Name that puddle
August 22, 2021 5:13 PM Subscribe
We have discovered a large puddle in our garage. The consistency is oily, but it doesn't match any fluids we could identify in our car, and the location of the puddle does not suggest that it came from the car (it's nearer to the wall shared with the house). How do we figure out what this is and how much to worry?
We just had ductless A/C installed, and the line with the coolant comes through the garage attic, with the exit from the house roughly above the puddle, but the HVAC tech they sent out couldn't identify a leak anywhere in the coolant line. He said it's not impossible, but it would have required some really bad luck to pierce the coolant line by mistake, and we should look elsewhere. The air conditioning is still working, and if there'd been a substantial coolant leak, it seems like it shouldn't be.
The puddle is also directly below one of our chimneys. Not sure there should be anything wet in there.
My husband also thought he saw a bubble in the puddle, which invites the worrying speculation that it comes from beneath. Our house is almost 100 years old and who the heck knows what lies below? Does any place keep records of this type of thing, e.g. "this house had an oil tank underground before everyone realized that was a super bad idea"?
We just had ductless A/C installed, and the line with the coolant comes through the garage attic, with the exit from the house roughly above the puddle, but the HVAC tech they sent out couldn't identify a leak anywhere in the coolant line. He said it's not impossible, but it would have required some really bad luck to pierce the coolant line by mistake, and we should look elsewhere. The air conditioning is still working, and if there'd been a substantial coolant leak, it seems like it shouldn't be.
The puddle is also directly below one of our chimneys. Not sure there should be anything wet in there.
My husband also thought he saw a bubble in the puddle, which invites the worrying speculation that it comes from beneath. Our house is almost 100 years old and who the heck knows what lies below? Does any place keep records of this type of thing, e.g. "this house had an oil tank underground before everyone realized that was a super bad idea"?
Best answer: Do you have a bag of magnesium salt ice melt, and have you had humidity swings?
posted by bfranklin at 5:41 PM on August 22, 2021 [2 favorites]
posted by bfranklin at 5:41 PM on August 22, 2021 [2 favorites]
You don't mention any garage ceiling evidence, but you do consider the possibility that the recent HVAC work could be implicated. What else can you say about the "garage attic?" Is that open space or is it enclosed?
posted by Glomar response at 5:45 PM on August 22, 2021
posted by Glomar response at 5:45 PM on August 22, 2021
I'd try to determine if it is a one time spill from above or if it ongoing from below. Even a small amount of oil spilled from above will spread over time on concrete.
An oil absorbent (available at auto stores) will absorb excess liquid. Allow the absorbent to remain in place for a few hours, then sweep it up. Then place a scrap cardboard box over the area to see if there is any liquid dripping down or reappearing from below.
posted by tronec at 10:20 PM on August 22, 2021 [2 favorites]
An oil absorbent (available at auto stores) will absorb excess liquid. Allow the absorbent to remain in place for a few hours, then sweep it up. Then place a scrap cardboard box over the area to see if there is any liquid dripping down or reappearing from below.
posted by tronec at 10:20 PM on August 22, 2021 [2 favorites]
Response by poster: Thanks, all. Mr. eirias tells me the oily substance is odorless and colorless. There is no ceiling staining. It's pretty close to the wall, so we had the thought that it might be dripping inside the wall and seeping out. But if so, it's not seeping on the other side, in the basement, that we can see.
The garage attic is an enclosed but not insulated room over the garage -- storage, that kind of thing.
Not sure about magnesium salt, bfranklin -- can you say more about why you asked? We do keep ice melt on hand in the winter although I don't think there's been a bag in that particular spot anytime recently. It's certainly been humid here.
Thanks, tronec, those were good suggestions. We've done those things and now we wait.
posted by eirias at 3:32 AM on August 23, 2021
The garage attic is an enclosed but not insulated room over the garage -- storage, that kind of thing.
Not sure about magnesium salt, bfranklin -- can you say more about why you asked? We do keep ice melt on hand in the winter although I don't think there's been a bag in that particular spot anytime recently. It's certainly been humid here.
Thanks, tronec, those were good suggestions. We've done those things and now we wait.
posted by eirias at 3:32 AM on August 23, 2021
If you have a car with an air conditioner, this may just be condensate from the AC unit in the car being expelled when you park. How large is large? This water sometimes has a slightly oily sheen to it, but is ultimately just water, and would flow to a low spot in the garage floor.
