I am trying to design the plumbing for a new, upstairs bathroom. My main concern is how the toilet is vented (behind the toilet and upstream from the horizontal drain). I haven't found anything in the vent section of the IPC that prevents it, but just have not seen any examples of anyone doing this way. Could someone please review this diagram (attached) and tell me if I'm way off. This is in Georgia. Thanks!

Hi EPW

Is this the only bathroom in the house? If it isn't (doesn't sound like it is), then you may be able to reduce all this venting to one 2" WET VENT.

Look up wet venting for your state and see if it is allowed. If it is, I can save you some time and money, OK? :)

Also, note that you CANNOT use a sanitary tee fitting for the toilet drain, OK? This fitting must be a wye into a 90 or just end as a 90 degree elbow (if wet vented).

Back to you...

Mark

Here's how we vent our baths in my area. Check to see if wet vents are allowed in your area. Good luck, Tom

Thanks Speedball and Massplumber,
Yes, wet venting is allowed in GA.
Got it on the wye vs sanitary tee from toilet... Thanks.

So if I understand Speedball's diagram, I don't need the 3" vent behind the toilet and can just branch my lavatory drain (and shower drain which I didn't show in the diagram) to the main 3" horizontal drain and the 2" vent behind the lavatories can be considered the one vent for all three fixtures? Thanks... just want to be sure I understand correctly... I thought there was a rule where there soil stack vent had to be the same diameter as the soil stack. Thanks!

As long as you tie the tub/shower to the lavatory drain all three will be vented by the two inch vent.This vent may be revented in the attic to a existing roof vent.

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I thought there was a rule where there soil stack vent had to be the same diameter as the soil stack.

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I think you mean the drain line since the soil stack vent and the soil stack are one. Not quite so. In my area we are mandated to have one roof vent 3" or over on as single family home. We usually vent the kitchen sink with that one. Good luck, Tom

Right, but since you already has a 3" or 4" roof penetration from the main bathroom in the house (i.e. pipe same size in basement all the way up through the roof), you can get away with the one 2" vent as I suggested back in my original post... :)

Good news for you EPW!

Ok guys, I've reworked my design to use a single dry vent from the lavatory and wet venting the shower and WC. If you would, check it out and let me know what you think. Thanks! I forgot to label the shower drain... it's the drain shown in the lower left hand corner.

I don't see my attachment on my last post there... so trying again... I think I got it this time! :)

Everything looks perfect EXCEPT no sanitary tee fitting on the horizontal... ONLY WYE or wye combination FITTINGS HERE (see image).

Make sure the elbows are long sweep elbows just like you drew them up, OK?

Nice job!

Thanks MP! Will definitely stay away from the sanitary tees. I'm going to get started on it this weekend then! If all goes well this weekend, I'll be back shortly with the next bath room! (I have two baths up stairs.. not close together... and one downstairs to do.. . then the kitchen... then the laundry room... :) Hope y'all have a great Turkey Day!. and thanks again for all the help!

Happy Holiday to you, too!!

PS: If you want this to be exactly as a plumber would pipe it use wye and 1/8th bends so you can roll your wye ABOVE the centerline of the drain and straighten it out using the 1/8th bend. You'll also roll your wye and 1/8th bend above the centerline of the drain pipe picking up the lavatories... makes these drain fittings into vent fittings... ;)

Mark