I’m finishing an old (1930) empty basement and have a random pipe coming out of the floor. ⁠I have no clue what it is or what it went to as it sits alone in the space. ⁠It is metallic (tested with a magnet). ⁠It’s currently capped off and did have threading.⁠ I would say it is 3/4in thick. ⁠⁠⁠I am wondering if I can cut it off and recap or if it’s not able to be cut, if I should build it into a wall?

Thanks in advance!!! enter image description here

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    A metal detector might let you trace the path of the pipe over to whichever wall it goes past. Looking around outside in that area might reveal something. – Wayfaring Stranger Apr 8 '20 at 1:00
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    Nitpick: Testing with a magnet tells you specifically that it's a ferrous metal (or, technically, a ferro- or ferrimagnetic nonmetal, but that would be a very strange thing to make a pipe out of), most likely (non-stainless) steel, not just that it's a metal. Copper, aluminum, lead, or stainless steel pipes wouldn't react to a magnet in the same way, for instance, while still being metal. Although I would hope you don't have lead pipes in your house. – Hearth Apr 8 '20 at 11:40
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    If/when you do find out, please update us. You've piqued my curiosity! – Tom Wright Apr 8 '20 at 14:58
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    @Hearth, unfortunately steel pipes were common in the US for plumbing in the 50s and 60s (maybe longer?) and are still used for non-corrosive applications like gas. – JPhi1618 Apr 8 '20 at 16:02
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    @JPhi1618 I'm not saying that this gives you much information about the pipe. Just that the magnet test isn't enough to distinguish metals from non-metals, since there are common pipe materials that are metallic and do not stick to magnets. (and, technically, there are materials that are not metals and do stick to magnets, but as I said before, those would be very strange choices to make pipes out of.) – Hearth Apr 8 '20 at 17:02

In a basement, galvanized pipe like that could have been a pipe feeding oil from an underground tank to an oil heater that has long ago been removed and replaced with something else. I had one like that and figured it out by looking at where an old chimney had been removed by looking at the sub-floor structures made to accommodate it. I didn't know exactly where the pipe lead until I accidentally found the tank one day in my front yard while digging holes to plant trees. That was an unpleasant surprise, cost me $10k to have the tank removed and the soil cleaned from leaks.

If it was natural gas, it would be black iron pipe, not galvanized. unscrew the cap and smell it, the smell of fuel oil never completely goes away. If water starts to leak out when you loosen it, tighten it up again right away!

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    "If it was natural gas, it would be black iron pipe". Unfortunately, I've seen stranger things, so I personally wouldn't assume that. Especially in such an old house. – stevieb Apr 7 '20 at 22:01
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    Would water coming out mean it’s a capped off water line, I assume? – Aaron Apr 7 '20 at 23:38
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    Water, irrigation or (worse yet) sewer... but sewer pipes are generally not galvanized either. And yes (stevieb) it COULD be a galvanized gas pipe, but that's also a bit large for a gas line too. – JRaef Apr 8 '20 at 6:00
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    @JRaef, sewer pipes are generally somewhat larger than 3/4 inch. – Mark Apr 8 '20 at 19:57
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    If I had to put money down I would guess gas, given time period. It could literally be anything though. – DMoore Apr 8 '20 at 19:57

This could be:

  • water
  • waste
  • gas
  • oil for furnace
  • radon system remnants (unlikely) but the earlier ones used metal pipes
  • other

The picture is pretty clear, this pipe was installed when they poured the foundation. It does something. You are going to have to open that cap and smell and possibly stick something in there so you can see whats further in. Short term if this isn't gas you could get an angle grinder to that and shave it off at floor and fill with concrete.


  1. My money is on gas. It is just we aren't seeing any duct work coming off of this location. If it is a gas line I would just let the gas company close the line - they usually do this for free.
  2. I am not assuming that they poured this floor when house was built in the 1930s. It just doesn't make sense. I am not saying it isn't but the concrete does not look time period and I doubt they would pour a 1" floor. This seems more likely something the home owner did later on to make the space more usable.
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    Re 'other': Prohibition was from 1920 to 1933 and this house built in 1930, there might be a big tank of very nicely aged whiskey – Ack Apr 7 '20 at 22:27
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    Whiskey is the dream, natural gas not so much. If it were from an old oil line, is it ok to cut shorter with an angle grinder? Knowing the floor is only an inch or so thick (very thin floor) would it make since to try to knock the concrete out and see where it goes? – Aaron Apr 7 '20 at 23:38
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    @Ack - worst case scenario it was an air pipe to a hidden room... that is now capped. I am not sure I would try 70 year old whisky. Who am I kidding, I would. – DMoore Apr 8 '20 at 3:42
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    @Aaron if whiskey be sure to invite us all over for a post COVID party in your new room. Re the cap, I would shine a light down it, I expect that it will 90 degree turn somewhere in the range of 4-10" below top of slab. If it does, it probably goes outside. I did would expect the bend to point to the street, uphill, a yard, near a driveway, near the garage, or some combination. It's probably going to a tank. HIGHLY doubt a hidden room. Don't cut until you clear any explosive gases out. I'd probably chip out the concrete so when I put a new cap on it was even with the slab. then fill in around – Ack Apr 8 '20 at 3:59
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    I'm not seeing any patching around the pipe, which would make it part of the original 1930s construction. That rules out the possibility of it being part of a radon system. – Mark Apr 8 '20 at 19:59

