I have a floor drain that is making running water noises. I looked in and saw that there was a stream of water pouring into it from about 6-12 inches down into the drain, from an outlet on the side. There are no toilets flushing, dishwashers running, or any other water source that could cause this.

I do have a sump pump but from what I have read those do not empty into floor drains, they empty outside. It has been raining a little bit, but as of right now it is not and probably hasn't been for a couple hours.

It's not backing up into the basement but I am a new homeowner and do not have any point of reference for what this is and whether I need to be concerned or call a plumber. I have done some googling but haven't found anything there. I also have a general home repair book I looked through but nothing seemed to apply here.

I believe this water has been running for at least a day now, but I haven't been going into the basement lately and don't know exactly how long. As far as I know it's constant.

Where is this water coming from?

  • 1
    Do you have a high efficiency furnace? I have plumbed the discharge into drains before the p trap in the past. I have also seen sumps that do dump into the drains not legal in some areas but legal in others.
    – Ed Beal
    Mar 3, 2018 at 1:36
  • I think so, it's a Lennox Elite, which seems to be a high-efficiency series. I believe it's a few years old.
    – Chris
    Mar 3, 2018 at 1:41
  • 1
    Can you correlate it with the furnace cycling? Mar 3, 2018 at 6:42
  • 1
    I could be your sump, but those generally cycle on and off. Also most places prohibit sump water in the sewer (if you're hooked to a municipal system).
    – Bryce
    Mar 3, 2018 at 6:56
  • 1
    Shut off your main water supply. See if the water stops, or not. Then you'll know if it's environmental, or connected to your water system.
    – Ecnerwal
    Mar 3, 2018 at 17:08

2 Answers 2


You could have a p-trap primer. I found one of these devices connected to the floor drain in my old kitchen/laundry room, when we were remodeling. This device, similar to below, periodically "flushes" the drain and refills it to ensure you have a seal in the drain so that sewer gases do not come back up the p-trap into the house. The device can be hidden in a wall therefore not easy to find, and then a tube of some sort to the drain. Mine was inside the wall, connected to the washing machine cold water line, similar to the second photo. When we remodeled and moved the laundry to the garage, the floor drain was filled in and the p-trap primer was removed from the wall and the line capped.

How often the device worked I am not sure, or how it decided to run, I am not sure.

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I found the culprit, it was my sump pump. A tube at the top led from there to the floor drain, in case of overfilling I guess. They were in different rooms but only a few feet apart.

As for the sump, it was not working because the float was stuck on the wall of the pit. I loosened it and it started working normally. The water drainage stopped after that.

  • 1
    It's the other way around. The floor drain feeds into the sump pump to get rid of the water. There may also be other tie-ins that drain to the sump pit. For example, another floor-type drain, a condensate drain, etc. The gravel under the floor may also drain into the sump pit, especially if a french drain was installed. Consider adding a backup sump pump. As you noted, the floor drain can also be a place for the water to exit if your pump fails.
    – fixer1234
    Mar 4, 2018 at 22:27

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