How far can my toilet be from horizontal Main Drain?

[THESHACK]

From Ontario Canada
I'm building an off the grid home completely alone. I need some advice on a toilet drain length.
I don't think I need to vent the 60"toilet trap arm but man is it hard to confirm. I can't see how a syphon can be generated but maybe there is a scenario I'm not considering.
Main drain is 4" and runs just below the joists under the main floor (approx 36' total length 1/8" per foot slope).
I believe I can tap into the main drain with a horizontal tee (4x4x3 up) off the tee at 90 degrees, with a straight run between the joists for 60" -65" (1/4"per foot slope) then up with another 90 degree up terminating in the 3x4 floor toilet flange. Distance between the top of the toilet flange and the top of the 4" main drain pipe is roughly 16"
The 4" main drain is vented to the roof with 3" pipe. The vent connection tee is right beside the toilet tee in the next joist run space down stream of the toilet connection (vent stack to toilet drain connection roughly 16" on center)
I'm thinking/hoping I don't need a vent in the toilet drain line? The thing that is throwing me off is I'm not connecting to a vented vertical drain pipe which I know would be no problemo . Help please and thank you?

 

[Terry]

We always vent within fix feet of the toilet. This can also be done with a tub, shower or lav if they are vented, what they call a "wet" vent. We bump the wet portion up to 2" for that purpose.

Any fixture coming off of a horizontal line is a wye or combo, not a santee. The santee is not directional when poop lands far below, it spreads out both directions. Not a good thing.

I prefer to wye off a main line or do something like this so that I can use a 90 bend and force the waste downhill.
Here, the lav run with 2" wet vents the toilet and the tub.

 

[Sponsor]

 

[Reach4]

I can't see how a syphon can be generated but maybe there is a scenario I'm not considering.

Toilet venting is not about avoiding siphoning. You want siphoning.

I think the purpose is more to not have the slug of water having to fight against pressure or to have some other thing, like a laundry standpipe, generate a vacuum that sucks water out of the bowl.

 

[THESHACK]

We always vent within fix feet of the toilet. This can also be done with a tub, shower or lav if they are vented, what they call a "wet" vent. We bump the wet portion up to 2" for that purpose.

Any fixture coming off of a horizontal line is a wye or combo, not a santee. The santee is not directional when poop lands far below, it spreads out both directions. Not a good thing.

Appreciate the info. Yes I understand a wye would be best for a directional push but in this instant makes my plumbing holes through the floor much more complicated and harder to seal and insulate. A santee allows a simple round hole up through the floor. The "drop" from the bottom of the 3" line to the bottom of the 4" main drain is only 11" and I do have double vanity sink drain upstream of where the toilet connects so I'm hoping this also helps wash the solids down the pipe. I'm not sure what a "combo" is but I'll look into that
You seem to be saying I can also get away with having no vent on a sink etc if I use a larger dia drain arm and I keep the slope of the drain arm and length of the drain arm to a level that keeps the wier below the level of the top of the pipe where it connects to the vertical portion of the drain pipe into thee main drqain. I'm assuming the bigger diameter allows for air in the pipe. My understanding was that you could run 6-8' trap arm lengths but assumed you always had a vent on the up side of the fixture

 

[Terry]

The sink needs venting. The vent does stay on the high side of the trap arm.

The toilet siphons, and the bowl gets refilled from the tank. It gets vented differently than the shower, tub or sink.
I would not count on the bathroom sink to clear out poop from the lines. I've had to cut lines to clear them before.

 

[THESHACK]

Toilet venting is not about avoiding siphoning. You want siphoning.

I think the purpose is more to not have the slug of water having to fight against pressure or to have some other thing, like a laundry standpipe, generate a vacuum that sucks water out of the bowl.

I think what you said is absolutely right if you're having to fight a pressure, water will back up, fill the pipe and create a syphon as the"slug" drains. The vacuum you mention is the definition of a plumbing syphon - you're sucking the water out of the toilet. I think my 65" line is OK but I can't find anything online that supports this clearly to me.

 

[Reach4]

I can't find anything online that supports this clearly to me.

There are two factors: does it work? Logic applies to that. I think yes.

The other factor is will it meet code? Does "off the grid" also mean it is not going to be inspected?

 

[THESHACK]

The sink needs venting. The vent does stay on the high side of the trap arm.

The toilet siphons, and the bowl gets refilled from the tank. It gets vented differently than the shower, tub or sink.
I would not count on the bathroom sink to clear out poop from the lines. I've had to cut lines to clear them before.

Fantastic.
I have something similar to one of your sketches. I modified it to should a better rendering of what I have.
The only thing I haven't shown well is the 4" main pipe is about 8" below the plane of the toilet drain arm so basically connects with a santee
do you think the fact the vent pipe is 16" down stream of the toilet connection will be problematic?

 

[THESHACK]

There are two factors: does it work? Logic applies to that. I think yes.

The other factor is will it meet code? Does "off the grid" also mean it is not going to be inspected?

Seems like it'll work but again I'm not 100% it will meet code and unfortunately off grid doesn't mean code won't apply. Code applies to plumbing just doesn't strictly apply to electrical because it will not be a grid tie home.

 

[Jadnashua]

Wouldn't a 45 and a wye work? A santee is not good for draining a toilet.

 

[THESHACK]

Wouldn't a 45 and a wye work? A santee is not good for draining a toilet.

No, unfortunately I don't think so. The top of my 4" main drain is is located about 2" below the floor joists (floor is sealed and insulated) and runs against ( parallel) to the main beam. The configuration of a wye would require a much bigger hole configuration up through the plywood and then make sealing it up very challenging (the wye arm on the diagonal is what would be penetrating the underside floor). As an off grid home it is imperative to maintain an extremely tight seal in order to maintain the lowest energy/heat loss. Going up through the floor with a simple round hole off a santee is very clean and easy. I'm thinking a street 45 into the vertical leg of the santee to keep things tight to the top hole of the 4" santee might give me enough "push" to get water flowing downstream as it enters the main drain. Keep in mind I only have 14-1/2" of space between the joists to fit whatever drain configuration I end up with. So config would be run a street 45 off the top off the santee parallel to the main drain then a 90 long turn off this 45 to point it towards the toilet arm which would follow the joist. The other restriction is all this has to fit in between the joists which are 11-1/4" tall (2x12)