Have discovered that our kitchen sink drain appears to be leaking inside the
wall behind the cabinets, and am wondering if I can repair this myself.
Have emptied the space below the sink and cut away a portion of the back
panel to reveal a moldy expanse of sheetrock centering around the passage of
the drain. Can anyone give me an idea as to what might lie behind the
sheetrock, and what I might do about it. We have an appt with a plumber,
but I am sufficiently OCD that leaving this thing alone until he gets here
sometime tomorrow is driving me crazy. Am I a total fool, or is this
something I might reasonably be expeced to be able to fix on my own if I
were to break through the sheetrock? Have to say I was born to fix one
thing or another, and am the one all the family calls on whenever anything
fails to work properly (from computers to kitchen sinks and toilets, as well
as electrical wiring.) The only reason I hesitate is because the wife will
bitch to high heaven about me working in a moldy environment without some
kind of respirator. She knows someone who almost died after raking up some
moldy leaves and breathing the resultant particulates, and lives to tell me
I am doing it wrong or not being carefull enough. I can get a respirator
from the local ACE Hardware or Home Depot, but it looks like the mold
extends along the floor inside the wall to the extent of the kitchen
counter, and I might have to tear all that out to rectify this situation.
It is my understanding that common household bleach in a fairly weak
solution kills mold, but I hesitate to tear half the kitchen apart. Still,
the cost of doing so looks a lot more attractive than the cost of hiring
someone to do it for me (which is how this happened in the first place. We
had the house remodeled about four years ago, and I suspect the contractor
left this half-done just like he left half the other stuff half-done.)
Thanks for any replies. I am looking for input, good, bad or indifferent.
With that much mold, the problem has been going on for a while. So, waiting
one more day until a plumber looks at it won't make any difference in my
Is there a bathroom above the kitchen? Is there a 4-inch stack coming out
of the roof on the outside above the mold is? I had something similar and
it was a damaged/cracked 4-inch sewer line stack that ran up through the
wall behind the kitchen sink and kitchen wall cabinets. It was a very big
job to fix. It involved opening up walls, including the exterior wall on
the back of the house, replacing that section of the stack and fittings with
PVC, and then putting everything back together including the siding on the
back of the house.
P.S. Since you already cut out a portion of the back panel of the cabinet,
it doesn't seem like it would be much of a big deal to also cut out some of
the sheetrock and see what is going on back there. Maybe you'll be able to
see what's leaking and it will give the plumber an idea of what's going on.
Indeed, and that is exactly what I did. Mystery solved. The 2" pipe that
the sink drain eventually connects to, which itself attaches to the verticle
member that becomes the line out was screwed into it's T-joint (forgive my
ignorance, I don't know what it is actually called) without the benefit of
thread compound or teflon tape. And apparently wasn't screwed in too
tightly either. When the water runs, it leaves via the drain and some of it
takes a side trip down to the bottom of the wall between the kitchen and
living room. Leaks at a prodigous rate, in fact. And apparently has been
doing so for the last four or so years, until everything became so saturated
that it could no longer be contained by sheetrock or the ten feet of space
between the line out and the end of the wall behind the counter.
I am tempted to try to fix it, but think I will let the plumber do the job,
just in case it turns out to be more than meets the eye. We have a home
warranty which we have kept up for 27 years, and it is about to pay for
itself again this year. The offending member is up against the outside wall
of the house, and I don't think I want to tackle that. Suspect the plumber
will have to replace the rusted T-joint as well as the loose and rusting
pipe. And that is not something I want on my hands.
Thanks for the reply though. Was beginning to think I must be the total
fool, but just couldn't let it rest another 24 hours.
