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We have several holes in our house (floor and external wall) that are used for cables (coax and cat5e). The holes are bigger than the cable that goes through them so we'd like to minimize the excess space (to help prevent bugs from getting through).

I can't use caulking or other "permanent" sealers because the cable needs some flexibility and slack.

I've noticed some stoppers/plugs like this:

enter image description here

... but I'm not sure what they're called or where to buy them. I tried searching in my local big box hardware store and didn't see anything in the electrical section. I also searched amazon but must be using the wrong search terms because I can't find them.

Can someone tell me what the name of these stoppers are and where I can find them?

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  • Sometimes called "boots" in the electronics world.
    – Steve
    Apr 14, 2013 at 20:20

5 Answers 5

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They are called "wire grommets" or "electrical bulkhead fittings", and if you search for those (or some combination of those words) you should find what you're after.

I typically seal large exterior holes with expanding foam, and smaller holes with silicone caulk. I've run many cat5 and coax cables through walls, and generally keep the hole just slightly larger than the cable, and it seals up fine. You can leave some slack on both sides (I typically leave a drip loop on the outside and a coil of a few inches on the inside where it's not visible), and that's all the flexibility needed. Silicone caulk has enough give that it is fine for this application.

For a larger cable or a couple cables, I'll go through the exterior wall with a conduit, then seal around the conduit with foam and the outside with silicone (expanding foam breaks down under UV, so it's best to cover the exterior bit with some opaque caulk). At the end of the conduit I'll put a wire grommet in a small box (a 90 degree PVC pull box works great).

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    +1 for grommets. Duct Seal is commonly used to seal wire/cable entrances since it stays soft, can be painted, and won't interact with commonly used plastics or metals.
    – Tester101
    Apr 15, 2013 at 11:26
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    +1 for drip loop. Prevents SOO many issues down the road, including the obvious drips/water problems...And issues related to the old 'Cut twice and it's still too short' problem
    – BrownRedHawk
    Sep 28, 2015 at 16:58
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You can find them at Lowe's and they're called "Feed-Thru Bushings"

enter image description here

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  • sometimes aka mushrooms
    – batsplatsterson
    Nov 20, 2015 at 1:38
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    Odd that this isn't getting any votes, feed through bushing is definitely the search term you want. Other bushings and grommets are more for a hole in sheet metal, these are made for holes drilled in walls. Regarding sealing - I'd use silicone between the bushing and the wall, and duct seal between the cable and the bushing.
    – batsplatsterson
    Nov 20, 2015 at 10:41
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Those are rubber wire bushings and/or grommets. They are commonly used when running LV wires (e.g.- data lines, coax from a sat dish, etc..) in through the exterior of a house.

However, I would be very careful about using them, as they create two surfaces through which water can flow- between the wall and the grommet, and between the grommet and the wire. This is opposed to a single surface when you simply run a wire through a wall.

My suggestion would be to use flexible silicon caulk, regardless if you use a grommet/bushing or not. (my overall suggestion would be to skip the grommet, and just use silicon caulk).

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Caplugs is one company I'm familiar with.

These come from the septic tank industry

enter image description here

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Apparently, you should:

  • use a wall grommet on the inside (like the one you have in the picture)
  • use a Roman nose on the outside with a drip loop to prevent water draining into the house
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