Mystery leak in the basement
June 25, 2010 9:41 PM   Subscribe

Where did the mystery water come from? There were huge storms in the Twin Cities tonight. We returned home to find a puddle of water surrounding the furnace, which is located in the middle of the basement. There is no evidence of any water near the walls, or any leak from above. Where could this water have come from?

Our home is about 60 years old, but we are new homeowners. There was no evidence of water damage in the basement prior to this storm. The puddle is about 4 feet by 2 feet and is not more than 1/4 inch deep. It looks like where the puddle is is the lowest point of the basement, but there is no evidence of water coming from any other point. The basement is unfinished, so it seems like we would be able to see where it's coming from. So, what could be the cause, and what can be done about it?
posted by violettie3 to Home & Garden (10 answers total) 1 user marked this as a favorite
Was there evidence of splashing (wet surfaces) around the puddle?
posted by silvicolous at 9:45 PM on June 25, 2010

Response by poster: No, there didn't seem to be splashing, although we had two bath mat type rugs down, so it may have been difficult to tell. The rugs were only partly damp.
posted by violettie3 at 9:53 PM on June 25, 2010

Is it a gas furnace with a B-Vent (metal) chimney? When we get horizontal rain the rain cap on the B-Vent of the hot water tank in my shop lets water come down the chimney (on the inside, nothing gets wet but the tank and floor).
posted by Mitheral at 9:56 PM on June 25, 2010

Is there a boiler or hot water heater in the vicinity? I had a Mystery Puddle Incident once, which turned out to be due to the overflow valve on my hot water heater.

If the pressure builds up (due to too-hot water thanks to a broken thermostat in my case), it vents through a valve rather than exploding the tank. Leaving behind a puddle and - if you arrive on the scene early enough - a great deal of steam which, I assure you, is thoroughly baffling if you don't know what's happened.
posted by ErikaB at 9:58 PM on June 25, 2010

Response by poster: It's a gas furnace but has a PVC vent pipe going out the side of the house. The rain was very heavy, so it may be feasible that rain could have come in that pipe and overflowed. However, we don't see more water near the furnace drain hose, which we assume would indicate that was the cause.
posted by violettie3 at 9:59 PM on June 25, 2010

Response by poster: The hot water heater is next to the drain in the floor, and the puddle is more under the furnace than the hot water heater.
posted by violettie3 at 10:01 PM on June 25, 2010

It could have come from the ground- when your basement floods it entails water seeping into the ground, finding a place to pool somewhere along your home's foundation and then being forced through tiny cracks or pinholes in the foundation up into your basement. Usually this seepage is near the exterior walls but it doesn't have to be. When we had seepage owing to my accidentally leaving the garden hose all night, the puddle (or in our case the wettest area of the carpet) was about 4' from the wall but it could have been anywhere.
posted by ethnomethodologist at 10:15 PM on June 25, 2010

Storm sewers are known to flood during storms. Where does the drain lead to? Even if it does not drain into a storm sewer it is possible that wherever it leads was so flooded as to push water up into your basement.
posted by Authorized User at 6:00 AM on June 26, 2010

does your home have a sump pump?

does the puddle include the area with the drain?
posted by lester's sock puppet at 6:19 AM on June 26, 2010

Best answer: I've had water around the furnace from the vent. They make vent caps for this very reason.
posted by Mom at 6:23 AM on June 26, 2010

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