I'm glad you got to see where the problem is. I can't quite picture the
setup that you are describing, but if the "rusted T-joint as well as the
loose and rusting pipe" means a large 4-inch cast iron pipe, it could be a
very big and expensive job. Or, if the pipes are copper, it could be less
of a big deal. If the pipes are in a wall that is between your kitchen and
living room, they may need to access them through the living room wall
rather than from inside or behind the kitchen cabinets. In any case, if
your home warranty covers most or all of repair work that needs to be done,
that would be great. Let us know how it all turns out.
sorry if I'm not describing the situation very well. The pipes are cast
iron, according to the plumber, and it is a 1.5" pipe (internal diameter)
that is not fitting very well into it's T-section, but that is behind a
rotten stud (2X4) and I really can't see that part. It goes up to a vent
however, and down to the drain, so I am guessing it has to be a T-section at
that particular spot. The home warranty people denied the claim until I can
give the plumber access to the troubled spot, and since it's against the
outside wall of the house that's where he wants "access" to be gained.
Consequently I am having to take down steel siding (on the outside wall of
the kitchen, next to the back door) and cut a hole to expose the troubled
area,. About halfway through at his point. Thanks for your interest. Will
definitely update as progress is made.
Take it easy...
Thanks. That I can picture. I had basically the same situation -- at least
in regard to the vertical cast iron pipe being in the wall behind the sink,
and that being an exterior wall with metal siding and next to a door. The
vertical cast iron pipe in my case was a 4-inch stack that went down to the
drain and up through the roof as a vent. An upstairs bathroom and toilet
also drained into the same 4-inch cast iron stack. Being old and cast iron,
the stack itself had rusted out and was leaking inside the wall. In your
case, the vertical pipe may be 4-inch or maybe 1.5 inches, depending on what
it's function is. If you have a 1.5 inch vertical pipe (drain and vent),
that's easier to work with than the 4-inch pipe. Where the horizontal pipe
goes into the vertical pipe, it is probably leaded into a "Y" fitting that
you can't quite see.
I had two construction-type people who I know doing the work and they did
the whole job. In my case, about 6 or 7 feet of the 4-inch cast iron stack
had to be replaced -- from a point above the sink and behind a wall cabinet
down through the floor with a few fittings to tie into the main 4-inch
stack/drain in the basement. So, it was a complicated job that required
carpentry, construction, and plumbing skills.
One of the two guys I used knew how to carefully un-snap and remove the
metal siding pieces between the door and the edge of the house and mark them
and then was able to re-use the same siding and put it back in place. He
knew the terminology -- something about J-channels or something like that --
and he said there is a special little pry tool that is made for carefully
prying off the old metal siding (although he was able to do without the
tool). I had my doubts about whether taking the old siding off and
re-using it would work, but he was able to do that and the finished product
turned out great. That meant that I didn't have to worry about trying to
match the rest of the siding on the back wall when the siding went back up.
Like you, the best way to access my job was from the outside. Once the wall
was completely opened up from the outside, they were able to cut out the bad
section of 4-inch cast iron stack and replace it with 4-inch PVC. They used
a rubber fitting, known as a Fernco (brand name) to connect the 4-inch PVC
to the 4-inch cast iron. They used an angle grinder to cut off the old cast
Due to all that was involved, it took the two guys about a day and a half to
do the whole job and get everything back together.
One little caution -- be careful when cutting the hole on the back wall to
see the pipes. By that, I mean to be careful that there are no electric
wires in the wall that may get accidentally cut.
Wow. Sounds like your job was a lot more labor-intensive than I expect mine
to be. The vent and drain pipes are the same size as the horizontal one
that is leaking, and they are all galvanized and threaded (you can see and
feel the threads on all the pipes). I suspect that the plumber said the
horizontal member was cast-iron simply because that's what it looked like,
black and fairly rough from all the built up crud it has on it due to the
leaking in the vacinity. You can clean it off however, and it is
galvanized. And threaded on both ends. So anyway, I've cut away an access
port to the T-section, but there are studs on either side of it, and I
suspect I am going to have to take out some of those too. Seriously, I am
tempted to simply knock a small hole in the livingroom wall that will
accomodate the elbow joint on the "near" end of the horizontal member, and
do the replacement of that pipe myself. Patch up the access port, put the
siding back up, and call it good. What irks me is that we are going to have
to replace the kitchen cabinets and redo the "floating" tile floor in there
as well, due to the mold and water leakage over the past four or five years.
