My basement has a couple Ethernet and coax cables (thin black and white cables) running from the basement to the attic. The opening also has a gas line, white PVC drain line from the attic HVAC, HVAC power cable (thick black cable), and a power line (yellow cable).

I was thinking about buying this 2 inch PVC conduit to run the Ethernet and coax cables through this opening. I can't fit a 10 foot PVC pipe in my car, so I'm planning on cutting it down to about six feet in the store. The conduit wouldn't run all the way from the basement to the attic, but it would at least clear this opening and separate the Ethernet and coax cables from the other lines. The opening in the attic is at an angle from this opening in the basement (not a straight shot).

Is there a better way to do this? Should I get flexible conduit instead? Or should I just forget about the conduit since I can't run it all the way to the attic.

Problems I'm trying to solve

  1. Separating the Ethernet cables from the power cables to avoid network interference
  2. Make it easier to run new network and coax cable in the future
  3. Prepare this opening for air sealing in the future

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Thank you.

  • 2
    I used 2 inch wide pvc to run my ethernet from the basement to the attic, though i used black plumbing pipe since i didnt need the protection of sch40 where it was being run. Make sure you plug the pipe with fiberglass on both ends so it is not an air pipe Nov 4, 2020 at 2:15
  • 2
    Just diagonal the pipe through your car and let it stick out the window, and stick a red flag on it. Drive carefully. Nov 4, 2020 at 22:43
  • @Harper-ReinstateMonica Second this. Most cars can legally transport a 10' pipe. Nov 5, 2020 at 1:00

4 Answers 4


There's little point in having conduit that goes only part way. On the other hand, a continuous conduit path from attic to unfinished space in the basement is a tremendous asset when low-voltage renovations come up.

Electrical conduit can't have tight bends (elbows) like what's used for plumbing because wires can't be easily or safely pulled through those. Even though the basement-to-attic shot isn't straight, if you can see a path through you can almost certainly get conduit through. If the conduit has to be bent into an arc to get through that's fine.

Cut the conduit as needed for handling and transport then re-assemble it with couplers as you slide the pieces through the structure. Secure top and bottom with straps so that the conduit can't be pulled up or down (think gravity and cable-pulling forces).

The 2" size is very generous for just a few cables but it's still a wise idea. Sooner or later you might want to install a pre-terminated cable such as HDMI or USB; the extra space in the conduit makes that possible. Even 1-1/2" would still be large enough to accommodate almost anything but a DB-25 connector (probably won't be using those ever again though).

  • 1
    However, the relative (lack of) flexibility of 2" conduit .vs. smaller sizes is significant if attempting to "flex it into place" without a straight shot.
    – Ecnerwal
    Nov 3, 2020 at 22:34
  • 1
    Hey now, some of us still have old VGA only monitors...
    – FreeMan
    Nov 4, 2020 at 17:21
  • 1
    @FreeMan You're in luck! The DB-15 connector for VGA will pass through a 1-1/2" SCH40 conduit with just a little room to spare. You won't have to throw out the VGA system merely because the cable couldn't fit. :-) The DB-25 serial cable for the dial-up modem won't go through; it'll have to be adapted to something more modern like DB-9.
    – Greg Hill
    Nov 4, 2020 at 17:31
  • Lemme dig my 14.4 out of storage... ;)
    – FreeMan
    Nov 4, 2020 at 17:46
  • @GregHill In that example, look at using the RJ45 jack to DB25 plug adapter on each end of a standard 4 pair ethernet cable. Length and loss can be an issue though. You can even get VGA plugs that use a round connector on each end of a special extension cable, intended to get signal up to a ceiling mounted video projector.
    – Criggie
    Nov 4, 2020 at 19:46

That hole is a firecode violation. It should be air sealed around the penetrations - as it stands it is a chimney for a fire.

As far as conduit to separate the low voltage wires from the line voltage - are you pulling one end back to get the conduit onto them? a staple and a zip tie to keep the wires to one side of the hole would probably work just as well.

  • Thanks for your reply. My next step after the conduit (or staple and zip tie) is to air seal this opening. The opening is around 8 inches wide. Do you think that rigid foam board insulation, cut to fit, sealed with fire block caulk or foam sealant would work to help prevent this as a chimney for a fire? Thanks again.
    – Ryan
    Nov 3, 2020 at 18:13
  • 3
    @Ryan after you have resolved this, please ask that as a whole new question.
    – FreeMan
    Nov 3, 2020 at 18:25
  • @Ryan - Foam is a poor choice for fire sealing.
    – Hot Licks
    Nov 5, 2020 at 0:07
  • Do you have any links or specific fire code reference with more specific info on this? Are any holes between floors generally a no-no? I bought an older house where the previous owner made some "custom" wiring choices and I'd like to learn more about this so I can get it fixed up, thanks!
    – Tobias J
    Dec 31, 2020 at 16:48
  • The general rule is that you don't want any walls to be able to act as a chimney should a fire break out. Holes that connect wall cavities between floors should be sealed - really you should just seal the holes anyway for pests, air, water. Wall cavities can not be continuous to ceiling cavities. Jan 5, 2021 at 22:56

2 inch PVC is quite large for a few low-voltage cables (coax & cat6 or whatever.)

Check in the electrical aisle of your home improvement store. You'll find GRAY CONDUIT that is specifically meant for electricity and data cabling. It comes in several smaller diameters. Mine stocks 10-foot and I think also 5-foot pieces. They come with one end of the conduit having an enlarged end -- like a PVC fitting manufactured into the piece -- to save you time during assembly, like the green sewer service line pipes.

FYI it's unusual for electricity to cause interference to modern Ethernet. It uses differential signaling and measures the voltage difference between pairs of conductors at the receiving end. The idea is, any induced voltage from interference sources is likely induced in both conductors and doesn't affect the difference in voltage between the two enough to cause problems.

  • 6
    2 inches seems big until you run a dozen or more cat6 cables through it Nov 4, 2020 at 2:11

ENT (electrical nonmetallic tubing) is one option if you have bends that you cannot accommodate with rigid PVC or EMT (electrical metallic tubing - the lightest grade of steel conduit.)

ENT's a corrugated tubing plastic conduit that's quite flexible, so if you are pulling out the current wires so that you can run them or new wires in conduit, you should be able to pull it in while pulling the old wires out. It is commonly nicknamed "smurf tube" (one common color is blue, though orange is more common for data cables, but either is fine, as are other, less common colors.)

However, the pipes already in the chase suggest that it must be possible to assemble rigid assemblies to fit in the chase, and smooth conduit is a lot easier to pull cables in than corrugated ENT, in my opinion.

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