Symptoms
- House still feels humid even with the dehumidifier and AC both running
- Dehumidifier tank fills quickly or barely fills at all
- Humidity levels measured with a hygrometer stay higher than expected
Likely causes
- CommonDehumidifier too small for the spaceAn undersized unit can't keep up with the moisture load in a larger area.
- CommonDirty dehumidifier filter or coilReduced airflow lowers how much moisture the unit can actually remove.
- PossibleDehumidifier placed in a poorly circulated areaA closed-off room or corner limits how much air the unit can actually treat.
- PossibleAC fan set to run constantly, undoing dehumidificationConstant fan operation can re-evaporate moisture off the AC coil back into the house.
- PossibleOngoing moisture source outpacing both systemsA leak, damp crawlspace, or heavy indoor plant watering can overwhelm normal dehumidification capacity.
What to do
- Set the AC's thermostat fan to Auto rather than On to avoid undoing dehumidification between cooling cycles.
- Clean or replace the dehumidifier's filter per its manual.
- Check the dehumidifier's rated capacity (pints per day) against the room or basement size and consider a larger unit if it's undersized.
- Move the dehumidifier to a more central, open area rather than a closed-off corner.
- Use a hygrometer to track actual humidity levels over a few days rather than relying on how the air feels.
- Investigate and address any ongoing moisture source, like a damp crawlspace or a small leak, that could be outpacing both systems.
Tools and parts
- Hygrometer
When to call a pro
Call an HVAC technician about a whole-home dehumidifier system if a portable unit and AC settings still can't keep humidity under control.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.