1. If you know of any like you describe in use,talk to the homeowners to see how they like it. If you don;t know of one like it in use just figure there;s a reason.

"... can I extend the vent pipe up, say 12-24" from the elevation of the drain and then 180 the vent back down through the floor plate to a common vent pipe running under the pier and beam home for the bathroom sink, toilet, wash machine, and kitchen sink?"

No.

The plumbing codes weren't written to be mean, they were written to save lives through sanitation and venting deadly sewer gas. You sound as if since the code won't be enforced, that you're somehow exempt. You are not; particularly if you have children.

Do your job properly please.

It won't kill you to look at a plumbing vent penetration on your roof. Not looking at it may.

Hire an actual plumber. Before you kill yourself and your family both.

Where I live there is something called the single stack system where all plumbing in that area is tied to a single large vent. But that vent goes up. You can't vent gases down through a 180 degree turn.

Ok, thanks for your input but I can see I need to clarify my concept. I think some quit reading too early....

"...can I extend the vent pipe up, say 12-24" from the elevation of the drain and then 180 the vent back down through the floor plate to a common vent pipe running under the pier and beam home for the bathroom sink, toilet, wash machine, and kitchen sink? The common vent pipe under the home would have a single riser in an exterior wall and vent about 8' high on the east side of the house.

I think the only thing unusual that I am asking for input on is that normally the vent pipe would continue up from each fixture. I'm proposing an under-the-home common vent pipe with a single riser from the common pipe to vent outside (certainly not under the house). I would have to go DOWN from each fixture with the vent pipe to join the common vent pipe so I proposed a short 12"-24" rise of the vent pipe from each fixture to prevent water entry and a 180 turn down to the common vent pipe.

NO you can not do that. You do not understand plumbing, or venting. Water runs downhill, while gases rise. You would be creating a health hazard by trying to make water run uphill or gasses run downhill. The entire purpose of a P trap is to keep the deadly sewer gasses out of your house via a section of pipe with water in it as a blockage to that. It's why S traps are prohibited, as they siphon the water out, and allow gases to enter.

Perhaps I should add that, with exception of the main vent pipe, which would not have a 180 degree turn in it, each of the fixtures, sinks, shower, and commode need an air draw to protect water in the p-trap from being siphoned out. They make a one-way vent that may be used when there is no way to vent to the outside. I am not a fan of those so my concept is largely, if not entirely, an air draw source and only the main (common) vent pipe would vent gases from the sewer system.....since it would be open to the septic tank and open to the outside vent stack. I should have created a diagram I suppose.

Several people have been very clear with you - and I'll add to the chorus: You clearly don't understand the purpose of plumbing codes, and rather than do it properly, you are trying to get us to go along with this nonsense. No. No responsible person on here should have any part of that.

Hire someone to do the job properly - to code - even if there won't be a code inspector there. There is a really good reason to do it according to code - it's not there just to make your life difficult.

What's more - anyone who lives in this dwelling, and anyone who purchases this property in the future, has the expectation that the work that's hidden behind the walls and under the floor was done properly and will not make them sick.

After doing more research, I still believe I am being misunderstood.....but no need to keep beating the dead horse. I appreciate the time you guys have spent trying to save my life.

Ultimately, I am trying to keep from using one of these (Sure-vent photo below) in areas where I need to have ambient air ENTER the sewer venting system......I could use a Sure-vent at each location I am proposing to connect to a common vent (two sinks and a shower). Instead of using a Sure-vent (which I have used before and believe they are not so sure), I am proposing to run a vent pipe from each sink and the shower to a common vent pipe under the house. The common vent pipe under the house will have a riser to vent gasses either out a side wall or through the roof. The standard P-trap at each sink drain (as also depicted in the photo below) and the shower p-trap will prevent entry of gases from the sewer into the house.

It is YOU that is completely misunderstanding basic plumbing. VENTS GO UP. ONLY UP. NOT DOWN. You can not have a vent pipe that goes down. The gas cannot follow. Sewer gas is explosive, as well as can kill you, just from being in your house.

How is it that you persist in wanting to kill your family? Is it intentional? Do you have a major insurance scam planned? A side piece and no one will give you a divorce? Someone gonna find out you married your sister-cousin?

If it were just you, sure, go ahead and gas yourself, or blow yourself up.

