I’ve tried to do some research on this topic but am a little confused and would like to know if I’ve got a problem here that I need to remedy.

I think I want to install a self-draining dehumidifier in my basement. My only reason for doing this is the presence of efflorescence. Not sure if this helps that issue at all or if it will be a non-issue after I seal all the concrete, but I digress. Because I want a self-draining dehumidifier with no sink in the basement, I figured I could see where the AC condensate is being pumped and have the dehumidifier do the same, so I followed that line and found that it just empties the condensate into a hole in the floor. (Picture attached)

Some googling lead me to reading up on slumps but I’m really confused. This hole currently has water in it and I’m not sure how deep it goes. There’s no pump to pump it out of the house if it gets too high

Is this normal? Do I need to do something about it? Any and all advice would be greatly appreciated

image of hole

  • 4
    how do you know that it does not drain into the sewer? ... have you poured in some water to see if level would rise?
    – jsotola
    Apr 2, 2021 at 15:23
  • 1
    Did you mean "sumps"?
    – isherwood
    Apr 2, 2021 at 15:35
  • 2
    You said the hole has water is it standing or flowing?
    – Ed Beal
    Apr 2, 2021 at 15:45
  • 1
    Ok standing water is good , many times with the opening close to the wall they can be clean outs. I saw the mention of water but can’t see it on my phone.
    – Ed Beal
    Apr 2, 2021 at 16:09
  • 1
    @BooleanCheese yes i can see water ... i asked you if you poured in water to see if it drains
    – jsotola
    Apr 2, 2021 at 16:31

3 Answers 3


It's just a typical floor drain, and it's the ideal place to drain your dehumidifier. What you see is the water trap, which prevents sewer gas from escaping. It presumably connects to your sanitary sewer, so be conscientious about what you dump into it.

Here's a modern drain just to illustrate the trap concept:

enter image description here

image source

  • 1
    Isherwood I have never seen that type of clean out on a floor drain in cast. I have in plastic. I was wondering if they left the clean out open, wouldn’t be the first time I found something like that. But hopefully it’s a drain with a trap.
    – Ed Beal
    Apr 2, 2021 at 15:43
  • 1
    I had a similar cast or galvanized one in my previous 1950s home. I can't remember if it had a plug or just an open port. The image is just for general reference with regard to what a trap is.
    – isherwood
    Apr 2, 2021 at 15:48

This is a regular basement floor drain. there is a trap below the slab and that's why you see the water... that's a good sign. You should get a drain cover from your home store similar to the one below. Measure the diameter of the drain and hit the home store or a plumbing supply store for the cover.

enter image description here

  • 1
    There is standing water which is why I was worried. Glad to hear that this is normal, thank you! I think putting in a drain cover would be a good idea to make sure nothing large falls in Apr 2, 2021 at 16:00
  • 5
    @BooleanCheese I'll add, the reason you should probably get a cover ASAP is because vermin (ie. rats) can find their way up through drains like this. Imagine a sewage covered rat running around in your house....
    – Z4-tier
    Apr 3, 2021 at 13:17

My first thought is it’s a floor drain until I notice it is close to the wall. This is a location for a clean out. Can you see standing water? If it is a clean out and not a floor drain it should not be left open. If you see standing water indicating a p trap below the floor it is a standard floor drain and would be fine to continue to use for the dehumidifier drain.

If you see water flowing , no standing water it is a clean out and should be sealed. You can probably still use it by having a trap on the drains into it but it should not be open if there is no trap.

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