Vent for toilet required?

[Chucky_ott]

Hi,

Do I need a vent close to the toilet if the 3" drain is horizontal (1/4:12 slope) for 30 feet until it reaches the septic tank ? If necessary, I can put the vent at the end of the 30' run, before it hits the septic tank.

I have no access to the attic in that part of the cottage so drilling holes for a vent would be hit and miss.

Note that there is an Oatey AAV at the sink.

This is a 60-year old cottage on concrete blocks and the original 4" drain sagged and burst at one location a few winters ago.

So I'm replacing the 4" drain with a 3" drain, along with all the fixtures. The existing setup had no vents at all and worked fine for the previous owner.​

Thanks

 

[Terry]

3x2 wye downstream of the toilet.
2" x 1.5" wye or combo for the tub.
2" to the AAV and then 1.5" for the lav.

Toilets need 2" for venting and especially if wet venting using the lav.

Oatey 39017 SURE-VENT AIR ADM VALVE, 1-1/2-Inch by 2-Inch, White

The lav(s) wet vent the toilet and the tub/shower

The lav(s) wet vent the toilet and the tub/shower

 

[Sponsor]

 

[Chucky_ott]

Thanks, that helps. What I neglected to mention is that right after the long turn elbow for the toilet flange, I have a 3x3x3 WYE for a cleanout. The cleanout is not glued in yet but the WYE is. So I could go with option 1 or 2 below. Is there a preference as to which ?

BTW, any reason that a 3x3x2x2 double WYE is hard to find ? All the big box places carry are the 3x3x1.5x1.5 ? I should be able to get a 3x3x2x2 at a local plumbing supply store.

 

[Chucky_ott]

I think I answered my own question. Since the toilet needs to be downstream of the other fixtures, option 2 would be the one to use.