insulating around pipes in exterior wall
This is probably a pretty basic question but I want to do this right. I just tore up an exterior wall in a 2nd floor bath to fix a pinhole plumbing leak in the middle of a copper elbow. It was not punctured by anything, it was either a defective piece (12 yrs old) or the leak may be freeze related and just got bigger. The wall section was behind a built in vanity, so the freeze theory comes up because the pipes in that section of the wall are protected from inside air by the front and back of the vanity and the drywall.
The pipes run in about the middle of the thickness of the 2×6 stud. My question is this: should I compress the R-19 batt behind the pipes leaving them exposed to the interior air that infiltrates through the hole that they exit through in the drywall, or should I split the batt so there is no compression and still leave the pipe exposed to the interior wall? Or should I do something else to ward off freezing in this location before putting the sheetrock back?
Thanks!
Replies
If I was doing this I'd be looking at using some 2"or 3" foam between the outside
and the pipe and foam sealing it in place. Then maybe sliding some pipe insulation
on the copper as far as you can
"it was either a defective piece"
Just wonderin if your on a well. Some water has a tendancy to corrode copper,
so this might be an early indication of something else going on.
The ideal thing would be to remove the pipes from the wall. Failing that, DON'T insulate on the WARM side of the pipe -- just on the cold side. Foam insulation is probably a good idea.
Thanks for the replies so far.
In regard to the question of whether I am on a well, the answer is yes. I have done some pretty good checking on the water so far and there is not any of the usual signs of agressive water. pH is 7.8 which is supposed to be ok, hardness isn't high and there is no blue-green staining on any of our fixtures suggestive of dissolving copper. The only thing the water treatment guys said is that I may have high levels of dissolved oxygen....they could test for that but the test isn't very reliable. They suggested I install a thing that leaches phosphate into my home water supply, the phosphate precipitates out on the walls of the pipes coating them with calcium phosphate and "protects" them . Essentially, the thing creates very hard water in my pipes to induce deposits that may protect my pipes. This didn't sound like a good idea.
Any comments would be welcome. This is the first leak we have experienced. Does anyone know if freezing is ever associated with a pinhole leak away from a joint?
Is there any way you could move the pipes?
If you can run them up through the bottom of the vanity, they'd be much easier to access in the future, and wouldn't be likely to freeze.A man is rich in proportion to the things he can afford to let alone. {Henry David Thoreau]
No, freezing will not cause pinhole leaks. Because of the stress distribution caused in the pipe wall by an isostatic internal pressure, such as freezing, freezing always results in splits that run parallel to the direction of the pipe. A pinhole would be caused by something else, such as corrosion, rubbing on some interference, or perhaps poked by a nail.
Thanks Wayne. With no evidence of corrosion anywhere else (or water characteristics that would promote it) and no proximity to any nails or screws (none that were used could reach the middle of the 2x6 stud where the pipe is) I am left with the liklihood that the elbow had a defect in it that resulted in an isolated thin spot and minor corrosion caused the leak.
I have just finished foaming in place some rigid foam insulation with a radiant barrier against the sheathing, to be followed by some compressed fiberglass in the residual space before the drywall goes back.
Thanks for the advice on this.
Yeah, in my limited plumbing experience I've twice gotten bitten by elbows with pinholes in them.
Pinholes in elbows are usually the result of micro hi velocity erosion from failure to properly ream the roller cut end of the upstream pipe or from a blob of excess solder.
Samt
just split the bat
But the ones I've had were in new work. Leaked (weaped) from the start.
Insulate behind pipes with rigid foam. Keep area in front of pipes uninsulated. Box in and seal the sides of the pipe run with more foam to prevent cold air infiltration from anywhere else in the wall cavity. This will give you your best chance in a closed wall.
Another option would be to do all of the foaming as above, but leave part of the foam chase open under the vanity to add some convective warmth from the room.
An escalation would be to put it a hot water recirc setup, which would keep pipe chase warm, and may add convenience to your life besides.