This type vent benefits me in my remodel since I apparently can have a common vent UNDER my home rather than need to drill up through two floors for each fixture to a common attic vent.

Just follow code and you will be fine.

John 9a:

Loop vents are allowed at the discretion of a local AHJ inspector, and is usually based upon the cost effectiveness of standard venting vs. loop venting. Something like a sink in a kitchen island that's too far from a wall comes to mind.

You've stated that that you "...don't have to comply with any city codes, as I'm in the country". If you can cost effectively vent properly, I'd suggest you do so.

I would suggest looking up your state's Plumbing Code, which will be IPC, UPC, or state proprietary. Whether anyone checks your house is of no matter; it is for you to read along to understand how plumbing works, is sized, routed, and to install it so it does. Otherwise, you might as well use a port-a-potty and the river to clean dishes.

For instance, if you were to use an AAV, ("Oatey Sure-Vent" is one brand) there are strict limitations on it's use, say for a minimum dimension above a branch line. As well as for island venting, say being limited to sinks and lavatories. There are distances from vents that might help you, say a toilet being within 6' from a vent stack, or say using wet vents.

You do not have to run an individual riser up through the 2nd floor for every fixture, but you certainly will need at least a main stack vent. Your anxiety about a roof penetration seems to be overblown to try so hard to use a horizontal vent under all the fixtures, which when going out the sidewall would have to extend above the roof 10' anyway.

Edit: Also to answer your original question I believe an upside down P-trap would be like an S-trap, which is not allowed.

And it seems from other threads you have progressed to tiling in the bathroom, so don't know if you planned on doing rough plumbing after finishes for some reason.

Maybe we should discard the "upside down p-trap" terminology. The diagram above of the loop vent is what I had in mind when I said upside down p. The part of the air vent that goes up and then down is what I had in mind.

I have begun tile work but have left the water supply wall off the shower build until delivery of the shower pan...took 5 weeks but no big deal as my remodel job is taking a second row seat to other issues. I hope to get plumbing started now.

And this, ladies and gents, is why you NEVER purchase a DIYer’s house.

Y'all are like a flock of chickens....when one squawks, the rest come running to pile on.

I asked about a concept and all I got was NO, NO, NO, and I was trying to kill my family (I'm single so maybe I already succeeded in that respect).

After seeing the comments, objections, and so-called reasoning that gasses can't be vented downward....not true....and seeing nothing in the mess that logically rendered my concept unsafe, I decided to do more research....and found the term I needed (loop vent) for the concept. It's ABSOLUTELY code to vent a kitchen island and even a dishwasher with such a vent. I may be going astray of the letter of the code by using the concept for a bathroom sink but the principle is exactly the same. If the principle of the vent in a bathroom sink is different from an island sink, please constructively explain why.

Yes, I finally ran short of patience!

You don't get to pick the answers you get here.

That's true and I appreciate folks trying to help. By one means or another, I found the information I needed so that was the ultimate goal. Interesting how sure everyone was I was going to kill myself and my family and referring to code...and it turns out my concept was code in at least some applications. Perhaps I just did a terrible job describing what I wanted to do, otherwise I have to say the quiet part.

Houzzers always come through whether or not it's what the OP wants to hear. It's what makes the site valuable.

John is single? Whoudathought?

I have several Studor vents in my built, but also a single vent pipe that vents a few of the showers / tubs - now you have me wondering how it all connects as I am on a slab. I will look and report back!

Sometimes reality and cold hard facts aren't what we expect but I expect folks to stick to what they do know about...or add qualifications...and not pile on me with a bunch of incorrect information....that's precisely what some/most did above. That's OK, I'm a big boy and I can sort out the mess but I have seen more and more abusive and snarky comments in recent months/years. Gardenweb/houzz isn't what it used to be. I don't know what the motivation is but perhaps too much time watching American Idol with their abusive judges there to up the TV ratings?? Maybe not enough reading comprehension? Just here to sneer at so-called "stupid" questions?? Yes, this thread is a part of what my comments address but I frequent this site and I see a LOT of very uncalled for comments in many threads...and sadly, lots of the snark is coming from those designated as Pros.

To be clear, Mr. Corlett, I think led off with some incorrect information early on here but I didn't see anything he provided that I thought was snarky, unprofessional, or inconsiderate.....I saw him catching heat in another recent thread that was entirely uncalled for so I think he/you know what I'm commenting on. It's everywhere now....even here.