Dry vent vs. wet vent

[msteger]

I have long heard the terms 'dry vent' and 'wet vent' pertaining to venting systems for plumbing. It appears that a wet vent is simply a dry vent that also has drain water running in it (such as the typical PVC DWV system in the home above the highest drain connection (sink, tub, etc.) in the home). How does one tell the different b/w the two?

I run across this often with ejector/effluent pumps in basements with dual PVC vertical drain pipes both connecting into the main sewer line (one is a drain and one is a vent). Maybe I just need a good summary of these two terms.

[ghentjr]

I have long heard the terms 'dry vent' and 'wet vent' pertaining to venting systems for plumbing. It appears that a wet vent is simply a dry vent that also has drain water running in it (such as the typical PVC DWV system in the home above the highest drain connection (sink, tub, etc.) in the home). How does one tell the different b/w the two?

I run across this often with ejector/effluent pumps in basements with dual PVC vertical drain pipes both connecting into the main sewer line (one is a drain and one is a vent). Maybe I just need a good summary of these two terms.

Plumbing Vents: types of vents, wet vents, dry vents, vent ...

[Marc]

Plumbing isn't my forte but this is from 'National Plumbing Codes Handbook' by Dodge Woodson:

Wet vents are pipes that serve as a vent for one fixture and a drain for another.

Marc

[Scottpat]

If you have (and you really should) a Code Check Complete or Code Check Plumbing, you will find some good diagrams of "wet vents" and proper uses.

[mgbinspect]

Plumbing isn't my forte but this is from 'National Plumbing Codes Handbook' by Dodge Woodson:

Wet vents are pipes that serve as a vent for one fixture and a drain for another.

Marc

That clears it up nicely. Thanks Marc!

[Bain]

I typically find these when someone's added a bathroom after-the-fact on an upper level. They don't want to install a new drain line through closets or whatever, so they just tap into the vent stack. The reason it's not allowed, clearly, is to prevent the vent from becoming clogged and to prevent the whooshing water and solids from screwing with traps in the house.

Those injection pumps should have separate connections to a drain and a vent stack. No way should both be connected to just a waste line. If you have a photo of a set-up you're concerned about, it would be helpful.

[msteger]

Thanks guys.. I don't have a specific example or photo, but just something I run across from time to time. Marc's definition is essentially what I have understood the term to mean: "Wet vents are pipes that serve as a vent for one fixture and a drain for another." This makes sense for a single story home... but for most 2 or 3 story homes, aren't just about all of the vents considered wet vents? A vent for the 1st level is often the drain for the 2nd level...eh?

I do have the Code Check Complete book. I assume you are referring to Figs. 35 ~ 39.

[Marc]

If I'm not mistaken, the plumbing codes in your part of the country (UPC?) make abundant use of wet venting techniques, more so than the South or West. They're not as common where I'm at. My own house has none.

Marc

[ghentjr]

I have long heard the terms 'dry vent' and 'wet vent' pertaining to venting systems for plumbing. It appears that a wet vent is simply a dry vent that also has drain water running in it (such as the typical PVC DWV system in the home above the highest drain connection (sink, tub, etc.) in the home). How does one tell the different b/w the two?

I run across this often with ejector/effluent pumps in basements with dual PVC vertical drain pipes both connecting into the main sewer line (one is a drain and one is a vent). Maybe I just need a good summary of these two terms.

Just google "plumbing wet vent" and you will have all the info you need.

[jackercracker]

A more inclusive definition comes from the 2010 California Plumbing Code:

A wet vent is a vent that also serves as a drain.

[Erby]

The typical sewage ejector pump in the basement around here has the actual drains INTO the sump under the slab, then a vent pipe to the venting system and a drain pipe to the drain system, both coming out the lid of the sump. Neither of the pipes allows sewage to flow INTO the sump.

[Charlie R]

What Erby said, two lines out of the top, one is for the flow out (with a check-valve) and the other is a vent that should always be a dry vent I would think. Flow in is under the slab.

[plummen]

Id say you guys covered it pretty well [^]

[Marc]

Id say you guys covered it pretty well [^]

'You guys'?

Marc

[plummen]

Im giving everybody credit today

[Layla]

Great timing guys!

I have been thinking about this for a few weeks now I am working on a basement refinishing project as I try to surrvive as I continue to aprentice with a local home inspector.

In the picture below you can see the 4" abs waste pipe, the home owners want to add a wet bar in the basement. To make this work I think I will need to add a sewer ejector pump. My question is can I tie in both the vent pipe and the waste pipe from the ejector pump into the 4" pipe shown in the picture? The cast Iron pipe thru the foundation is about 30" from the basement floor to the center of the pipe. If I put the vent pipe above the waste pipe will that work?

Click to Enlarge

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[kurt]

Nope. Ejector has to go to a drainage/waste pipe, vent to a vent pipe.

Wet vents came into being by being unable or uninterested to find and connect to a dry vent. More or less.

[Dank_Solo]

A dry vent has to be installed vertically from the trunk line because if waste ever backed up into a horizontal section of dedicated vent pipe that you couldn't run water through it would dry up and plug the vent. A "wet" section of vent can be horizontal because it can be rinsed/accessed (other than the roof!) Wet vent systems and dry vent systems have different applications. For example, we try to pipe all of our bathrooms in a way that the lavatory's stack vent is close enough to serve the tub and water closet. We can't all the time though (mostly in super huge master bathrooms) so sometimes we have to add a dry vent to serve the fixture that is too far away (almost always a shower or garden tub or both). This leaves a vertical section of vent pipe only accessible through the roof. Hopefully all of this information is still technically correct. Just thought i'd add a little practical info on how/when they are used in a home. Commercial buildings use almost exclusively dry vents, but those systems are engineered, residential plumbers have to figure the drain layout for themselves, as they are only given a floorplan, not a plumbing diagram to follow as close as possible. Greetings from Augusta, GA. Go Dawgs!

Edited September 10, 2021 by Dank_Solo
Im southern! Lol

[Marc]

I never really understood the difference between them two until now. You can explain all you want but until I get the 'why', It doesn't stick.

Good post. Who are you? Haven't seen you around here before.

Edited September 10, 2021 by Marc

[BADAIR]

wet dry vents.pdf