Also, has it rained there recently? If so, water could be infilrating the chimney, or creeping down the air conditioner lines if they werent' sealed properlay where they enter the house wall.
posted by cosmicbandito at 7:08 AM on August 23, 2021
Also, has it rained there recently? If so, water could be infilrating the chimney, or creeping down the air conditioner lines if they werent' sealed properlay where they enter the house wall.
posted by cosmicbandito at 7:08 AM on August 23, 2021
Seconding AC condensate, or otherwise dripping from a car.
Our mystery puddle is the refrigerator; we have an old fridge in the garage and I think it spills a little water out the back when it auto-defrosts itself. This is a pretty random occcurence, so we don't see a puddle near the fridge, but halfway to the door. which was freaky the first two times, but that's my best guess.
posted by adekllny at 7:57 AM on August 23, 2021
Our mystery puddle is the refrigerator; we have an old fridge in the garage and I think it spills a little water out the back when it auto-defrosts itself. This is a pretty random occcurence, so we don't see a puddle near the fridge, but halfway to the door. which was freaky the first two times, but that's my best guess.
posted by adekllny at 7:57 AM on August 23, 2021
Response by poster: The puddle came back, and appeared to do so underneath the cardboard. Mostly. One obvious Jackson Pollack style splatter on the top layer. No evidence at all of ceiling impingement. WTAF?
I remembered bfranklin's comment and said to Mr. eirias, well one person on MeFi asked if we had road salt. Mr. eirias got a gleam in his eyes -- adjacent to where the puddle reappeared today was the salt tub. We flipped it -- a hole in the bottom! He felt the now-congealed mass of salt -- the same oily feel as the puddle!
I guess this is probably it. Why is this it?? There was *a lot* of this nonsense. What do we do to clean it up? More Oil-Dri?
posted by eirias at 3:26 PM on August 23, 2021 [1 favorite]
I remembered bfranklin's comment and said to Mr. eirias, well one person on MeFi asked if we had road salt. Mr. eirias got a gleam in his eyes -- adjacent to where the puddle reappeared today was the salt tub. We flipped it -- a hole in the bottom! He felt the now-congealed mass of salt -- the same oily feel as the puddle!
I guess this is probably it. Why is this it?? There was *a lot* of this nonsense. What do we do to clean it up? More Oil-Dri?
posted by eirias at 3:26 PM on August 23, 2021 [1 favorite]
Salt is hygroscopic. It will attract moisture from the air and turn into a liquid solution. The more humid the air, the faster the process.
Concrete is porous.
Many liquids will spread out over a larger area over time when put on top of concrete.
If the salt solution remains it will eventually dry out leaving a salt stain on the concrete. Google "remove salt stains from concrete" for many options. Most seem to utilize a vinegar and detergent mixture. I've had good success using a wet/dry shop vac to suck up many things including cleaning liquids.
There are more expensive options for cleaners specifically designed for salt.
Glad you were able to locate the source and that it was not a long-forgotten underground fuel tank!
posted by tronec at 5:07 PM on August 23, 2021 [2 favorites]
Concrete is porous.
Many liquids will spread out over a larger area over time when put on top of concrete.
If the salt solution remains it will eventually dry out leaving a salt stain on the concrete. Google "remove salt stains from concrete" for many options. Most seem to utilize a vinegar and detergent mixture. I've had good success using a wet/dry shop vac to suck up many things including cleaning liquids.
There are more expensive options for cleaners specifically designed for salt.
Glad you were able to locate the source and that it was not a long-forgotten underground fuel tank!
posted by tronec at 5:07 PM on August 23, 2021 [2 favorites]
I'm happy you figured it out. To answer your question, I have also played this same game to figure out an oily, colorless, odorless garage puddle. I was fortunate in that my bag of ice melt was one of only a couple things touching the puddle. I felt the oily weeping when I moved the bag.
posted by bfranklin at 6:24 PM on August 23, 2021 [1 favorite]
posted by bfranklin at 6:24 PM on August 23, 2021 [1 favorite]
This thread is closed to new comments.
posted by jon1270 at 5:17 PM on August 22, 2021 [1 favorite]