One toilet flushes the other

[IdaSpode]

I have two toilets, back to back. The toilets are both "Skyline Champion 4" with the huge flush valve, the one they show flushing golf balls.

I have to say, they do as advertised but maybe too well...

Flushing the upstream toilet will siphon water from the bowl of the downstream unit. After about two or three flushes, the downstream bowl is almost emptied out, enough so that sewer odors are detectable. In reverse, the downstream will also siphon from the other, but not nearly as much. The bathroom drains are the last on the line with a direct, straight shot to the septic tank, line is clear, vent is clear.

The drains come down from the toilets then into 90* ells and into a 4-way Tee. The 4-way also has a 2" side inlet for shower and bath drains (also back to back) and the vent stack. The sink drains run in the wall to the vent stack above the floor line.

Any ideas on how I can remedy this situation? The only thing I can think of would be to install at least one P-trap, (maybe two) between the Ell(s) and the 4-way Tee.

The system is glued ABS pipe and space it tight, but I may be able to rube goldberg the P-traps in using no-hub fittings.

Thanks!

David

 

[johnjh2o]

That is a common problem with Toto and American Standard toilets when piped with a DBL fitting. Toto even has a warning about it. I'm not sure if American Standard has the same warning but the should. There is no fix other then re-piping it. Putting additional traps in the line is against all plumbing codes. Plus it won't work but it will give you more problems.

John

 

[IdaSpode]

Yeah, once I started thinking about the traps I figured it wouldn't solve the problem and would likely create more, as you pointed out.

How would you suggest "re-piping" it? Take the downstream drain, isolate it from the 4-way and connect to the main line further downstream?

Thanks!

David

 

[johnjh2o]

David could you take a picture of the way it's piped? I may be able to point you in the right direction.

John

 

[IdaSpode]

Thanks for looking.

The 2" pipe coming in from the right is the kitchen drain.

The two pipes to the Y are shower/bath drains.

 

[johnjh2o]

David is there a vent on the tub and shower other then the side outlet DBL TY? From what I'm seeing it can be done but it will take some work. But I need to know about the vent.

John

 

[IdaSpode]

No vent(s) that I can see, looks to be direct from drain into the Y.

 

[LiQuId]

the bungalow fitting ( sidfe outlet t-wye ) makes the shower and bath stack vented IF they are ther highest fitting on that pipe ( no fixtures connected above ) and considers the Toilet now to be wet vented through the fitting also. How are the lav's Tied in ? we typically would run the side outlet to as lav and then branch off for a tub or shower.

I would suggest that a wet vent serve one of the toilets, this could be piped to a lav or run just as a vent. The issues I see are the back to back Toilets meeting on a t wye. and Though a minimal issue the 90 on the bottom of the side outlet t-wye is likely also adding some turbulance.

do you have seperate shower and bath? It looks like the 1 1/2 pipe on the branch could serve a lav.

 

[johnjh2o]

Liquid his problem is with the new American Standard toilets, they can not be piped back to back with a DBL fitting. His problem is not uncommon with these new toilets. There having the same problem with Toto. They flush so fast that one will actuary splash back up into the other. I'm not sure of the exact number but I believe there must be at least 30" between the closet bend and the DBL TY. I plain on doing a drawing for him but I don't have the time tonight.

John

 

[LesF]

FYI, this might be helpful.
I just had a Champion 4 toilet installed (thankfully, by a professional) when I updated my bathroom.Although I did not install it back-to-back, there is a warning note in the American Standard installation instructions. I'll re-type it here (I have no other way to attach it):

"NOTE: BACK-TO-BACK INSTALLATION
Depending upon your plumbing and venting conditions, the flow from the Champion in a back-to-back installation may create a vacuum on the system and draw water from the opposing bowl. The National Standards Plumbing Code prohibits the use of a cross fitting for drainage as throw over is possible. The code does approve a directional "Y" style fitting with proper venting to direct the water downward and away from the other toilet."

There are also pictures of a "Y" and a cross fitting to illustrate the point. I have no way of including them here, but from the photos, it looks like the OP's toilet is basically plumbed with a cross fitting.

Hope this helps.

 

[IdaSpode]

Thanks Les,

I searched for my model and came up with the same "note". I blame the installer, me... Who reads the installation instructions anyway?

I'm not that familar with large drain fittings but it looks like my "T" is at least somewhat "swept". I'll have to look at alternate types of fittings, maybe there is something better.

David

 

[kopexblue]

Thanks Les,

I searched for my model and came up with the same "note". I blame the installer, me... Who reads the installation instructions anyway?

I'm not that familar with large drain fittings but it looks like my "T" is at least somewhat "swept". I'll have to look at alternate types of fittings, maybe there is something better.

David

Try an aav on the pipework to cure the syphonage

 

[LiQuId]

Try an aav on the pipework to cure the syphonage

Just remember that you cannot put these in places you cannot access.