My AC condenser unit is on the roof. The wiring and refrigerant lines run through a PVC pipe in the roof. That pipe is sealed with what looks like some sort of foam product:

Exit point on roof

I would like to put a TV antenna on the roof and was thinking that using this existing PVC pipe channel would be the best way out to the roof. I can just follow the existing lines and create another hole through this grey foam.

My primary question is: what sort of product is this and/or what sort of product would be best to use to "reseal" the area where I push the coax through?

Secondarily: Is there any reason I should not run the coax out this way?

Here are some additional photos:

Alternate close up 1 Alternate close up 2 Wider view

  • Is there mains electrical power in there? Nov 28, 2018 at 17:59
  • @Harper Yes, I believe the thicker grey plastic conduit contains the electric lines for the AC condenser.
    – Joe Krill
    Nov 28, 2018 at 18:23

1 Answer 1


before you go poking holes in that check what it looks like from the underside. there may be a solid barrier that you'll need to drill before you can feed the co-ax through.

I see the gray flexible conduit transitioning to a solid white conduit keep clear of the power wires, but being close to the thermostat/control wire should not be a problem.

I'd go with a urethane caulk sealant, this stuff is really sticky, paintable weathwerproof, etc... And should be compatible with what you have there which appears to be some sort of urethane foam. it costs a bit more than silicone caulk though.

squirt some in beside the co-ax and then work the co-ax up and down to spread it out, then add some more in a little cone aroun the top side of the co-ax

Clean up with white spirit (AKA mineral turpentine, Stoddard solvent) so have some handy (and a few rags) because a mess is pretty much guaranteed.

  • So something like Loctite's PL Heavy Duty sealant would be good? They also have a "roof & siding" sealant but it warns that it is not recommended for "Contact with oil-based caulking compounds, butyl caulking compounds and silicone sealants". Can I be fairly certain the existing stuff isn't silicon? Seems the heavy duty would work either way and might actually be more appropriate in this case.
    – Joe Krill
    Nov 28, 2018 at 20:59
  • loctiteproducts.com/p/17/46/pl_seal_hd/overview/… yeah looks ideal. Bostick and Sika have comparable products too.
    – Jasen
    Nov 28, 2018 at 22:39
  • Awesome advice, thank you so much! Thanks for the tip that there may be a solid barrier, too - I did have to drill through wood.
    – Joe Krill
    Nov 29, 2018 at 23:02

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