

Temperature: too cold to condense

A compressor dehumidifier works by cooling air below its dew point on a coil so water condenses. In a cold room the coil has to run below freezing to get there, and frost forms instead of water. Midea rates the Cube for 41°F to 95°F and tells you to place it where the temperature will not fall below 41°F; Frigidaire's manuals give 41°F to 89°F. In practice the output of every consumer portable falls away steeply below the mid-60s, and a basement or garage in the 50s in spring and fall is the single most common reason a dehumidifier "stopped working" after a summer of filling the bucket.

Frost on the coil behind the filter is not itself a fault. Both manuals say so: Midea's entry reads "this is normal, the dehumidifier has Auto defrost feature," and Frigidaire says frost after a recent start will usually disappear within 60 minutes. Auto defrost works by cycling the compressor off while the fan keeps running until the ice melts. What it means for you is that in a cold room the compressor is off for much of each hour, so the bucket fills slowly or not at all, and if the coil is icing continuously the unit is spending its whole life defrosting.

The fixes are to warm the room (close it up and let the unit's own heat help; a space heater used safely if the space stays below the mid-60s), to move the unit to a warmer spot with the door open to the cold one, or, for a crawl space or an unheated basement that will always be cold, to replace it with a unit rated for cold air. AlorAir's Sentinel HD55 and HDi90 are rated down to 33.8°F with automatic defrost, which is why they are in our crawl space roundup and consumer portables are not.

The bucket, the float and the switch

A portable shuts the compressor off when the bucket is full or out of position, by a float in the bucket that trips a switch in the cabinet. Frigidaire's manual: "when the bucket is full, the unit will shut down and the BUCKET FULL indicator will illuminate." Midea's unit shows P2 for a full bucket and, on pump models, Eb for a bucket that is removed or not seated. Both manuals list "bucket is not in the proper position" as a reason the unit does not start.

So: pull the bucket, empty it, look at the float (a plastic paddle or cup on one side) and make sure it swings freely and sits at the bottom; a float that is stuck up from a sticky residue or a jammed hinge tells the unit the bucket is full when it is empty. Wipe the bucket and the float, check that the bucket's handle is folded down the way the manual shows, and slide it home until it clicks. A unit that shows the full-bucket light with an empty, correctly seated bucket has a failed switch or float, which is a cheap part on some models and a reason to replace on others.

The drain hose: when the water is going somewhere else

If the unit is in continuous drain mode, an empty bucket is the point, and the question is whether the water is actually reaching the drain. Three things go wrong.

The hose runs uphill or has a belly. A gravity drain has to fall the whole way. Frigidaire's instruction is to make sure there are no kinks or elevations in the hose; Midea's is to check the hose connection and that it is properly seated in the outlet. A hose that rises to clear a step, or sags between two supports and fills with a plug of water, stops flowing. On some units the water then backs up into the bucket and trips the full-bucket switch; on others it finds the floor. Shorten the hose, raise the unit on a stand so the outlet is above the drain, and give the hose a continuous slope of about 1/4 in per foot. Our continuous drain setup guide covers the whole install, including a condensate pump for a drain that is uphill.

The drain plug or cap. Midea's "water on floor" entry includes a unit that was meant to use the bucket but had the back drain plug removed, and the reverse happens too: a hose attached with the cap still in place, or the plastic cover over the drain outlet missing after a cleaning so water leaks behind the unit. Check both ends.

The pump, on pump models. A built-in pump has its own filter, reservoir and float. Midea's manual sends you to the pump filter and the pump hose when the pump light blinks; Frigidaire's pump units push water upward to a sink or window with no lift height stated, and a hose longer or higher than the pump can manage stalls it. Clean the pump filter, check the pump hose for kinks and blockages, and test the pump with the bucket in place.

The drawing shows the gravity path the hose has to follow.

The filter and the coil

A dehumidifier moves two to three hundred cubic feet of air a minute across its coil, and the washable filter on the intake catches what is in it: lint, pet hair, drywall dust, the fine grit a basement produces. A clogged filter cuts the airflow, the coil runs colder than designed with less air to warm it, and it ices over. The unit then spends its time in defrost and collects almost nothing. Frigidaire's manuals say to clean the filter every two weeks under normal conditions and light a CLEAN FILTER indicator after 250 hours; Midea's troubleshooting table lists a dirty filter under loud operation, which is the sound of a fan straining against a blocked intake.

