I replaced a hose faucet on an exterior wall of my house. In order to do so, we removed the old faucet and had to scrape out some gray goop that was sealing the hole between the wall and the pipe. Now we have the new faucet and pipe and need to know what to put in the gap where the dark gray sealant was. It seemed kind of like caulk.

The wall is made of wood, with a vinyl siding on the outside. I live in a cold climate, the previous pipe had to be replaced because it was leaking, probably due to improper winterizing.

Diagram of problem

3 Answers 3


A common material used by wiring companies such as cable television and telephone installers is a duct seal product. Home Depot sells a multitude of this type of item which is a clay-like substance. It's useful for applications which involve repeated access. It's paintable as well, for those who dislike gray.

duct seal package

duct seal in use

  • 1
    This stuff is great especially on the outside. The only problem I’ve had with it is that it’s hard to get into the cracks between the pipe and the framing.
    – RoboKaren
    Nov 26, 2017 at 2:30

First I would make sure that the pipe is sloping to the out doors so that it will drain. Then a good silicone caulk would work well.

  • +1 Yes silicone will stick well and is durable, they even make "paintable" silicone caulk now. Nov 26, 2017 at 3:29

You could use an outdoor rated caulk on the outside. On the inside you could use spray foam. I’d caution against using spray foam on the outer side because: 1) many foams are not UV resistant and 2) the expansion might warp your siding.

  • 2
    Make sure you use a weather-appropriate caulk. I just did a lot of exterior work in Minnesota and had to use Quad Max as it sticks to most things, cures in low temperatures and can be painted.
    – Jon
    Nov 26, 2017 at 0:01
  • To clarify, are you saying you're apply foam from the inside of the house, and caulk from the outside? Potentially leaving an air gap between (not suggesting that's an issue). Or, would you apply foam from the outside, just deeper into the gap, and then caulk on top of that?
    – SSilk
    Sep 1, 2020 at 19:58
  • @SSilk Don't do that, the caulk will adhere to the PU foam and create 3 points of contact preventing the caulk from stretching if/when expansion or settling occurs. You could foam, put in backer rod, then caulk. Oct 10, 2022 at 18:10

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