Losing Water Surface

**Norm R** · 02-09-2013, 09:18 AM

Hi I'm an amatuer and need a litle help. We've installed 2 American Standard Eco Fusion toilets from Home depot, I think they are AS's H2O toilet.
After flushing, the still water surface comes to rest at 9 x 8, AS design spec. However the toilet continually loses this and after 24 hrs is 5 x 3..
Have talked to AS and have received a replacement bowl, same problem. There are no leaks , I can see the underfloor connections.
As a test I placed one of the toilets over a bucket, filled it to still level and it held for 24 hrs at 9 x 8.. I presume this means the toilet is OK but could the drain system be siphoning somehow. This is not a new house, just new toilets, wedidn't notice the problem before. No change to the drains. We're are on a septic tank.
Local plumbers I've talked to have no suggestions nor heard of such a problem. We'd buy another toilet but suspect the same problem.
I have not checked the vent to see if it's plugged but there is no back-up or problems with the toilets removing any load. We only have 2 toilets and they are back to back.
This is driving us nuts any advice would be more than welcome
Thanks
Norm

**jadnashua** · 02-09-2013, 09:39 AM

Back to back toilets can do that if the fitting in the wall isn't the correct one. Older toilets had a slower flush; newer ones must flush much faster to get things out with the limited water. So, if the proper fitting isn't in the wall, some of it carries over to the opposing toilet, rocking things, and since the toilet is full to the weir (where it drains), rocking it causes some water to be drained out over that edge. Voila...the static level is now lower.

Have someone watch the opposing toilet while you flush, if there's significant movement in it, you've found the problem. Now, fixing it is harder as the proper fitting is usually bigger and harder to fit in the wall on a back-to-back installation.

Really high winds can rock the water spot, too, and cause a similar effect, but that would unlikely happen all that often unless you lived on top of Mt Washington!

**Norm R** · 02-09-2013, 10:22 AM

Jadnashua Thanks After 6 flushes the other toilet lost about an inch. Now we know thw problem it's an easy fix for us.
We'll just flush before hand when the need is a heavy load. Kind of defeats the water saving feature but we pee a lot more
often than anything else.
Thanks from both of us.
Norm

**Terry** · 02-09-2013, 11:02 AM

I'm changing the way I'm roughing in toilets now. No longer am I installing back to back toilets using a double fixture cross, and certainly not a sanitary cross.
The "skip over" pushes water out of the opposing bowl. Code will need changes in the future to reflect the changing times.

**wjcandee** · 02-09-2013, 03:02 PM

Originally Posted by Terry

I'm changing the way I'm roughing in toilets now. No longer am I installing back to back toilets using a double fixture cross, and certainly not a sanitary cross.
The "skip over" pushes water out of the opposing bowl. Code will need changes in the future to reflect the changing times.

Does a double combo wye solve this problem, or just reduce it? I know Toto says that we need to install back-to-backs with a fitting with a wye, but I think I remember someone posting here a while ago still having some issues... I have also seen commentary on here that a double-combo wye with a 1/8 bend would create an S trap (?), commentary to the effect that such an installation wouldn't pass code, and commentary to the effect that such a fitting isn't "available" in this kind of installation (which I think was intended to say that it wasn't allowed, because you can buy these fittings). Is there a better way to do it (i.e. toilets are mounted slightly off back-to-back and each is piped and vented separately)?

**Terry** · 02-09-2013, 05:23 PM

A toilet isn't vented the same way as the other fixtures. You can vent within six feet, even on the vertical below. The trapway is meant to siphon, and then the bowl is refilled after the flush.

One of my homes used the double fixture cross, and yes, pulling the bowl and watching the drain, you could see the surge from the other bathroom.

**wjcandee** · 02-09-2013, 06:06 PM

Originally Posted by Norm R

Have talked to AS and have received a replacement bowl, same problem. [...]
Local plumbers I've talked to have no suggestions nor heard of such a problem.

I'm a little surprised that neither AS or your local plumbers had the right answer to this question right at hand. Jim nailed it in two seconds. The issue is placed front and center in the Toto toilet installation instructions. Nevertheless, it's a great testament to the wealth of knowledge that Terry, HJ, Jimbo and the regular posters routinely share for free on this wonderful forum.