New guy here...

Plumbing Forums

Help Support Plumbing Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

tommyboy

Wyotech Plumbing Student
Joined
Oct 25, 2010
Messages
10
Reaction score
0
Location
San Diego, Ca
Hey new guy here, going to a trade mill school known as Wyotech in socal. We are entering venting section. What are the differences between wet vents and flat venting? Im still kinda confused, and when are they used?
 
A wet vent is a pipe that is used as both a vent for other fixture(s) and a drain for another fixture. The wet vent has to be oversized so that it can serve as both a vent and a drain at the same time. The most common use of a wet vent that I see is to vent a bathroom group, which usually consists of a water closet, shower/ tub, and lavatory basin, through the lavatory vent.

A vent cannot be dry and flat unless it is at least 6" above the rim of the fixture that it is venting. Dry means that there is not a fixture that drains through it, and flat means that the pipe is less than 45 degrees from level. The reason for this is that if the drain clogs up, and solid material gets into the vent, the solid material will likely stay in the vent pipe once the drain is cleared, and will continue to clog the vent. A wet vent "fixes" this by washing the drain water from the fixture through the vent pipe.

I am not too sure that I explained this very well, so if it is still clear as mud to you, post back.
 
Your saying that dry is just each fixture has its OWN vent? But flat, im still kinda confused. We did a flat one and couldnt finish it up. Im still kinda confused on 45 degrees from level?
 
We did a WC and a Bathtub and combined them together. The three inch was teed into a Wye and 2inches went horizontal at least 3 feet before going verticle. Is this what they mean?
 
A dry vent is a vent pipe that is ONLY a vent, and does not receive drainage water from a fixture.

A flat vent is a vent that runs horizontal instead of vertical. The "break point" for a pipe being horizontal or vertical according to code is 45 degrees from level. If the pipe is 44.999 degrees from level, than it is still considered flat. 45 degrees or more from level, and it is considered vertical.

We did a WC and a Bathtub and combined them together. The three inch was teed into a Wye and 2inches went horizontal at least 3 feet before going verticle. Is this what they mean?
The section of 2" pipe that went horizontal is PROBABLY a flat vent. I can't know this for sure, as I didn't see the piping arrangement. This flat vent pipe needs to be washed through by another fixture unless it is 6" above the rim of the fixture that it is venting.
 
A dry vent is a vent pipe that is ONLY a vent, and does not receive drainage water from a fixture.

A flat vent is a vent that runs horizontal instead of vertical. The "break point" for a pipe being horizontal or vertical according to code is 45 degrees from level. If the pipe is 44.999 degrees from level, than it is still considered flat. 45 degrees or more from level, and it is considered vertical.


The section of 2" pipe that went horizontal is PROBABLY a flat vent. I can't know this for sure, as I didn't see the piping arrangement. This flat vent pipe needs to be washed through by another fixture unless it is 6" above the rim of the fixture that it is venting.
Ok, im starting to see the picture. How about Island vents? I know what they are used for, but how do they work if they dont actually introduce into the atmosphere.
 
Doesn't an island vent contain a one way check valve to allow air to allow flow of water but prohibits gasses from escaping, and is set high within a cabinet so you don't have to deal with an ugly protruding vent pipe?
 
An AAV (air admittance valve) is the common way of venting island fixtures these days, and is basically a check valve on the vent pipe. However, there were methods used in the past that, IIRC, used an oversized drain pipe and basically a loop in the piping under the cabinet. The only time I saw this used was in the first 6 months or so my career, so the details are kind of hazy.
 
They just had a segment on last week's "Ask this Old House" and showed the contraption Phish is referring to, but has now been eliminated with just a highly placed check valve.
 
Wow. I guess I do have an lazy instructer, he made the whole class build this type of vent in our little teams. Talk about just giving us something to do... It took most of the day whilst he sat back. Not once did he meniton, "Oh by the way class, they dont make this style of vent, they stopped doing this years ago, now they use a check valve".
 
But I guess its still good learning and visually recognizing it when we see it in older houses, we can suggest an easier method to make more $$$
 
Your instructor is correct. Could you imagine a math instructor providing a calculator and saying, "It's not necessary to know how to multiply, because we have these new gizmo's!"
 
Picture of what you are talking about from google images.

I thought loop vents like this were still required by code.
But then again I don't do a lot of new install like that.
The last one I did was several years ago.

Island-loop_vent.jpg
 
Ok, im starting to see the picture. How about Island vents? I know what they are used for, but how do they work if they dont actually introduce into the atmosphere.

AAV's do not let air OUT. They admit air IN to prevent water in p-trap from getting sucked/siphoned out while draining.
 
Yeah, my instucter said they are common, he just installed one a month ago. But he said using the Power Flow check valve is NOT code.
 
I'm almost sure you're instructor is right.
I see you've up dated your profile and you live in San Diego.
Other municipalities may allow them.
They're always changing the code and code inforcement is weak.
Unless a permit is pulled a lot of work does not get inspected.

Good luck with school.
 
I'm almost sure you're instructor is right.
I see you've up dated your profile and you live in San Diego.
Other municipalities may allow them.
They're always changing the code and code inforcement is weak.
Unless a permit is pulled a lot of work does not get inspected.

Good luck with school.
Yeah, thanks for chiming in. I live in San Diego and I have to commute to Long Beach Ca on the weekends for plumbing school. I guess you know their are only two schools in SD that offers them. City is a two year wait and a assessment test that was built for kids right out of High School when it comes to Algebra.. The other one you have to be a working for a plumbing company already and its refresher courses.
 

Latest posts

Back
Top