Toilet directly atop soil stack

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

drain

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

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

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

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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.

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.

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

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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.

Terry said:

Below is a normal stacked wall.

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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

nhmaster said:

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

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

Charles2000 said:

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

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

toilet

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.

Waste lines at a 45 are considered vertical.

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

hj said:

toilet

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.

Click to expand...

I see this is a old conversation but it's almost identical to my situation and I was hoping HJ could provide a little clarity.
The only difference in my situation is that I'm going to be slightly offset from the stack (I will go from the WC flange to a 45 to a street 45 and into the stack) and instead of having a shower drain join the stack below the WC vent I will have a lavatory sink (also separately vented).

HJ wrote "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."
Are you saying not to do this or just to make sure it's properly vented if I do?
I was going to put a 3x3x1.5 sanY directly under the second 3" 45° below the WC that would serve as the vent connection for the WC. Below that would be another 3x3x1.5 sanY that would be the drain connection for the lavatory sink (I am aware the sink connection should be a sanT, but in this case the connection runs about 2' up at a 45° before going horizontal and the sink is vented separately above its fixture arm).

1)Other than the loud flushing noise in the basement below (it will be behind insulation and I'm not concerned with the noise) is this a acceptable instalation?

2)Is it ok that the WC vent pipe upstream if the 3x3x1.5 sanY runs horizontal under the floor about 3' to get to the closest wall before it can go vertical?

3)Seperate question: Is it ok for a vent pipe (in this case a 1.5" kitchen sink with garbage disposal) to run uphill away from the sink, than downhill towards another shared vent stack?
In this situation any water in the pipe running uphill away from the sink would drain back towards the sink and after the "peak" would drain downhill towards the vent stack witch would then drain into a washing machine drain.
In short all the water that may accumulate in the vent pipe will gravity drain either towards the sink it serves or the washing machine it shares a vent stack with. No water will be able to sit in the pipe. To be clear, it is a vent only, not a wet vent, so any water in it would be from condensation only.

I'm in a similar situation. The inspector just turned mine down.

I'm in a similar situation and would be interested to hear the opinions on it. I'm trying to figure out the best alignment for my DWV for a 3/4 bathroom and could also have my toilet drain drop straight into the main drain line and then Wye off to the main stack.

We are allowed wet venting up here, so this would also allow my plan to be more spread out.

Also, how far down is the most you would go before putting the Wye in?