I have 2 adjacent bathrooms, with toilets opposite of each other. I recently upgraded one older toiled that took a minute to flush with 3.5 gallons of water to 1.2 GPF model with "aquapiston" marketing blurb. All nice and dandy, except this piston started shooting stuff up another toilet's pipe on the other side of the wall, causing it to gurgle.

This is what it looks like from below:

6-way plumbing connection

So the obvious reason is that vent pipe is one of the 6 pipes connected here (the house was built in 1960-s). Toilet 2 shoots stuff through the pipe directly into Toilet 1 drain. This blocks the vent, and causes Toilet 1 to gurgle until stuff starts flowing AWAY.

So, what creative solution can I apply in my situation to eliminate the problem, without completely redoing the junction? Preferably one that does not require custom fabrication of fittings :)

EDIT: White PVC pipe is a vent pipe for a sink that drains into a basement septic holding tank (not vented outdoors... Not sure why)

EDIT 2: One solution I considered was adding a Tee to the downpipe from Toilet 1, and connecting it to the vent above the 6-way connection. But space constraint makes it hard to add it, plus it looks like it'll cost me $100 in parts to add those 2 Tees. Is there a more economical way to add, say, 1" pipe connecting those? Would it fix the issue?

  • 2
    That is a masterpiece, yet not code compliant.
    – DMoore
    Feb 19, 2015 at 16:12
  • 3
    You could probably make enough money trading in all that copper waste pipe to hire a licensed plumber to fix it for you. Feb 19, 2015 at 18:23
  • Spitballing here - Suppose for a moment you did re-plumb all the drains. How would you do it and why? By figuring out the ideal case perhaps that would suggest a modification to the current situation.
    – Freiheit
    Feb 19, 2015 at 19:08
  • 1
    @Freiheit, I suppose each branch would merge with main stack at different heights, with wye connection, and dry venting closer to the fixture. But I don't have room to implement that.
    – Serge
    Feb 19, 2015 at 22:42
  • 1
    Are you sure your vent pipe is clear?
    – Tester101
    Jun 16, 2015 at 12:07

5 Answers 5


Move the clean out trap up to where the right toilet is,right toilet to the clean out.

This will stop cross flow from too large systems.

This should reduce cross flush and vent clogging, I think.

This looks to be the easierest think to help reduce your issues but I dont know.

That 90 in the waste after you puzzle nut can't be helping either... how far does it travel before the main stack?

Keep in mind that thing is grandfathered, touch one bit of it and it's not anymore.

Not a plumber, just a dude with a internet connection so take my advice with a grain of salt.

  • Like your disclaimer :) This solution was my first choice, but it does not line up exactly. waste line after cleanout is about 15 degrees rotated, so extending it would miss toilet by good 4-5 inches.
    – Serge
    Mar 14, 2015 at 21:04
  • I still think this is the easiest cheapest way to have an positive effect. I would look at changing the angle of that last 90 as well.
    – beast
    Mar 18, 2015 at 21:06

I have a few ideas.

The general theme of all these ideas is to do what you can to get away from that 6-way and to a set of T-fittings like more modern plumbing.

The first thing that jumps out at me is that you have a nice plug right on the end of your "away" pipe.

Would extending the pipe from toilet 2 down and connecting to where that plug is let the pressure vent any more readily or vent up rather than into toilet 1?

The second idea is probably not code and is probably a bad idea.

Add a T onto the super toilet, connect that T to the vent above the 6-way.

What I think this might do is give the pressure from the super toilet somewhere to go and vent before getting to the 6-way. At the 6-way it has "access" to all of the things, if you can let it vent sooner the pressure may be reduced before it gets to the 6-way.

Third idea - I see another plug which sort of lines up with the bathtub. Would dropping the bathtub down to that help any?

  • Thought about extending to the plug, but I have white PVC in the way (minor issue), and AWAY pipe is not aligning with the toilet (if you extend it to toilet, it would be ~10 inches to the side of down pipe). But that's my #1 option right not, even though not ideal.
    – Serge
    Feb 20, 2015 at 15:57
  • On the T-idea, I'll add another edit to a question, explaining similar option I considered.
    – Serge
    Feb 20, 2015 at 15:58

Looking at the picture looks like you need to save up some money and have it all replumbed. Or just deal with the gurgling. But I'm just a master plumber.

  • Chuckles How would you replumb this? Jun 13, 2015 at 19:00
  • Just thinking in terms of flows, toilet 1 (as labelled) flows to right, down, then left. It could go directly down and wye into the leftward "away" pipe.
    – Tim B
    Jan 28, 2016 at 17:37

@beast solution is the first that came to mind.

Another way to improve this, would be to connect vent pipe from close to each WC UPWARDS to the vend stack above the height was the wc.


Get a toilet that flushes slower thus stopping water from surging into the waste line on the other side of the cross. I'm a plumber of 19 yr. and dealing with this same issue on a new style flush system as well.

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