I have galvanized natural gas pipe in my 1950 Metro Detroit house. If it's not oil, it could be gas going to the original furnace location. I can see a bright spot in the floor where something stood for a while. It's common to have the furnace in the middle of the house so the heat is distributed evenly. Removing the cap and smelling is probably your best bet. But if it's gas, make sure you use pipe dope when you screw the cap back on or you will have a leak.

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    Hello, and welcome to Home Improvement. Thanks for the answer and keep them coming. And, you should probably take our tour so you'll know the details of contributing here – Ack Apr 8 '20 at 20:00
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    Also as someone noted, TURN OFF THE GAS before uncapping it!! – VWFeature Apr 10 '20 at 2:46

I would check with the city. The previous owner may have taken out a building permit for that work and the local building inspector may have blueprints of it.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know the details of contributing here. – Daniel Griscom Apr 9 '20 at 13:56

If it has a 3/4 inch diameter like you say it's most likely a natural gas line. Don't cut it or gas will fill the basement!! best to turn off the gas and then remove the cap and smell for gas.. You can also have a buddy quickly turn on and off the gas while the cap is off and you can easily confirm that it's a gas line that way.


The way I can see it that looks like a 2: gal pipe with a 2: cap I think it was for a oil drum at one time for a oil furnace. Back in the day they did not use black pipe for a oil burner. Or it could be a waste line of some kind cut the pipe and check and also you can smell what it is.

  • Hello, and welcome to Home Improvement. Thanks for the answer and keep them coming. And, you should probably take our tour so you'll know the details of contributing here – Ack Apr 8 '20 at 21:53

I'm not sure if it is acceptable or legal to put an ohm meter to gas pipes to check for continuity. If it is, you could rig up a set of long leads and test the pipe's association to any other pipes in and around the house. You might be able to find that it is connected to other pipes that you are familiar with. Good luck.

  • It may be just a drain for an air conditioner or humidifier, leading just into grzvel base under concrete. Altough since it is an older home, not likely. – George Stefanopolis Apr 9 '20 at 3:10
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    Using ohmmeter to check continuity is an interesting idea, but aren't gas pipes often grounded to water pipes and other household grounds? In that case you might get a false positive (found continuity between pipes that don't actually connect). – Tim Apr 9 '20 at 19:49
  • I wouldn't want to trust there was continuity across a gas line, anyway. I just was dealing with a gas line yesterday--these days you tape the joints. I wouldn't be shocked if the tape broke the circuit. – Loren Pechtel Apr 10 '20 at 0:06

How long gas has been available in town? Most towns, at least here, have had (natural) gas between 60s and 90s, really bigger towns had "gas factories" between second half of XIX (19th century, meaning 1850-1900) and first half of XX (20th century, meaning 1900-1950) but that gas was used mostly for lighting and cooking, so it's improbable that it would go in the basement (it was expensive and coal was a cheaper option for heat) so my guess is that leads to an oil tank or next to where an oil tank was (usually water was fed from an attic open vase, and flow/return pipes had to be bigger).

  • Could you clarify what you mean by "second half of XIX and XX" ? Is it "19-20" meaning 1950-2050" ? or are you saying some different dates ? – Criggie Apr 10 '20 at 0:33
  • @Criggie Probably centuries. – Richard the Spacecat Apr 10 '20 at 8:47
  • @RichardtheSpacecat so why not specify years rather than this mess? "first half of XX" means 2000 through 2050 ? ie, 30 years in the future from now? Just be accurate, not fancy roman numerals that add confusion. – Criggie Apr 10 '20 at 11:52
  • @Criggie No. See this. Second half of XIX and first half of XX could be a range of about 1850-1950, which seems about right. – Richard the Spacecat Apr 10 '20 at 13:16
  • @Criggie Roman numbers are used in dates for centuries. "my uncle's home is from XVI (century), mine is from the 80" It's clear my uncle's was built hundred lustra ago when mine just ten (lustra ago). – DDS Apr 10 '20 at 14:26

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