Pinholes in copper vent pipe

[chel_in_IL]

I'm remodeling my bathroom all the way down to the studs. I was about to hang another piece of sheetrock, when I discovered corrosion on a horizontal piece of vent pipe. I wiped the corrosion away and found holes, which range from 1/5 - 1/3" in diameter.

This is the top level of the house, and no water flows through this pipe. They are vents for a lower level toilet and sink.

What can I do to stop the corrosion, and keep them from getting worse?

As you can see in the picture, it would be difficult to replace this section. (Well, at least for me!)

Michelle in Machesney Park, IL

[master plumber mark]

that is not a good sign to see the top side
of a copper pipe corroded like that....

This usually happens on the bottom side of a pipe that
is immersed in water all the time...

you must have some very caustic sewer gas comming up those pipes and I suggest you do a little more
looking around....


I have seen some pretty rough patches of holes like that
in the past ...people useing everythign from roof tar pitch
to silicone to plug up those holes...

it would be better to cut out that section and replace it with pvc... I would guess that that whole arm is probably paper thin

[chel_in_IL]

Well, I've become pretty skilled with a Sawzall, and it's not a bearing wall, so I could cut out that section of the stud and the pipe and replace the pipe with PVC.

I have septic, have had issues with plugged lines in the yard and a bad lift pump, and have heard that the previous owner had a pump go out every couple of years. So, who knows...

Thanks for your input!

[Gary Swart]

You sure don't want to replace the corroded copper with more copper. It would be very costly at today's copper prices, and certainly for a vent line, PVC would be every bit as effective. I'd just cut out the bad copper and use banded couplings to connect the PVC. I don't know if regular Fernco couplers would be OK on an interior vent line or not. They're not OK on an interior drain line, but the banded would be for sure OK.

[Herk]

Copper DWV is lighter than copper for waterlines. The pipe may have been defective, but that's very rare with copper. I wonder - has anyone that you know of ever had a hair salon in the home? There are some very nasty chemicals involved in that. I recently replaced about 20' of cast iron that may have been about 35 years old because of that - it was completely rotted out for its entire length on the top.

Another odd fact is that it's only the one piece - I have to wonder why. Was it the physics of the thing, or is there more waiting to fail? If you cut it up, you may look at the surrounding pipe to get an idea what's going on.

PVC may be a good way to salvage this, but PVC is likely to have a larger outside diameter than copper. 3" PVC = 3.5" O.D. 3" cu = 3.125" O.D.
2" PVC = 2.375" 2" cu = 2.125".

[chel_in_IL]

Hair salon? Hmm, not that I know of. The neighbors knew the former owners, both who lived here since soon after the house was built.

I did get a step ladder out and inspected the copper piping downstairs, and everything looks fine. The house was built in the early 70's.

I bought the house almost three years ago, and I think anything that could leak, has. We've already replaced the J-pipes for both of the bathroom sinks. They were completely rotted out where it enters the wall.

This bathroom remodel was alot worse that I had originally anticipated (isn't it always?)

Michelle

[Bob NH]

Do you know that there are actually holes in the pipe, or just evidence of corrosion on the outside?

Certainly cutting out and replacing the pipe would be a solution, but there may be an easier way.

It might be possible to clean and flux the area of and around the hole or corrosion and seal the holes with solder, applied with a torch. That would be my first try. I use Oatey No. 95 tinning flux. If the hole is too big to seal with solder, you could solder a small copper patch over each hole.

Before trying to patch it, I would GENTLY poke at it with a nail to see if the material is paper-thin around any hole, or if it is reasonably solid. If it is only about 1/16" diameter you can probably seal it with solder. If larger, you probably need a patch.

If it is not a hole I would clean the spots and tin the area with solder to protect it.

I once had a leak in a 1.5" copper pipe that was caused by a split of a seam that was poorly a manufactured. It was in an area that would have been very difficult to replace and I patched it by soldering a section of pipe over the split.

[chel_in_IL]

Each one of the dark spots on the pipe is a hole. You can compare the size to my pointer finger. The largest is about 1/4".

I did use a wrench to bang around each hole, and it seems pretty solid.

At first, all I saw were little mounds of corrosion. When I scratched those away with the tip of a screwdriver, that's when I discovered the holes.

[markts30]

They make copper X plastic banded couplings to accomodate the difference in OD's... (thicker rubber end goes on the copper)
HD sells them, and if not, your local plumbing supply is sure to have them...
I would replace the pipe section with plastic using the couplings by cutting about 1" from the santees and then just using the bands...

[Marlin336]

I would cut it 1.5" from that 3" x 2" tee wye. Then I would cut that reducing tee wye and that elbow out. That shold give you plenty of room to pull that out without messing with the stud. From there I would re-pipe with PVC exactly as it is now.

If they don't make that reducing tee wye in PVC have all the pipes transfer to PVC with a banded no hub clamp. Put an elbow on the far right side just like it has now. Run that 1.5" line into a 2" x 1.5" tee wye which is installed on the vertical 2". Have a street elbow onto of the tee wye that will take you horizontal and into the tee wye on the 3".

You should be able to get it together either of those ways without cutting the stud out.

[chel_in_IL]

Thanks everyone for your help. Cut the pipe out - found powdered corrosion about 1/2" deep inside the pipe. Removed the left-over ends of the pipes from the brass connectors, and replaced it with PVC and banded couplings.

We would have replaced it with copper, but it is $25/ft. Yikes! I took the old piece of pitted pipe to the scrap yard and got enough for a soda and hamburger from McDonalds.

Michelle in IL

[zhomes]

Is it possible those are screw holes from a drunk drywaller?

[chel_in_IL]

Haha.. no.. they were all around the top of the pipe, and also in the part that was through the stud. But at least that would have been an explanation...

When I went to the hardware store to get parts to fix it, a guy there said he replaced the main vent in someone's house, and it looked like it had been hit with buckshot...

[Verdeboy]

I bet that section of pipe was damaged before it was ever installed. Sort of like when you buy a bruised banana. After a while, it becomes obvious where the banana was bruised.

In this case, it took many years for the bad piece of pipe to make it apparent where the "bruises" were.

[markts30]

I have seen similar corrosion in pipes...
The moisture in the sewer gasses tend to condense and collect on the upper surface of the pipe...
In the event of copper, the sulfates in the sewer gas form weak sulfuric acid and over time eats right through the pipes...
The acids concentrate in the vent and create nice copper swiss cheese.