Blackbeard

I'm coming in on the middle of the conversation here. Do you mean that a toilet needs a 3" vent?

I *would run 3" if I could I'm not cheap on materials, but no, Mike. 2" before VTR. We know there is far more than a simple statement saying this. I just say physics says no to 1 1/2". I have the math, I can post it later. Air pressure is the most important thing in venting. You must maintain the +/-1" in P traps for balance.

I say no also due to the cold weather in CO as it could block the vent in 24 hrs depending on temp. I say no as a bird could block that small vent for the Lav. I say no as I would not want to go back and tear out the walls if they have venting problems.

Its his buisness, he says it will save him money. Ok.

thats a lot of what ifs? so in a back to back you would need a six inch vent?

huh? My code still says one 3" in a dwelling.

Well OK. The picture you painted was that of a 3" pipe totally filled with water, and then pulling a perfect vaccum. The water gets all spread out, and in a stack, it adheres to the sides of the pipe. The way you were making it sound was that you'd need a 3" vent to replace the air so that the sink trap would be protected. No wonder I was wondering.

"jim donovan"

At the restaurant, they'll need a 12" vent! Wow!

I never meant it that way. Some don't know that fluids *swirl in a Hoz. line a short distance from initial start point. If in a stack over 3 floors or 30', fluids stops and equals gravity and a slug of fluid falls over the stopped slug and all slugs still have 7/24 of Air in its center, this is what makes for the air balance in the P traps +/- 1". 7/24 is a constant.

So, in a stack; I mean that a 7/24 of 3" is larger than 7/24 of 1 1/2 " So, there is less chance of self siphoning.

In a Hoz. line that goes into a T then a Stack, the fluid will not hit the opposite side of the inside Stack line. ( gravity conditions) Providing the Hoz. is equal or less then the Stack size. So, even here there is air. Its the volume of air to be concerned about for balance. Size matters.

Just like in, ' Bob's male enhancement ' commercials.

size does matter,but the reason Bob is smiling is that he has not read your last post. jp@yahoo

Hey, that s*it works. That's why I step on my dick.

The way these things are figured is to look at the charts in the applicable code book. They've assigned fixture units for various fixtures. You look at the load, calculate the appropriate developed length, and see which size pipe to run. By these figures, for example, if there's a full bath, you can vent a bathtub with 1.5", vent the toilet with 2", and even wet vent it with a lav. It works just fine. You tie these vents together and run them to the vent stack (or stack vent). Now if you want to run 3", it's OK. I guess you could run 4", but it won't work any better.

mike grooms if they are wall hung toilets (4 inch waste) you would need a 16 inch vent ,dbl wow but only one 3 inch vtr. i wonder who makes a 16 inch studor vent?

guess you want to ignore what you have seen yourself.

I suspect you'll find that air flows through PVC easier than liquids. So, the smaller vent line would work OK.

Warning: I am not a plumber!

Nor am I. I'm a Plummer.

"Stormin Mormon"

Gee, why not just draw a bullseye on your chest?

I think I'll surf over to alt.medicaldoctors and tell them which EEG machine I like best., or how I think an MRI should be done.

Now go back to one of your wives and repent.