Can I install toilet vent in vertical section of pipe below toilet?

[dayster]

Howdy,

I am doing a new toilet installation. The 4" waste pipe will drop from the toilet flange straight down a couple of feet, then through a 90 degree bend, then has a few feet of horizontal (on a slope of course!) run to the stack.

I have a 2" vent ready in the vicinity, and will connect the vent to the waste pipe with a 4x4x2 sanitary TEE.

Question: I could install the TEE either in the vertical drop pipe, above the bend, or immediately after the bend in the horizontal section of the waste pipe.

Is either one better? I think the vertical option is best, as it puts the entry of the vent air as close to the toilet as possible.

Many thanks for any advice!

Dayster

[leejosepho]

Mechanically, you do not need to vent that line at all since there is absolutely no way a toilet can ever release enough effluent rapidly enough to fill a 4" line and siphon its own trap. As long as the plumbing below the toilet (4") is larger than the opening in the bottom of the toilet (less than 3"), no additional venting is mechanically necessary. Nevertheless, I would go with your vertical option unless its installation would be extremely difficult.

[Terry]

You can use the vertical postition or the horizontal. Either way, I would consider a wye fitting for the vent. If the vent is within six feet, you are fine.
Venting the toilet helps to prevent other fixtures from siphoning dry.

[dayster]

You can use the vertical postition or the horizontal. Either way, I would consider a wye fitting for the vent. If the vent is within six feet, you are fine.
Venting the toilet helps to prevent other fixtures from siphoning dry.

Many thanks Terry and leejosepho.