Vent Pipe Leak

romeguy1

Hi All,

I have an older home (built in the 20s) and I am redoing the upstairs
batch. There are 2 exposed vent pipes running up from the downstairs
bath..and on up to the attic. The 2 vent pipes connect in the attic,
make a 90 angle, run horizontal about 4 feet, makes another 90 angle
and runs vertical for a few feet, then horizontal out a dormer. My guess is the various drains in the house (ie, kitchen, laundry, and baths) connect into one of these at some point in the system.

Question #1: In the attic- where the 2 pipes connect there is a joint that is leaking water. Why would there ever be water in this pipe? I thought maybe rain/snow was getting in, but the pipe vents horizontally out the side of a dormer so this is unlikely, or if any water is getting in, I think it would be negligible. The vent pipes (and conncectors) are all cast-iron,
undoubtedly original equipment. Now that the room is pretty much gutted, there is very clear evidence the pipe has been leaking for a long long time. Anyway, if anyone has any ideas as to why this pipe has
a water leak, I would love to hear it.

Question #2: The vent pipes are unsightly and I am thinking about relocating the second one about 4 feet (so it can be near the first one, boxed in, and then hidden). If I cut the pipe below the floor board,
put in a horizontal link, and then make it go vertical again where I want it.
I figure the two pipes connect anyway in the attic why not make them connect on the 2nd floor? I would use PVC pipe to do this, and replace
all the leaky iron stuff in the attic...thus making 2 probs go away.

Any thoughts on this, guys?

Thanks!
Jim

Bonus

Should be some real plumbers along soon, until then...I would guess that the pipe is sweating not leaking, the metal is cold from the outside and the air in the attic is moist. Perhaps it's sweating on the inside and collecting in the horizontals and THEN leaking. Here, you're not allowed horizontals at all in stacks. Can't see a problem with connecting them together lower and changing to PVC, though we use ABS. This would also help if the problem is condensation.
Plumguy, you out there? Anyone? Hello? (ha ha)

romeguy1

Hi Bonus,

Thanks for your advice! I haven't done anything yet with the problem pipe as it's much easier to work on things in the attic when it's DAYLIGHT out, and I haven't been successful this week taking any time off from work to get at it. So until Saturday, I have a bucket in place to catch the drips, which at this point is one about every 30 seconds. ugh.

What's the best way to cut into a cast iron pipe? Sawz-All? Or will a plain old-fashioned hacksaw do the trick?

Bonus

Yeah a sawzall with a metal blade. Hacksaw will work too, but so will you.
A drip every thirty seconds? That's a lot of water! Not sure what's going on there, is the outside of the pipe wet, other than where it is dripping?

romeguy1

Nope, the outside of the pipe doesn't seem wet. Just
the threads at the connection where the 2 pipes join. I do notice that the drip every 30 seconds really only seems to happen after I've used the shower or ran the hot water to shave in the morning. Maybe the warm water going down the drain evaporates somewhat, and the water is the result of the "steam" hitting the cold pipe in the attic?

Eh well, I will find out for sure tomorrow when I get at it. I'm gona cut
the problem pipe completely out and replace with ABS. What's the
best way to connect a cast-iron pipe to a new ABS fitting? Will regular
pvc cement to the trick? I'm wondering how well it bonds to the metal?

Bonus

No, cement won't work, you can get a rubber sleeve with hose clamps on it that you slide over the iron and the ABS and tighten with a screw driver. It does sound like condensation inside the pipe that is leaking out at the joint, bizarre. When I run into iron in houses my general reaction is to remove as much of it as I can reach. Good luck.

romeguy1

Hmmm...now you have me wondering if a rubber connector will be
a permanent thing? Should I put some "goop" on the fitting (maybe a
gasket sealer?) before torquing this all down with the screwdriver?

My thought is that if water is collecting in the current horizontal section, I would expect some water to collect in the new horizontal
that I'm creating as well. How water-tight are these rubber connectors?:confused:

Thanks Boner for all your advice. You're the only shoulder I have to cry on for the moment! :D

Bonus

Hey that's ok: I don't let most people call me Boner.
The sleeve could be used and often is on the 'wet' part of the plumbing so there won't be a problem on the vent. Cut out as much of the iron as you can easily get at, and I suspect the sweating issue wil go away because the ABS doesn't conduct heat like the metal. Is there any way to introduce a slope to the horizontals? Perhaps you can shorten the verts and then slope in between them? BonUS :D

romeguy1

LOL. Sorry BonUS! lmao.

Yes, I intend to do exactly as you suggest and put some angles in those horizonals.

Thanks for all your help!!

Bonus

Let me know how it works out.