Plumbers: what is this mystery piping?

Question

I just demo'ed an old bathroom in the basement of my 1920 house so I can upgrade it.  It was a slapped together job by the previous homeowner so most of it was pretty funky, but what I found when I tore off the old laminate wallboard behind the sink and toilet really baffled me.  I knew there was a 2" PVC vent pipe there because it exited to the outside through a basement window above the toilet (they had removed the glass and filled it in with plywood then buried the window behind the paneling).  But when I exposed the wall framing I saw the 2" vent only came off the drain under the floor beside the toilet.  The sink drain was tapped off a separate 2" pipe coming out of the floor (so far so good) but this pipe continued above the sink tap, went up in the wall about 3' then did a 90 to the right, went another foot, 90'ed back down another foot, 90'ed left and reconnected with the same pipe just above the sink tap -- in other words there is a square loop of 2" pipe that reconnects to itself above the drain tap.  No connection at all between it and the toilet vent stack and no vent to the outside.  What the heck is that?  Why would they have not just 90'ed the riser from the drain tap to the left and teed it to the toilet vent right beside it?  Never seen anything like this.

Needless to say I am going to redo all the vents, but I just wondered what a an unvented closed loop like that stacked above a drain tap was supposed to accomplish.  Or is it just another "clueless handyman" oddity?

Whoever last plumbed this basement was crazy anyway.  There are no less than 4 pairs of laundry hookup valves (4 hot and 4 cold) lined up along one wall side by side.  This is a 2 bedroom single family house so I doubt they would have needed 4 sets of washing machines.  And there are probably 30 shut off valves everywhere in the basement.  Nice for isolating areas to work on them but a lot of the valves are really redundant.  Oh, and though all the piping is 3/4" hard copper, it was all painted silver.  Go figure.

? · Accepted Answer

My best guess is that he started to make a vent connection to the vent going out the window but then realized for some reason he couldn't so he just used scrap to close it off.  The funny thing is that he could have just installed an AAV at the top of the vertical pipe and called it good.

People do crazy things.  My house's former !diot put in a tall toilet tank flush valve in a short tank then let water squirt out against the wall every time he flushed for a few years before I got the place.. I had to replace the entire floor and sub floor that rotted out.

CURT D · Answer

HA!!!  The original work was done by a master...Master of Disaster that is!  You found quite an interesting bunch of projects by some misguided handyman.  I've seen vents go around bathroom medicine cabinets, but they actually continued on to vent somewhere.  All those shut off valves!  I'm usually complaining about the lack of them.  Your own mini-laundromat  too.
It's always interesting (in a scary way sometimes) how people build/fix things.  I was doing some work on a 1600's house and found the oil furnace flue pipe plugged about 85% with soot, and disconnected from the brick chimney.  The occupants were spared asphyxiation because the ancient house was so poorly insulated and sealed-  all those air leaks saved their lives.
I hate to see people get into a home only to find it was remodeled by your handyman.  I had to do massive repairs to a house that a 'builder' flipped.  Looked nice enough on the surface.  Severe long term ice dam water damage hidden under vinyl siding on the outside and scabbed 2x's covered with drywall inside.  1st home purchase by a young lady fooled by the refinished floors, new vinyl siding, windows, and roof.  Had to replace 60% of the framing sheathing on one side of that dump.  Your current find is much more interesting though.  You don't have a house, you have a museum dedicated to that plumber wanna-be!

Carroll · Answer

drains needs vented. not necessarly to the outside. did the drains work well? if so leave well enough alone. the other valve questionns also leave alone. if they are open and don't leek  they work. you might take off the valve handles to keep from future problems. my guess would be they were put in to shut off -frozen / broken pipes.

Anonymous · Answer

Change all your valves to ball lever valves, spend the extra $50.    You won't regret it.    

Half assed plumbing done by the former homeowner's brother-in-law.

crossbones668 · Answer

It is possible that this piping was used for an old gravity tank toilet where the tank was several feet above the bowl. It is also possible that the piping was used for growing dope and the isolation valves were to cut off certain hydroponic beds.

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Plumbers: what is this mystery piping?

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