Hi. After going thru a few crap ones like 1ls and so on. But gathering like 25ml in an hour.
U really need a compressor one..
Meaco have great ones. Have won many best which awards and others. The 20L one is what I got and I use it outside my tent..as unless you're using a sealed tent the Dehumidifier must be in ur grow room. As if u blowing air into tent r using negative seal its the air outside the tent that brings it down to the best affect. For instance if ur room is at 60-65 (tent at 70-75 you'll need bring room down to 40s for big change in tent. Or you can get 2x 12L and do the room/tent.
But, I've found i really don't need to use it tat much. Only when my grow room feel damp i bring it down and keeps the RH 55-65. As to sustain an RH of 50-60 will a boat load lecky. So, with excellent ventilation and air flow in through/around ur plants you'll find you'll only need to use it in the very humid days. Also increases in tent heat will bring it down..