We often get phone calls whereby people think that their dehumidifier is faulty because it has stopped collecting water. Even when the display shows a low relative humidity below the set point on the dehumidifier they have trouble believing that this humidity is correct especially when it is next to wet washing or in/close to the bathroom.
The fact is that you can have a whole load of wet washing on a clothes horse and that does not mean that the relative humidity in the room is high enough for a dehumidifier to turn on. Initially the water is sitting in the wet clothes and not in the air so at that point the relative humidity in the room has not been effected. Over time the clothes will dry and the moisture from the clothes will increase the about of moisture in the room air but there is no guarantee that this increase in moisture is enough to bring the relative humidity up high enough to turn the dehumidifier on.
To demonstrate this I took a photo of my own dehumidifier that sits outside our shower room door. We have four children and therefore the shower gets used a lots and this photo was taken in the morning after 6 showers had been taken in quick succession before school and work.
Before the showers the dehumidifier reading was 38%rh, after the 6 showers the relative humidity had only made it 43%rh. With the dehumidifier set to 55%rh it is not going to turn on even though it is sat right next to the wet bathroom.
But the bathroom will dry out reasonable well on its own thanks to the fact that the air humidity is dry anyway.
Before taking these photos I had made sure that the sensor was calibrated so that the readings were correct for this demonstration.
The end result has been that that dehumidifier has sat outside the bathroom door and we have not had to empty the bucket for about ten weeks now, this is because the outside relative humidity has been so dry. But during the winter we were emptying the bucket every day, sometimes twice a day.
This is what can happen with dehumidifiers and it is all normal and not something to be too concerned about.