TOTO Eco-Drake "back-to-back" installation please HELP

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wms

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Hi everyone.

We're in the final stages of a bathroom remodel. A large, full bathroom was remodeled into two 3/4 bathrooms by a contractor.

The problem I'm having is the dreaded siphoning between the two Eco-Drakes that are about three feet apart (side by side) separated by a wall. I explained the problem to the contractor and asked if he had used the combination wye noted in the TOTO instructions.

The response I got was the wye had to be installed horizontally due to access restrictions and it was causing backwater. If I could not live with it, he would install two 43901 3" ABS backwater valves.

My questions are will the backwater valves really solve the siphoning problem? What, if any, are the negatives to adding backwater valves at the toilets? Should I tell him to leave it and hire a "real" plumber to do the piping correctly?

Thanks in advance!
 

WJcandee

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Yours is a slightly-different issue than the one shown in the instructions. The situation there is that you have a vertical waste stack (which provides venting) wherein you get sloshing across if you use a sanitary cross, which pushes air or water up towards the other bowl which then recedes and draws some water from the bowl with it. In your installation, it sounds like he piped each toilet to one side of a horizontally-laid wye, with no vent before the attachment of the other toilet. So what you have is a flat-out siphon of the opposing trap when you flush one toilet. I'm not a plumber, but I'm reasonably-familiar with the codes, and they typically require that drains from other fixtures must enter downstream of the toilet's vent. So my marginally-educated view is that at a minimum there should be a vent upstream of where the second toilet connects, which would prevent toilet 2 from siphoning toilet 1. Similarly, a vent connection for toilet 2 before it enters the main drain should reduce the possibility that toilet 1 would siphon toilet 2. But I'll defer, of course, to any pro who wants to weigh in here.
 

wms

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Thanks for your reply Candee.

The 'in-line" toilets sit between a sink and shower. I'm pretty sure there's a vent on the shower and I think there's a vent on the sink.
 

Terry

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If you flush one, and observe the other bowl at the same time, you will be able to tell if it's crossover pushing air into the other bowl.
I see some of that in my home, and I'm sure the plumbing is vented. Doesn't help much though when the water skips past the venting and into the closet arm.
Trust me. There are ways to do this right, but the codes haven't caught up with the new science. I have inspectors calling me about this.
I won't put two toilets on a fixture cross. Doesn't matter if it's vertical or horizontal. It doesn't work with the new toilets.

Well, you can get by with it, but it's not how they should be either.
 

wms

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Yes, that's exactly what I see. If you flush one multiple times, it siphons all the water out of the other bowl making it necessary to then double flush.
So, will the backwater valves work with no ill effect? There is no option to re-arrange the toilets.
Any other suggestions?
Thanks!
 

Reach4

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Yes, that's exactly what I see. If you flush one multiple times, it siphons all the water out of the other bowl making it necessary to then double flush.
So, will the backwater valves work with no ill effect? There is no option to re-arrange the toilets.
Any other suggestions?
Thanks!
Not a pro.

Backwater valves here seem weird. I see that as a clog point. And if the backwater valve were perfect, how does that keep water from being drawn out of the bowl? The water direction in that case is the same direction as for a normal flush. How are they going to install backwater valves easier than making the plumbing normal.?
pix_3.png
Is this a rough representation of your situation? (red pipes/fittings, green walls? If not, you can modify the picture with Paint or your favorite drawing program.
 

wms

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Thanks Reach4.
I have not seen the plumbing myself, but from what my contractor described, yes, your representation is accurate.
I'd love for the toilets to be plumbed "correctly". I think the backwater valves are supposed to prevent water/air from going back up the other toilet and siphoning the bowl water out. I am just a DIY homeowner and have no experience with waste drainage, backwater valves, etc.
We didn't pull a permit (shhh!) so it doesn't necessarily have to be to code for inspection. If Terry wouldn't mind explaining a few ways to do it right without considering "old" code, it would be greatly appreciated. I just want these bathroom Eco-Drakes to perform fantastically like the one in our powder room.
Thanks All!
 

Reach4

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You might show that sketch to your contractor to see how it agrees with his impression.
 

wms

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Yes, that's what he piped while the floors were open. Now the floors are closed and tiled. There is access under the raised foundation, but it's a long, tight crawl and he's apparently claustrophobic.

Not sure how he intends to put in backwater valves, but after reading up on them, not sure they would stop the siphoning. I think enough air and water could "whoosh" through to the other toilet before the gate/flapper closes. Don't want to be charged for work that might complicate things and still be ineffective.

