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Plumbers installed an outdoor faucet in a requested location by drilling through a block basement wall and installing a hose bib that will not freeze. I asked if a turn-off valve needed to be installed on the inside and they said that wasn't necessary since turning the faucet off outside would shut a valve that is 6" inside the house. I think I understand the basics of these frost-free valves and accepted their suggestion. I also asked if they would seal off the hole somehow, and they said they would apply silicon around the faucet.

They left and I believe they consider the job complete. (An invoice will come in the mail, so I haven't paid for this yet.) I'm surprised to see a large opening into the block, and I wonder if the frost-free faucet will be effective even though there's this gap and the basement is unheated. It is not super cold where I am but does get in the low 20s (F) and one or two months have a daily mean temperature around freezing.

Here's what the install looks like: Outdoor faucet

Interior view of faucet

View through hole faucet was installed in

Does this need a turn-off valve further in the basement? It makes sense to me that it does not. The end of this frost-free faucet is pretty close to where a turn-off valve would go anyway. For context, this is a relatively small house and I don't see any sections of the house's plumbing having shut-off valves, but there are shut-off valves just before every plumbing fixture except this one.

How should this opening in the block be sealed or insulated? Given the importance of the faucet's interior end not freezing and the fact the basement is unheated, I expect this hole needs to be filled in somehow.

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  • It's hard to see from that picture exactly where the valve mechanism is. Unless it's fully inside the basement, you want to keep that hole open so that warm air can reach the valve.
    – SteveSh
    Commented Nov 23, 2022 at 15:58
  • And so far as another inside shutoff goes, they're good to have so you can shut off water to that part of the pluming in case you ever have to work on replace that faucet.
    – SteveSh
    Commented Nov 23, 2022 at 16:00
  • @SteveSh from what I can see, the faucet fixture extends 6" back and ends right around the interior edge of the block wall, where it connects with other fittings and the 90-degree elbow.
    – cr0
    Commented Nov 23, 2022 at 16:28

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Depending on temperature outside and in the basement, a shutoff with drain might be advisable. However, with +20°F rather than -20°F outside, the basement would have to be quite cold indeed to make that a concern here.

While I have seen a properly drained frost-proof sillcock valve in a cold basement freeze and crack due to conducting cold along the pipe, it was indeed -15 to -20°F outside at the time. Usually the issue is failure to remove the hose so it does not drain causing the issue, and that bursts beyond the valve, making for an exciting time when the hose is first used in the spring.

The gap around the pipe is a perfect application for spray foam insulation, or you can stuff it with rockwool or fiberglass if you prefer those. Spend an extra couple of bucks for the firestop foam and worry less about the foam itself being a problem in a fire situation, or needing special treatment on the inside end (equivalent to a layer of drywall) not to be.

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  • Thanks for that input. Makes sense - even as an unheated basement, in this Mid-Atlantic climate I'd be surprised if the interior wall got cold enough to freeze pipes. And if it did, there are many other pipes along that wall! As for temperatures inside that block cavity, what do you think of @SteveSh's point that the hole lets warmer air from the basement flow into the cavity? Maybe helpful for the pipe, but we'd want to fill that cavity if sealing the basement envelope better? (Basement has other drafty windows and a door already so this is probably low priority for insulation sake alone.)
    – cr0
    Commented Nov 23, 2022 at 16:32
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    I'd at least insulate the outer half to two-thirds of it. I doubt that insulating it fully would cause a problem if the valve itself is in the basement and not insulated from the basement. I'd also go looking for other drafty cracks to seal up with the rest of my can of firestop foam...
    – Ecnerwal
    Commented Nov 23, 2022 at 16:34
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    "bursts beyond the valve, making for an exciting time when the hose is first used in the spring." - I can attest to this happening if the hose is left on the faucet, even if it's freeze-resistant. Thankfully it was in an open unfinished part of my basement so only my ego got drenched by the geyser from the split hose. :-)
    – Milwrdfan
    Commented Nov 23, 2022 at 16:45
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    What happens is the water does not drain out if the hose is attahed, so the pipe that's part of the valve in the wall is full of water. Then the outside of that freezes, and the water that remains in it is trapped between the closed valve and the plug of ice on the outside. When enough of it has frozen, the pressure on the rest of it becomes high enough to burst the outer pipe of the frost-free sillcock, and it leaks into the wall cavity or hole. You might not notice it quickly if the hose pressure is not so reduced it's obvious from outside, so it can be a large leak.
    – Ecnerwal
    Commented Nov 23, 2022 at 20:46
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    ...when you open the valve in the spring. In winter, with the valve closed, it's a pretty small leak. Then you go to use the hose and it's quite a large leak, especially if you don't notice it and use the hose for a while.
    – Ecnerwal
    Commented Nov 23, 2022 at 21:47

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