Pipe That Freezes In The Winter

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Jul 17, 2018
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Hi All:

We've been at this house for a 3 years. Every year when it gets 5 above zero or below, our master bath faucet freezes. We've had to let it drip every year and it runs up my water bill. The line running to this is on an outside wall. We live in a one story built on a slab.

We took off the bezel that surrounds the lever to select hot/cold for the bath and you can feel cold air behind there (in the winter months of course).

I've talked to three contractors and they all say the same thing:

This area of the house has been poorly insulated. What needs to happen is removing the siding from the outside, remove the foam board insulation, and insulate the pipes.

The two sinks in this bathroom do not have this problem. Their water supply lines go directly into the floor. We can't really tell but we think the shower supply lines are farther back, farther towards the edge of the slab.

One (retired) contractor suggested pink batting type insulation. The other two said closed cell foam is the way to go. [I'm not going with him, I hear foam is a lot better than batting]

Of the remaining two contractors , one wants to fill it with foam, further box it in with OSB. Insulate the area as much as possible. Reinstall the blue foam that surrounds the house and reinstall siding.

The other contractor said basically the same thing, only he says he'd like to also put a layer of house wrap over it, and maybe even put insulating blocks around the slab edge. He said they make insulation just for this purpose.

I was writing to see if this all seemed legit.

And, has anyone heard of a copper pipe freezing inside a slab in the winter? The coldest it gets here is 15 below.

Would the house wrap make any difference? What about the insulation next to the slab?

I am not a guy who knows about this stuff, and I appreciate anyone's knowledge they can share.

Batt insulation is the least expensive of the 3.

The down side to encasing the faucet in foam, comes when a repair is necessary, and it will.

The slab acts as a thermal mass and will maintain a relatively stable temperature.
The down side to doing this project in warm weather is you can't feel the drafts, so it's harder to guess the path of the cold air. If it's warm enough, you may be able to tell from where the hot air is entering. That would be the same path as the cold air in winter. Once you start to open it up you (and the contractor) will get a better idea of what's needed.
I'm with Snooby on this one: the expanding foam will be a PITA when you need to work on the faucet. Pipe wrap may be enough, but better to overdo it, as you won't want to open it up again in the winter.
Pipe wrap may be enough

No, it won't be enough.
He needs insulation between the outdoors and the pipe, and no insulation between the pipe and the indoors. So that the cold from the outdoors does not reach the pipe, but warmth from the room does reach the pipe.
You only want insulation on the outside of the pipes. No insulation on the inside allows the heat from the house to get to the pipes.
Instead of the expanding foam you may be able to use the sheet of pink or blue closed cell insulation on the outside of the pipe. Only way to know is open up the wall from the outside and then insulate between the studs that the pipe runs between.
The key question is how certain you are about where the freeze is occurring ... or if there could be multiple areas that freeze. It sounds like you've isolated to this one region - that's your working hypothesis.

The foam is fine for a quick attempt- but as other said a total mess if you have to get in there. Murphy will make sure you do have to get in there again. I've used foam a few times - and regretted it every time.

I would open up the patient (wall surgery) and then apply an electric pipe wrap AS A BACKUP while you are in there ... you probably won't need to use it; find a place you can place the plug so that it is accessible but somewhere the wife won't nag you about the chord hanging around ... or just pull it on the inside floor if you want to tick her off (sorry, I have issues in this area). Then apply the insulation outside of the pipe - the bottom line is that you want to leverage the thermal flow from inside the house to keep the pipe from freezing as the other post mentioned.

Now, if you want to geek out a bit and see that the fix is working, put a temperature probe on the pipe in the wall near the concrete slab and another about 5 feet above it - two thermocouples. Have it so you can read the probes after all is put back together. Then you can monitor the temperature for a couple winters. If you find that the pipe temperature is nearing freezing, you can kick in your backup plan - plug in the electric pipe wrap and go take your shower while you think of how you'll redo the insulation the next spring.
The line goes down into the slab right there (we are 98% sure). That’s why I was curious to see if anyone has heard of lines freezing within a slab.

This line runs into my laundry room where it then is tied into the water heater and house water supply. We haven’t had any other faucets/lines freeze. Dishwasher, clothes washer, toilets, sinks, another shower all work fine.

This is our hypothesis, yes. I’m taking the day off the watch what these guys do and ask questions.

Probably won’t go w a pipe warmer in the wall. I know they wouldn’t do it as it’s against code.

The only issue I can see if it’s somehow freezing in the slab.

From what I’ve read it really doesn’t take much of a leak for a draft to freeze a line.

The thermocouple is an idea I have considered. I may buy a couple of these. I’d recommend them if you need something that works w an iPhone. I have one already for a freezer and one in our baby’s crib.

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And I wanted to say thank you for everyone who has replied with their ideas. I really appreciate it.

Contractor should be doing this some time next week.

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