How do you know without a doubt the vent is clear? Also, did this happen with the old toilets and/or, did you ever see the water in the bowl move when someone flushed the other toilet?
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I have replaced to old model toilets with Kohler Cimarron 1.28 gpf using the existing plumbing. The toilets are installed back-to-back. When I flush one toilet, water is sucked out of the other toilet bowl. I have a 2" vent and appears to be clear. I'm wondering if something different needs to be done with the actual plumbing drain lines to accomodate these newer toilets. We did replace the copper with PVC but the configuration stayed the same.
How do you know without a doubt the vent is clear? Also, did this happen with the old toilets and/or, did you ever see the water in the bowl move when someone flushed the other toilet?
Hopefully, you got some money back when you recycled the copper!
The newer toilets flush faster than the old ones, and require a proper fitting in the wall. It must be a double combination wye, NOT a double sanitary T or sanitary cross. Otherwise, flushing one can shoot to the other side and create problems as you've discovered. A wye turns the waste at a 45-degree angle down, whereas the sanitary cross, you can basically see from one side to the other. The wye directs the water down with no chance of it shooting to the other side.
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Last edited by Terry; 05-07-2012 at 04:51 PM. Reason: added picture
Jim DeBruycker
Important note - I'm not a pro
Retired Defense Industry Engineer
The water sill skip across and creates a wave of air that forces the water higher and then as it recedes, goes down the drain. The newer toilets with the large flush valves can do this on some back to back fittings.
If vented properly, no, it isn't siphoning, but if you 'rock' the boat, some will end up going down the drain as the water shoots across, sloshing the water back and forth. The wye's shape prevents it from shooting across, and means you could actually run a snake down there if you wanted to (otherwise, it would likely just go out the other toilet).
Jim DeBruycker
Important note - I'm not a pro
Retired Defense Industry Engineer
Thanks. This may be the problem. Just looked at the plumbing and it appears I have the tee/cross rather than the Wye. The toilets were installed just about a week ago and the vent was not plugged at that time. So, I'll check out this solution.
In your opinion, will this problem be resolved by switching from the tee/cross(which I have installed) to the Wye?
The "double combination Y-1/8 bend" is NOT an approved fitting for back to back installations either. Its construction, since the connections are at 45 degrees, creates TWO "3/4 S traps". The proper fitting is a "back to back fixture fitting" which is an amalgum of 30/60 bends raising the center lines to the point that "S" traps are not created. AND, it is shorter "face to face" so it fits into the installation better.
Licensed residential and commercial plumber
I guess the big question here is, is the water in the bowl siphoning or is it rocking?
I went to purchase a Toto Clayton today from a local dealer and I ran into an issue at the end of the sales process.
The sales rep / consultant asked me if the new Toto toilet is replacing an existing unit that is back to back with another toilet
I said yes, and this my be a problem because of the G max feature of the Toto. The concern is that the Toto may draw water from the other toilet every time the Toto is flushed if a Tee connection was used to connect the two toilets in the intial installation.
( the house was bulilt in 1990 in and is in Massachusetts)
My understanding is that a double Wye connection is ok
Is there a way to get some insight into what type of connection we have with out ripping open a tile floor or gambling on buying a toilet ?
Thank
T
Last edited by Terry; 05-25-2012 at 11:15 AM. Reason: spell check
You can pull one toilet, and then flush the other one. If you see water skipping across and coming up the other arm, then your fitting is allowing water across.
I have something similar in my home, and yes, it will lower the water in the bowl some. It's not a big deal.
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