Toilet directly atop soil stack

[Charles2000]

Hi all,

I think this is a simple question, but after scouring this forum and others, I'm suprised at not finding an answer. Briefly, I can simplify one section of my DWV layout if I can place a toilet directly on the top of one 3" column of DWV soil stack. That is, no closet bend, just a straight drop from the flange down 8 ft. of stack through the basement.

I'm suspicious because I've never seen such a layout illustrated or discussed. I can't imagine any reason, laws-of-physics-wise, arguing against it -- but in plumbing that's how many a false step is made :-)

In detail the vertical stack would have a 3x3x2" SanY underneath to vent the toilet followed by a 3x3x2" SanT for the shower drain (already vented). At the bottom, 3X4" bushing and a 4x4x4 SanY with cleanout. This then connects through a combo to the 4" main drain line out to my septic system. This stack is at the terminal end of the main drain.

I think I'm a capable amateur, I've, er, advised and passed inspection on a larger and more complex system for a friend's place in the same county. This question regards my own (under construction) house.

Thanks for your consideration,

Charles

[hj]

The main thing is to have the vent connected properly, usually with a "Y" rather than a tee.

[Charles2000]

Thank you HJ,

I will use a 2" SanY below the flange and then take it up to the principle DWV stack above the second floor flood levels.

Is the toilet directly atop the stack a very unusual arrangement?

Cheers,
Charles

[Terry]

Is the toilet directly atop the stack a very unusual arrangement?



Yes, because normally walls are stacked from floor to floor.

You still need to vent with a wye as hj mentioned.

Below is a normal stacked wall.
http://terrylove.com/images/dwv_b2.jpg

[nhmaster]

This is one of those reasons where if every damn state would adopt the same code it would make life easier. If you were under the IPC you would not even have to worry about the vent. Beware though, when the toilet flushes it's going to be very noisy so you may want to insulate the chase with something.

[Charles2000]

Beware though, when the toilet flushes it's going to be very noisy so you may want to insulate the chase with something.

Ah. Probably why it's not common. I'll see if it's possible to fit in a closet bend if it'll help, and insulation sounds good. It will drop through the basement so should be livable in the worst case. Thanks all.

[Charles2000]

Below is a normal stacked wall.
http://terrylove.com/images/dwv_b2.jpg


Terry, I got a lot from this diagram while working out my own layout, it's tidy and illustrates several principles. I was thrown though, the first time I saw it by the 45-degree slope of the second floor toilet drain, as opposed to the usual 1/4" per foot slope. Is this a specially tolerable layout here due to the short run and the washing by the vanity upstream?

I believe I read here in another thread that low volume toilets may be changing the runoff/slope picture.

Anyway thanks for an excellent forum.

Charles

[seaofnames]

This is one of those reasons where if every damn state would adopt the same code it would make life easier.

Kind of like Canada eh? Much easier to follow code up here!

[BAPlumber]

Terry, I got a lot from this diagram while working out my own layout, it's tidy and illustrates several principles. I was thrown though, the first time I saw it by the 45-degree slope of the second floor toilet drain, as opposed to the usual 1/4" per foot slope. Is this a specially tolerable layout here due to the short run and the washing by the vanity upstream?



Charles

1/4" per foot is a minimum grade. run it all straight down vertically if you want.

[hj]

Put a toilet on top of a 8' vertical pipe, WITHOUT a vent, and then flush the toilet. The suction will pull everything within 6' of the toilet down the drain. The vent should NOT be horizontal, use a Y and place it lower.

[Terry]

Waste lines at a 45 are considered vertical.

[Charles2000]

Once again, thank you all.

I'm pretty clear about venting below the toilet with a sanY, and the potential for noise. I imagine this will end up being a straightforward and even boring install, so please pardon me if I don't follow up with pics. If it should become exciting or instructive somehow, then I certainly will post some.

Thanks again,
Charles