rear exit toilet

archibald tuttle

im trying to save height in a basement install where the main drain is about 18" OC above the concrete floor w/o using a pump. i see some rear exit styles with a relatively  high exit. i cant find any drawings but i assume these are s trapped in the porcelain and don't require a vacuum tight seal to a downleg of drain? 

i also notice some models with a lower exit maybe 4 or 5 inches off the floor which seems like possibly offers a better flushway path.

im hip to using pressure assisted and im going to be elevating the floor somewhat to line up whatever i choose but that starts to get into overhead clearance problems nevermind needing an access stairway using a standard floor mount.

i notice most of these units are tall pattern which might be reflective of the design space needed for the molded trapway albeit the lower the better in my application. anyone messed with these? thanks 

Jamie Hall

Remember that water only flows down hill. If your sewer main is X inches off the floor, so will the lowest water level be in the toilet bowl. And if for some reason there is a backup or surge in the main, it may well be higher...

Toilet traps are NOT check valves.

archibald tuttle

jamie, im no newton but i get the gravity thing. im assuming that the rear exit is below the toilet weir. i could put a check valve in the 3" tangent before the 3 x 4 wye. but actually the basement is not finished and i don't mind this toilet being the clog indicator, aside from being leas worried about that because the pipe above the floor is all new pvc to the street having replaced clay that had street tree sclerosis. 

Mad Dog_2

Back Outlet floor mounted Water closet. American 🇺🇸 Standard makes them.  They work fine.  Just one thing. Use a Felt/wax impregnated gasket, otherwise you'll get leaks at the horn 🤘.   Mad Dog 🐕 

kcopp

I have actually used the newer wax free gaskets on them. For good measure some silicone caulk on both mating surface helps.
Saniflow also makes a rear outlet toilet.

Danny Scully

Use a wall hung toilet/carrier. 

mattmia2

I know gerber used to make a lot of this stuff, haven't looked in a long time.

mattmia2

The tall pattern probably more has to do with them mostly being used in commercial work. i see gerber has some standard height ones as well as the carrier mount ones.

HomerJSmith

I was in the underground city in Seattle and the toilets were 4' off the ground. That's where it had to be for drainage.

You have to be careful not to place the toilet close to a vertical soil pipe or some interesting things can happen.

Intplm.

@archibald tuttle You can certainly get a rear flush toilet to fit your needs.

I have installed a "Crane" back outlet toilet. Google this. There are spec. sheets for it.
And you should not need a flush assist type.
Here is a stock picture of a back outlet toilet.
Note the closet
bolts at the wall

Mad Dog_2

A Wall Hung carrier is major reconstruction of the plumbing and the wall, but if you can do it...Mad Dog 🐕 

archibald tuttle

@Mad Dog_2 is there an advantage to wall hung. how much gain can I get in terms to keeping the bowl low to floor when I have a high sewer pipe.

i have to admit i'm confused by the units that have high outlets (other than the saniflos which flow gravity into a pumped receiver) because I don't really seem to see enough space in the casting for the pathway to be a full S trap that would siphon dry for flush. they look more like they are a cast "P" trap, whether wall hung or floor mounted with high rear exit. so i'm jsut wondering how they work . . . . that's me.

e.g.

there are no diagram links I could see that show me the internals on that toilet.

thanks,

brian

mattmia2

The wall hung have the height set by where the wall carrier is mounted. A bit easier to clean around too which is one of the reasons they're popular for commercial installations. The one you show looks like an Australian design.

Mad Dog_2

They are highly adjustable and you won't see that exit pipe out the back like in the picture.  They are pretty heavy, sit on 4 very thick 5/8 ? Bolts 🔩.  They kiss the wall, but that's just for sanitary purposes and aesthetics.  The tile  Wall does little to support it.  Go on Jay R Smith Website.  Very good product.  Mad Dog 🐕 

archibald tuttle

mattmia2 said:

The wall hung have the height set by where the wall carrier is mounted. A bit easier to clean around too which is one of the reasons they're popular for commercial installations. The one you show looks like an Australian design.

who knew, down under. should have put the link: its a "waycross" . it calls out 7.5" center off the floor for the exit (compared to 4.5 for most others) and has low bowl height (16.5 compared to 18 for many others) so that makes it the best option i've seen for keeping head clearance given the high main i'm dealing with. i just can't figure how they molded a full S trap into that footprint to maintain siphon action or can it flush just through flow?

Mad Dog_2

They work...look in to a Geberit..Wall mounted,  tank in wall takes up very little room.  A lot more practical than a Commercial Cast Iron carrier fitting and the roughing that is involved.  Geberit.  Mad Dog 🐕 

jumper

If ceiling is high enough you can sit toilet on a platform?
Better build it strong.

Intplm.

archibald tuttle said:

@Mad Dog_2 is there an advantage to wall hung. how much gain can I get in terms to keeping the bowl low to floor when I have a high sewer pipe.

i have to admit i'm confused by the units that have high outlets (other than the saniflos which flow gravity into a pumped receiver) because I don't really seem to see enough space in the casting for the pathway to be a full S trap that would siphon dry for flush. they look more like they are a cast "P" trap, whether wall hung or floor mounted with high rear exit. so i'm jsut wondering how they work . . . . that's me.

e.g.

there are no diagram links I could see that show me the internals on that toilet.

thanks,

brian

Really no reason to be confused. These toilets are most commonly made to work as required by plumbing codes. Try not to over think it.

archibald tuttle

@Intplm. overthinking is my middle name. partly that is a xxx dollar throne . . . oops almost put the price . . . or about twice as much as I usually spend for a toilet. and some of these with high outlets are meant to go right into pump out tanks which means the tank doesn't have to be in the floor.

@Mad Dog_2 like the gerberit and the similar toto but I have no stud wall, rock foundation, not going to hang anything. but i'll keep those in mind for future reference where I want that off the floor capability. aesthetics less important on this job.

@jumper I will be building a platform but the ceiling is not high so I'm trying to build it as low as possible and the rear outlet 7.5" off the floor in the pictured waycross model will save me about a foot which is enough not to hit my head!

thanks all