Hi-
We're completely renovating our 1962 ranch house in northern California - adding a half-bath and moving the kitchen. The existing cast-iron drain lines had a couple of spots where the galvanized vent tied to it had rusted out, and a crack in another spot - and additionally, ABS is much easier to add our new connections to, so we decided to replace all of the cast iron with ABS.
I'm having an issue under our master bath, which backs up to our kid's bathroom. Both toilets are back-to-back, and the crawlspace under the house is pretty tight. At first, I used the incorrect fittings to tie the toilets to the main 4" drain line, which runs directly underneath the toilet waste stack.


I now have the correct fittings, but they're about 3" too tall to fit in the required space- and I can't dig out and sink the 4" drain line any further without compromising the slope on the drain line.


Anyone have any bright ideas?
Thanks!


And now I can't seem to reply, so let's try editing my previous post...

HJ, From all my research, the old-style double fixture tee is incorrect for new low-flow toilets, and you have to use the combo wye. The install manuals (i checked multiple makes, not just the Toto we're installing) even say so.


With the fitting in there now, and the 1.28gpf toilet in there is, shall we say, "underperforming", even with only the one toilet in place, and the other flange with the test cap still in.
(We're doing this the stupid way, and living in the house while we renovate)

N.C. Plumber and Packy, Thanks for the input, I'll see if I can figure something out with street 45? fittings, and a proper 45? wye further down into the main drain... I'll post back if I can't figure it out.



Edited 1 times.

if you build your comby with a 4 x 3 wye and street 45 that should help some.



Edited 1 times.

You could use a st.45 in the bottom of the double wye, turned 90 degrees to the main drain line. Then place a 4" X 3" wye further downstream, rolled over on a 45 to catch the toilets.
Instead of a double wye, you could use a back to back fixture fitting, that should give you enough room to drop vertically into the main drain.

It is not a question of "he could use a back to back fixture fitting", but rather he SHOULD use it. The double combo is still the wrong fitting.

your first picture shows a couple of 3 x 2 sanitary tees in the horizontal drain. by code , those are supposed to be "Y"s..
as for the toilets..
i would move the "Y" downstream a few feet. put a street 45 into the branch to bring it back to horizontal. put a short piece of pipe then put a "Y" and street 45 looking up to catch the first toilet. next put a "Y" and street 45 looking up to vent both toilets and last put a short piece of pipe with a 90 for the second toilet.