I have noticed that it is humid in my basement. I ventilate regularly but it is still damp.

I bought a dehumidifier and put it into operation. After less than 24 hours, the 2 liter tank was already 2 times full.

Is this normal or do I have a serious moisture problem in the basement? Is my solution correct? Anything else I can do?

The outside Humidity is according to IBM weather.com around 74- 79%.

  • Is you basement finished? Does it have a concrete floor? Is it entirely below grade? All these things can affect the moisture level in the air.
    – SteveSh
    Aug 17, 2022 at 10:41
  • And what is the outside temperature when weather.com says the outside humidity is 74% - 79%
    – SteveSh
    Aug 17, 2022 at 10:48
  • 1
    You said your basement is damp. How "damp"? You can buy a cheap $15 Bluetooth connected temperature/hydrometer and use that to monitor over time those parameters in your basement.
    – SteveSh
    Aug 17, 2022 at 10:50
  • 2
    That site has a geofence on it. Can't view from outside Switzerland [or maybe outside EU]. There has been [much] recent discussion on portable aircon. Mine can shift 36L [9.5 US Gal] per day with no tank, it blows water vapour outside. I once had a cellar flooded [one-off accident in an otherwise dry cellar], & bought a similar tanked dehumidifier. It became my "life's work" emptying the damn tank several times a day… until eventually it all dried out, after 6 months. Never want to do that again, ever.
    – Tetsujin
    Aug 17, 2022 at 16:22
  • 1
    Sybil - well found, thanks - but yeah, it is what it is. It likely works well, but with a tank that size is going to need constant attention. Perhaps less over time, but it depends where the damp is coming from. Sometimes there's an alternative drain pipe - you could elevate the machine & put a big bucket underneath - you'd lose the auto shut-off feature when full but you might get your visits down to just one a day...
    – Tetsujin
    Aug 17, 2022 at 17:01

4 Answers 4


If the dehumidifier occasionally turns off because it reaches your humidity setting, then it's working and it doesn't matter how much water it is producing.

If it never reaches your set point and runs continuously 24x7, you may need a bigger machine or a second one or you may have an underlying dampness problem that needs fixing.

4 liters a day is not a lot. How much is a lot? Depends on the size of your basement and other things. But 4 isn't.


A 2 liter tank is tiny for a dehumidifier. Every dehumidifier in other than completely casual service I've ever worked with has been set up with a pipe to a drain for the condensate so it can just keep working. Most have a connection for that built into them, or built into the tank. 4 liters in a day in summer is not a particularly large output indicating anything unusual.

Normally basements are somewhat cooler than outside air, so when ventilated with outside air at 74% humidity, it may be 95% or more at basement temperatures.


If you keep going, then either it will collect less over time as it dries out and stabilises.

If it does not, you may need to find a source - one wall damp, a natural spring etc


Humid air is heavier than dray air, so it will be lower to the ground.

Remember the Fog been low to the ground.

No surprise your basement will have higher humidity, specially if the outside humidity is 75-79%

Collecting water from humid air is very good for environment.

It is very clean, has very low content of calc (It is soft), perfect for plants.

  • 3
    This is not correct. Surprisingly, dry air is heavier than humid air. See en.wikipedia.org/wiki/Density_of_air#Humid_air
    – MTA
    Aug 17, 2022 at 13:11
  • Give it a week or two. Everything was saturated before you put it in. It cannot dry it out in a day, it will take several. I would expect in about a week to 10 days the amount of moisture it collects will decline, if not and it runs 24/7 you have some other problems. That is a small basement as you state about 325 Se Ft in the USA.
    – Gil
    Aug 17, 2022 at 20:20

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