[Greenbuilding] 2" drain line for a 0.8gpf toilet?

[Reuben Deumling]

Maybe I'm all wet, but this conversation reminds me a little bit of the Big
Three in the early sixties blowing off Yutaka Katayama. Why on earth would
anyone prefer fewer than eight cylinders?


There are, after all, reasons someone might want to avoid that 3" pipe
running through walls and basements and around corners. I tend to fiddle
with houses that were built before indoor plumbing, and the bulky cast iron
lines that were added later have a way of interfering with just about
everything, not to mention remodeling. I've gone to considerable lengths to
accommodate the still large ABS successor pipe for upstairs bathrooms and
under slabs. To think that something smaller might be just as good or even
slightly better is (to me) tantalizing.

On Sun, Apr 24, 2016 at 8:03 PM, John Salmen <terrain at shaw.ca> wrote:

> I can echo Joe on this and the cadet is a good design as it has restricted
> flow to provide a scouring action - and that said oversizing pipe can be a
> problem for the same reasons - but current designs are based on 3" and
> perform well and that is where I would want to sit 'so to speak'.
>
> -----Original Message-----
> From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org
> ]
> On Behalf Of Joe Killian
> Sent: April-24-16 4:47 PM
> To: greenbuilding at lists.bioenergylists.org
> Subject: Re: [Greenbuilding] 2" drain line for a 0.8gpf toilet?
>
> Reuben,
>    The American standard Cadet 3 toilet (a popular and very good unit) has
> for it's exit aperture:
> "Fully-glazed 2-1/8" trapway with 2" ball pass"
>    If there's a stoppage anywhere, you'd want it to be AT the toilet, not
> somewhere down the pipe.  So a pipe substantially larger than the fixture's
> exit aperture would be advisable.
>
>    With a macerater, a 2" pipe is acceptable, afaik.  ...If you wanted to
> trade that complication for the smaller pipe.
> Joe
>
>
> On 4/24/2016 3:29 PM, Reuben Deumling wrote:
> > I have long wondered whether or when anyone would dare diverge from
> > the 3" standard drainline diameter as we get toilets that use less and
> > less water per flush.
> > Interpolating from this chart:
> > http://www.mpwmd.net/rules/Apr2008/pdfs/RegII/rule24_table1.pdf
> > I see that in terms of fixture units, a 0.8gpf toilet is now at 1,
> > which puts it comfortably within the same class as sinks, which as we
> > know do not require anywhere near a 3" drainline. So..... does anyone
> > on this list know if there is any movement toward allowing a 2"
> > drainline for a 0.8gpf toilet? Or whether there's been any testing of
> > this configuration?
>
>
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