[Shop-talk] Soil stack venting issue

[Benjamin Zwissler]

I've had two similar issues.  Both solved and one may be helpful to you.
BTW, my house is all PVC drains, but I'm not sure that matters.

My clothes washer drain shared a pipe with a floor drain and utility tub
(sink).  The floor drain began gurgling when water drained from the other
two.  I tried flushing it but that didn't help.  What did help was using
some bacteria based drain cleaner.  It claims to have helpful bacteria
that, among other things, eat soap scum.  That has worked for many years,
except when I flush a lot of harsh cleaners down the utility sink.  I used
to do some auto part washing in that sink, but don't any longer and I
haven't had to add more bacterial cleaner for a long time.  My thought was
the harsh chemicals were killing the bacteria.

The other example was on my HVAC unit's condensate drain.  It was nothing
but a gravity drain and after many years it began backing up occasionally
and then flooding the whole unit with water.  I could disconnect it and
blow through it and that was enough to clear the clog.  Also using that
pipe was a bathroom and the kitchen sink/dishwasher.  I tried lots of
things (bleach, detergent, bacterial drain cleaners, etc) thinking mold,
moss, grease, etc was blocking it, but in the end I installed an HVAC sump
with a pump that collects a quart or so of water and then pumps it out.
That's worked flawlessly for a few years --- until the pump breaks.

Ben


Ben Zwissler
bjzwissler at gmail.com
812-343-5533
Columbus, IN


On Mon, Dec 7, 2020 at 8:25 AM Jim Franklin <jamesf at groupwbench.org> wrote:

> Maybe some of you have an innovative solution...
>
> My house has a single cast iron soil stack that does both drain and vent.
> When I flush the toilet, it sucks air from the tub drain. The toilet and
> tub enter the stack separately, but at the same height, using an oddly
> specific T with a 4" toilet and a 2" tub inlet about 45 degrees apart. The
> tub does not have its own vent. 2 years ago I had a plumber snake the vent
> from the roof, he found "stuff", and it was fixed. Last week it started
> again.
>
> My kitchen sink T's into the stack at knee height, so it's the highest
> item on the stack. My thought is, because it's a straight T, not a sanitary
> T, stuff from the sink is solidifying inside the T when the flow hits the
> back of the T, and eventually forming a cap of "stuff" just above the T
> entry, sealing off any venting. I can't tell if the sink is also being used
> as the toilet's vent because there are too many walls in the way to hear
> what's happening.
>
> My other thought is that the "stuff" is growing like a mold, and sealing
> it off. Does stuff grow in drains?
>
> Any thoughts on what it might be, and how to prevent it? I rarely put oils
> down the drain, and when I do they are cold and mixed with Dawn to emulsify
> it. There isn't enough canopy for leaves or squirrels to get in the roof
> vent.
>
> thanks,
> jim
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