Pull the filter (it slides out of the back or the side on most portables), wash it in warm water with a little dish soap, let it dry completely, and put it back. Then look at the coil behind it with a flashlight. Fins packed with dust get a gentle vacuum with a brush attachment, in the direction of the fins; bent fins get a fin comb, not a screwdriver. A coil that is clean, with a clean filter, in a warm room, and still ices solid within an hour points to the next section.

The compressor and the refrigerant: the failures that end it

If the room is humid and warm, the setpoint is low, the bucket is seated, the filter is clean and the bucket is still dry after an hour of running, the problem is in the sealed system, and this is where it stops being a homeowner repair.

The compressor never starts. Set the unit to continuous and listen at the back. Within a few minutes you should hear a click from a relay and then a deeper hum join the fan noise; the back of the cabinet should start blowing slightly warm air. Both Midea's and Frigidaire's units have a three-minute protection delay after any stop before the compressor will restart, so give it that long. No click, no hum, no warm exhaust means a failed relay, start capacitor, control board or compressor. On a portable, a service visit typically costs a large fraction of a new unit.

The compressor runs but the coil never gets cold. Hum and warm exhaust, but the coil behind the filter stays at room temperature and nothing condenses: the refrigerant has leaked out. Midea's units may show an EC code, which the manual identifies as refrigerant leakage detection and tells you to contact service. Portables are built as sealed systems, not serviceable ones; recharging requires a technician with recovery equipment and the leak is rarely found and fixed economically. If the unit is inside its warranty (one year of parts and labor on the Midea Cube and the Frigidaire FHDD5033Y1 per their published terms), start the claim; outside it, this is a replacement.

The sensors. Midea's AS code is a humidity sensor fault and ES is the evaporator temperature sensor; the manual's first step for both is to unplug the unit and plug it back in, and then to call service. A failed humidity sensor can read the room as dry and never start the compressor, which looks exactly like the first problem on this page.

Repair or replace

A portable dehumidifier is a sealed refrigeration system wrapped in plastic, and the economics of repairing one are poor once the problem is inside the sealed system. Fix it yourself when the cause is the setpoint, the bucket, the float, the hose or the filter. Claim the warranty for anything else within the first year, which is the standard term on the units we recommend. Outside the warranty, a compressor, control board or refrigerant failure on a consumer portable is a replacement, and a unit that has given five to eight summers has done its job.

When you replace it, buy for the problem you actually had. If it froze every spring, the room is cold and the answer is a unit rated for cold air or a sealed, warmer space. If the bucket was the recurring failure, buy one with a continuous drain port and run the hose, or a built-in pump if the drain is uphill. If it ran all summer and never got the basement below 60 percent, it was too small, and the sizing calculator will say so. Our basement dehumidifier roundup is built around exactly those three questions; the two below are the ones we point most people to.

When the dehumidifier works and the basement is still damp

If you have run every test above, the unit collects water, and the room still reads above 60 percent a week later, the dehumidifier is not the problem. Either the space is open to a source that outruns it (a vented crawl space, an open window, a dryer vent leaking indoors, a shower without an exhaust fan) or water is coming in through the slab or walls faster than any machine can remove it. The plastic-sheet test in our basement humidity guide tells the two apart in a day. Standing water, efflorescence, a sump that runs constantly or a musty smell that returns within hours of closing the door are water problems, and a bigger dehumidifier only raises the electric bill.

When to call a pro

Call an appliance technician if the unit is under warranty and the manufacturer directs you to one. Call a waterproofing or crawl space contractor, not a dehumidifier, if the basement stays damp with a working unit: that is grading, downspouts, a failed vapor barrier under the house, a cracked foundation or a high water table, and each has a fix that a dehumidifier is not. If a leak is the source, a restoration contractor dries what it wet. The form below reaches vetted local contractors through HelpMeNow.com.