Am tempted to take it up with the contractor, who was rated with the BBB,
but I can't really blame him, it was one of his workers who took a shortcut
and thought it wouldn't matter. And that contractor did us a major favor by
stopping everything in the middle of it all and replacing a center support
beam that ran through the attic from one end of the house to the other
because it was half-rotten from having an air conditioning duct sitting on
top of it and sweating on it for twenty or thirty years, without adding
anything to the bill. So I actually feel I owe him big time. <shaking
Glad I was finally able to describe it sufficiently for you to picture it.
Just wish there was an easy way out. But again, thanks for the interest and
encouragement. Suspect it'll be downhill from here.
Take it easy...
Okay, the plumber came out, used the access port I cut in the outside of the
house, and removed the T-joint along wth maybe ten inches (5" either side)
of 1-1/2" galvanized pipe as well as the leaking horizontal member itself.
(I have *GOT* to get a Saws-All.) Turns out the leak was due to the
horizontal member rusting from the inside out, due to it being installed in
such a manner that there was a small pool of water left in the pipe near the
T-section that never drained out. Have to admit I am not totally clear on
how this is possible, but that is indeed what happened. Rusted from the
inside out, right next to the T-section. This pipe was original to the
house, and was fifty-two or fifty-three years old. Not four or five like I
originally thought. The contractor and his head man had nothing to do with
this leak. I just jumped to conclusions. So anyway, T-section and pipe
replaced with PVC. Took about an hour, after which I spent the rest of the
day putting the steel siding back up. Looks good, works fine. Everybody's
happy. We still have to replace the cabinets and possibly flooring, but
believe we can do that ourselves. In the meantime, life goes on.
I thank all of you for your input, and the encouragement to persist and not
try to do it myself. That would have been a big mistake. The home warranty
covered the plumbing costs, and I have a better idea as to how things inside
the wall work. Truthfully, I feel lucky. Believe it could have been a lot
That's an excellent follow-up. It is interesting to see how it all turned
out, what the final answer turned out to be regarding what was causing the
leak, etc. And, yes, a Sawzall is great. I have one, but to be honest, I
don't personally use it a lot. But, I see contractors using them for a ton
of different things. I also have a contractor who uses an angle grinder all
the time for pipe cut-offs etc. Angle grinders seem way more dangerous than
a Sawzall to me, so I don't own one of my own.
I'm glad it all worked out.
I only know what I know, which is steel/iron drains in the walls.
A. A normal kitchen drain has a stub (usually 1 1/2") coming from a T
inside the wall.
That's the hole in the T facing the sink.
B. The top of the T has a vent pipe either going straight up through
the roof or attaching somewhere to another vent pipe that does.
C. The bottom of T has the drain pipe, and takes waste water to the
2. The horizontal pipe leaving the trap under the sink goes into the
stub attached to the T. (A)
All the ones I've seen slip in easily. You normally just dope them up
and slide them in the stub, which is a threaded pipe nipple.
Since the horizontal trap pipe should go into the nipple at least
about an inch for a good seal, it's most often that's a nearly exact
A nut with a rubber or nylon "compression" type washer is then
tightened up. That seals best with a near exact horizontal fit.
Since there's normally very little pressure it won't leak.
That nut should be outside the drywall and in the cabinet under the
Since you can't see it, its a half-assed installation.
Cut out the drywall so you can see it.
The plumber makes you pay for anything he does.
You'll know how it works when you see it.
A possible cause of the dampness/mold is the drain needs to be snaked
and cleaned. Clogging can create enough pressure to overcome a weak
Another possible cause is the water is leaking from elsewhere and
ending up behind the sink.
Hey Vic, sorry for the delay in answering. What you describe is probably
the way it *should* be, but under my sink is a different story. And
half-assed doesn't begin (I don't think) to describe it. The contractor had
his #1 guy do everything in the kitchen when we did the house remodel
number, and that guy got tired of working on our house about halfway
through, I believe. Consequently everything from that point forward left a
lot to be desired. This is just the last thing we have found (and the
worst). I personally think he just didn't like the detail we expected, and
let that show in what he produced. sigh
Thanks for the interest and the description of how it normally works.
Hopefully, by this time next week, we'll have our kitchen back to normal.
Take it easy...
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