Galvanized Piping or No Vent Causing Clogged Drains/Black Ooze?

D107

Expecting a plumber next week to troubleshoot the black ooze and slow draining problems from our upstairs bathroom sink. I've been told that galvanized piping can cause this. It's possible that behind the sink wall there is a galvanized waste pipe a few feet long. Not sure what other causes there could be. Liquid Plumber used to work, but now no effect. I used to snake the line, but real tired of doing that, and the black ooze would still return all the way up to the sink every few weeks. Even all around the periphery of the sink where it meets the granite top I have to spray water and bleach to keep it under control.

I'd also want to install a mini-vent, even though the fixture is wet-vented in the basement. Plumber says as currently set up, no room for a minivent. Would have to be done on other side of the wall with a service panel. (Note: shower drains fine, so blockage is between sink and where it joins with shower waste line. Shower has its own minivent, hidden by the cellulose insulation.)

First photo below shows the wall years ago before vanity install, second shows vanity installed. You can see it’s PVC at the wall—but don’t know if that means for sure there’s not a galvanized 90 El and vertical line just after that. I guess the sink drain line could be opened and a flashlight could reveal that.



If it is a vertical galvanized line then we can access behind all from a closet. Prior owner says they never opened the bathroom or closet wall. I can't imagine how they would have been able to replace the original galvanized vertical line without opening up one of the walls.

Below is a photo of the 1st floor bathroom ceiling just below the upstairs bathroom which may show everything was done from below. Looks to me like new wood was put above toilet, which would indicate they opened up the floor, in which case line hopefully new copper would have been put in. Pretty sure they did a new floor as I think toilet and shower were moved. Since they went through the trouble of putting in all new copper wastelines, hopefully they installed it in the portion of the sink waste line closer to the fixture--not visible in photo. Note that the visible galvanized nipple has since been replaced with PVC.


If we find that the vertical line in the bathroom just past the sink is PVC, then perhaps best to open the ceiling from below and see what’s going on. That might be a good time to install a service panel door in the ceiling.

If I want to peek through the sink waste line Tee into the vertical line, can I just loosen the fitting at the wall or must I loosen all the fittings, the trap, etc.?

mattmia2

I'd like to hear what others say, but that being essentially an s trap since it isn't vented at the level of the trap, it isn't going to work all that great. Galvanized doesn't clog up on its own so much as it becomes rough as it corrodes and gives the debris and biofilms something to grip on to, but I suspect your issue is more of geometry rather than the piping material. I have also seen either poorly designed or improperly adjusted popup stoppers partially obstruct the drain and restrict the flow and stuff starts forming around the popup and just works it way back to the main riser.

D107

@mattmia2 Hmm..we've lived here for 22 years; prior owners say they never had the problem. We kept their sink for 15 years and gradually started to notice this. We thought the new vanity would solve it.

So if we got in through the back wall, replaced the galvanized--assuming that's what it is––could a minivent be installed on that side at trap level?

Yes, it seems like ours is an attempted P trap but without a vent, so a defacto S trap...

mattmia2

I'll preface this with I'm not a plumber, but my recollection is that a mechanical vent has to be above the drip line of the fixture it is venting. It could be in the wall behind with an access panel at that level to service it and to let air in. I think it could also be on a tee on the pipe heading in to the wall and in a section of pipe that gets it up to the top of the vanity cabinet(although I suppose that is fudging above the drip line a bit).

I have noticed some people turn the faucet on all the way and use the full flow and others just turn it on to a trickle. I think the trickle contributes to clogging, it doesn't run enough water through to flush debris down and in to the main sewer.

Jamie Hall

Sounds just lovely. It's very unlikely that the galvanized pipe is the direct cause, although as @mattmia2 said galvanized, with time, can become rough and contribute to a potential for clogging.

Nor will an S trap directly cause what you are describing. They may pull the trap and let unhappy odours in -- that's why they can't be installed anymore -- but they are no more susceptible to clogging than a P trap.

Your comment that given time you get the black ooze around the rim of the sink under the counter is very concerning, as it suggests that for some reason -- possibly related to the drain configuration, possibly not -- you have a rather severe biofilm/mold problem. Without actually inspecting the whole situation -- and probably taking everything back to the wall apart to allow inspection of the vertical pipe -- I'd not be able to say why, nor what to do about it.

D107

@mattmia2 Ah, interesting. For the last few years we've had a .35gpm faucet filter which probably doesn't help. But we had the same problem when we had a 2gpm faucet.

D107

@Jamie Hall Yes I was also wondering about bio-mold. Will get some testing done. We have that a little in the kitchen sink rim. I have heard that if the plumber uses non-mold resistant putty at the rim it might cause this issue.

About 12 years ago we had the kitchen re-done and they put sheet rock over the plaster nailed into 1x3s. I remember noticing some black blotches on the 1x3s--faded black, greyish stains--and sometimes I've wondered if that could be harmful. I see it a lot in lumberyards.