Leak after 10 years in house

[terij]

Hi,
After 10 years, we got a watermark in a first floor ceiling with no obvious source. We opened up the ceiling, and found an insulated hot water pipe with the insulation looking ratty and feeling damp. Unfortunately, we took the insulation off without taking a picture.

We did take pictures of the pipe without the insulation. I've attached these below. The weird part is, it seems that the pipe itself is dry. We've watched it for a week or so, and there's no moisture. Any idea of what we should do to investigate this mystery?

Pictures in order of elbow, left side of elbow, right side of elbow, .

Thanks for your ideas,
Teri

 

[Kreemoweet]

That's some pretty nasty corrosion on that pipe. It's common to see some corrosion around joints as a result of
slovenly plumbers not cleaning off their excess flux, but what you show looks pretty extreme. I suggest scrubbing it
off so that the copper is clean. If there's any pitting on the pipe (use a small mirror to check out the back side), the pipe section may
need to be replaced. Be aware that messing with a badly corroded pipe could cause sudden severe
leaking, so you (or a plumber you hire) needs to be prepared to deal with that eventuality.

Alternatively, the water (I assume it is) could be leaking elsewhere, and running down the pipe
to accumulate and drip from what may be a low point.

 

[Sponsor]

 

[terij]

Sorry it has taken me so long to reply. What you are saying about water running to a low point makes sense.

Could water cause that level of corrosion? The insulation around the pipe was soaked and crumbling, so my guess is that it was collecting water for a long time before it actually leaked.

We will clean the pipe like you suggested, and keep the ceiling open to see if we spot any more moisture.

 

[Atomic1]

What climate are you located in? If you're absolutely sure water is not leaking/seeping out of the pipe, consider the possibility of condensation.

 

[terij]

We are in central PA. We thought about condensation, but haven"t figured out where it would most likely start. At the moment, we're still trying to find signs of new water. Any tips on making it obvious? We tried wrapping paper towels without success. Maybe I need to find a material that changes color if it gets wet.

 

[Atomic1]

Interesting. You're in my area then. I have heard of folks in the area getting pinhole leaks in their solder joints in homes decade(s) after the fact.

Are you softening that hot water? Could be possible a thinner type M pipe was used in lieu of L? I have seen copper seeping prior to eventual pinholes.

 

[MKS]

The corrosion maybe from left over flux.
Have you used all the fixtures at and above this level? Could be a drain issue.
Fill up the sinks and tubs and drain them.
Possible toilet overflow. Know this from experience...

 

[terij]

The corrosion maybe from left over flux.
Have you used all the fixtures at and above this level? Could be a drain issue.
Fill up the sinks and tubs and drain them.
Possible toilet overflow. Know this from experience...

We can certainly do that. Is it likely that water from a drain pipe might get caught on a supply pipeÉ

 

[terij]

Interesting. You're in my area then. I have heard of folks in the area getting pinhole leaks in their solder joints in homes decade(s) after the fact.

Are you softening that hot water? Could be possible a thinner type M pipe was used in lieu of L? I have seen copper seeping prior to eventual pinholes.

I had a thought. It's possible that pipe is in a floor joist space that's open to the area behind our gas fireplace, which is a direct vent with the double wall pipe. I wonder if the air temperature back there gets colder due to the pipe.

 

[MKS]

It's possible the leak runs down the pipe in your picture. HJ reminds in another post water follows the laws of physics.
I agree with kreemoweet above.
I would offer up this, if it was a pressure leak in a pipe or joint it would not likely stop. Maybe a shutoff valve was closed for some reason and leaked in this position but not when open. Experienced this.
Jadnashua, reach4 have explained the corrosion here before.
Reach4 or jadnashua have recommended plastic wrap also I believe.
Bathtub overflows can leak also.

 

[Atomic1]

What were the weather conditions when the stain manifested on the ceiling? and how often is the pipe hot?

If this is exposed to a gas appliance duct, are you certain there's no exhaust gasses getting into the joist cavity? Propane exhaust, for example, is laden with moisture. This is why propane garage heaters can cause tools to rust.

 

[Smooky]

If your water is corrosive, it may be corroding the copper pipe from the inside. Eventually pin holes may develop. If the pipe is getting thin and it is slightly porous, there could be a very small leak. If it is a hot water pipe, most of what leaks out may be evaporated before it makes a wet spot. Also if it is a hot water pipe, warm moist air want condensate on a hot water pipe, that usually only happens on a cold water pipe.

 

[terij]

Many, many things to consider here. Thanks to all of you. I will let you know what we find next.

 

[Jadnashua]

For a very small hole, the minerals can close off that hole as the water evaporates. You can get pinholes in pipe for numerous reasons, some of which are: excess acid based flux being left on the pipe, improperly reaming the ends of the pipe straight after cutting them with a pipe cutter (this causes turbulence downstream of a fitting and can literally erode through the metal, but it will take years in most cases), defective pipe, etc.

As suggested, if you try to clean that pipe off, you might remove the mineral plug and it will then leak more readily, but it would then tell you what needs to be repaired (replacement is about the only good option). In some places, the water can be quite aggressive, and it can mess with the pipes. In some places, they almost have to resort to the use of cpvc or pex, as copper just doesn't last. If that were the case where you live, you'd probably have heard about it, though. In the house I grew up in, in many decades, we did have one short section of pipe that developed some pinholes that needed to be replaced. Nowhere else in the house has that occurred...just a bad section of pipe.