Terry, could you please tell us the ways to do this right?

Thanks All!
 

Terry

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Or you could just get used to it.
My home does a similar thing. Even if I have to flush with less water in the bowl for one, it still uses less water than what I took out of here.
If you flush those evenly, you really don't notice. If you flush one several times and haven't flushed the opposing bowl, yeah you notice that.
I don't think what you have is a deal breaker.
And I don't blame the contractor, this is all new, and it's going to take time to upload into the ozone what is needed now. There is always a delay in the teaching moment.
Things happen, discovery, and then solution.
 

OneLeash

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We recently purchased two Toto Eco Drakes for upstairs. We love the one downstairs installed 4 years ago.

Okay, so we installed the new hall bathroom toilet May 31. Works great. The existing toilet on other side is 21 year old Kohler Wellworth Lite 3.5 gpf. No issues with siphoning. So we planned to install the other Toto Eco Drake in place of that Kohler tomorrow. However I happened to read that "Important" message about the WYE vs sanitary tee. Our home was built in 1963, so I'm sure it's sanitary tee. I called Toto and the guy said there might not be an issue or just minimal siphoning that won't affect the toilet's integrity. He said they have to put that warning to cover their own tail, so to speak.

If there is no issue between the new 1.28 Toto and older 3.5 Kohler back to back, is that a good sign that there might not be with another new Toto?
 

Jadnashua

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The way that the newer toilets can work with much less water than the older ones is to engineer a way for the water to exit faster, which carries away the waste. So, it's not certain that if it works now, it will still work if you replace the other toilet. It all depends on the exact layout of the waste lines.
 

Reach4

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OneLeash: Have somebody flush the Toto while watching the water in the Kohler bowl. Is there a disturbance? I would expect the disturbance to be larger with the new toilet. If there is no disturbance or a barely perceptible disturbance, I predict you would be OK. This expectation is not based on experience.
 
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OneLeash

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Reach4-----We've flushed the Toto and watched the Kohler at the same. Absolutely nothing happens. I've done this multiple times and there's never been any disturbance in the Kohler whatsoever. So, I'm hoping that there won't be an issue or very minimal with another Toto in its place. We'll find out tomorrow! :D I'll report back!
 

OneLeash

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By the way, why would there be a larger disturbance in another Toto? I mean, isn't it the quick flushing of the OTHER Toto that causes the siphoning? Why doesn't it siphon any water from the Kohler? It's sharing the same sanitary tee. Just curious why another Toto changes this. Thanks!
 

Reach4

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My thinking that the older toilet has more water sitting in it than the new. So if the new toilet has half as much water, I would expect a given amount of cross-over energy to affect the new toilet twice as much. That might be 0 x 2 = 0, or it might be (almost perceptible) x 2= (barely perceptible). Anyway, I expect things to be OK. Just speculation. If you flush the same toilet 10 times in a row, I wonder if you will be able to spot any drop in water height in the other. Dunno. I am hopeful, and predict, there will be no noticeable loss.
 
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OneLeash

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Thank you, Reach4. I'm keeping a positive outlook because I really want all three of our toilets to be Toto Eco Drakes 1.28 gpf. Also, the new toilets are high profile which is nice for aging knees. That was a pleasant surprise since I didn't realize it when I ordered them online through Home Depot.

Fingers crossed that it works in our favor.
 

OneLeash

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We did it. We got the 2nd Toto in successfully. And, when we flushed both back-to-back toilets a few times, very little water was siphoned out. I just made sure to flush again to make sure the water level was at its peak. And flush evenly. (Both toilets) I'm assuming if it hasn't siphoned more water out during a flush, it won't change. Of course, we can't keep flushing the same toilet over and over without doing the same with the other one to even it out, I assume?
 

Reach4

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We did it. We got the 2nd Toto in successfully. And, when we flushed both back-to-back toilets a few times, very little water was siphoned out. I just made sure to flush again to make sure the water level was at its peak. And flush evenly. (Both toilets) I'm assuming if it hasn't siphoned more water out during a flush, it won't change. Of course, we can't keep flushing the same toilet over and over without doing the same with the other one to even it out, I assume?
Nice. Let us know when you learn more about repeated flushes of the same toilet.
 
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OneLeash

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Nice. Let us know when you learn more about repeated flushes of the same toilet.

Both toilets have been flushing perfectly. I don't even see any siphoning now at all. And I've flushed one toilet more than once. I'm thrilled that they're working. Not sure why, since I heard there would probably be an issue with a sanitary tee vs WYE. I'm not complaining! :)
 
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