Drain vent

[mrordinary]

The plumber and I were trying to figure out how to vent a bathroom in the basement with an aav.

Option
1. Figure a way to go into 1st floor closet, then try to 45 degree into the attic crawlspace to the existing roof vent. It would be very difficult

2. Cut through the joists in the ceiling. The problem is that each joist is 7 3/8 and we need to drill out 2 9/16. That hole is slightly too big to drill out by code. (Not sure if it is allowed if the joist is a thicker joist from 1929.

3. He came up with an idea he could run a vent from under the slab, but the sink would need an aav.

There was 4 inch cast iron in the trench that now has 3 inch pvc.
At the top of the 3" sewer is the 2 inch vent for the shower and toilet.

See pic.

I then read about spill zones after he left.is this setup code?

 

[MicEd69]

You have not provided enough information to provide an answer. There has to be a toilet vent somewhere in the system, but the location of it isn't as important as the sink, shower, or tub vents. A layout with the location of the basement fixtures and the main stack is required.

A sewer vent must be vertical or no more than 45 degrees off vertical until you get 6" above the flood plain of the last fixture going into that vent line. And there are restrictions as to what can be "wet vented", which means any fixtures that would use that "vent line" as a drain. But once you get above the flood plain of a fixture with no other fixtures draining into it, you can run the vent line at a 1/4" per foot slope draining back to the sewer to which it is connected. That may make an actual vent line a little easier. I'm surprised that you said, "the plumber and I", as a plumber should know acceptable vent line routing per the codes.

 

[mrordinary]

The plumber threw out a few ways like going vertical to the roof and going through the joists but those were difficult or impossible.

He then said he had the underground idea. I now question it.

I did my best to sketch the diagram but it looks like a 2 year old drew it!

 

[MicEd69]

From your picture, I take it the wye with the two street ells is the vent in your drawing. That will vent the toilet, but not the shower. The shower vent must be vented in the trap arm before it connects to the horizontal main drain. As that is a proposed vent will obviously be below the floor level, it looks like you would have enough room to vent the shower through that same dry vent.

You can use a sanitary tee on its back for the shower vent saving some room, but with the reducing wye from the shower laying totally flat, that could cause a problem. I would have installed the shower reducing wye so that it entered the horizontal sewer line at an angle, 45-degrees would be great but not required, to keep any flow from the main line from backing up into that shower line. Then, a sanitary tee on its back would be totally acceptable when used as a vent.

Oh, the sink must also have its vent in the trap arm as well.

 

[mrordinary]

If you put the wye of the shower at a 45 degree, wouldn't that mean the shower could backup or clog since it has to travel upwards? Would a backflo preventer be what I need?

 

[MicEd69]

You are misunderstanding what I'm saying. The current 2" shower drain enters the main 3" line flat. Even though it is a 3"x2"x3" reducing wye, you still have a good potential of solids entering the shower drain line. Best practice is for drain lines to enter the horizontal mains from above, vertically if possible and at no less than a 45-degree angle from above. That means the shower drain line is not as deep as the main drain line.

No, you would NEVER run any drain so yhe flow has to go uphill, and you would NEVER us a backflow for your current layout.

 

[mrordinary]

That makes much more sense.

Would a backwater valve make sense then when the pipe exits the house?

 

[CT18]

In my area it is code that all basement fixtures are protected with a backwater valve

 

[MicEd69]

That makes much more sense.

Would a backwater valve make sense then when the pipe exits the house?

Like CT18 said, many codes require that. Most houses are grandfathered in unless/until you have major plumbing done like yours. I would check with your local authority. I am surprised that your plumber didn't recommend one as again, that is best practice today.

 

[Scrat]

Have you asked if a WET vent is code? I did a basement full bath before and it was ok to connect the vent to the main stack , so mu vent ran into the joists to the stack and tied into the stack with an inverted "Y" so no water or moisture would back flow into the vent ) where the Y turned down at the stack. Just an idea if its code... it was 20 years ago when I had this done.

 

[MicEd69]

Have you asked if a WET vent is code? I did a basement fukk bath before and it was ok to connect the vent to the main stack , so mu vent ran into the joists to the stack and tied into the stack with an inverted "Y" so no water or moisture would back flow into the vent ) where the Y turned down at the stack. Just an idea if its code... it was 20 years ago when I had this done.

Wet vents can be used, but not on a main stack.

 

[Scrat]

Wet vents can be used, but not on a main stack.

View attachment 39000

View attachment 39001

and your top photos show exactly that I explained, labeled as branch vent.... as I explained? .

 

[MicEd69]

and your top photos show exactly that I explained, labeled as branch vent.... as I explained? .

From your description, it sounded like you connected your basement "vent" to the soil stack with a wye like in my bottom picture. But if you did install the vent in the vent stack, which is the part of the main stack that has NO water or waste flow from any fixtures above it, and if you used a Sanitary Tee instead of an "inverted wye", then you actually installed a proper DRY vent.

A vent cannot be installed to a soil stack.

 

[Scrat]

From your description, it sounded like you connected your basement "vent" to the soil stack with a wye like in my bottom picture. But if you did install the vent in the vent stack, which is the part of the main stack that has NO water or waste flow from any fixtures above it, and if you used a Sanitary Tee instead of an "inverted wye", then you actually installed a proper DRY vent.

A vent cannot be installed to a soil stack.

View attachment 39009

Correct, a sanitary T ( not a Y or wye ) I couldnt think of the name, as I had a plumber do this so it was code when it was done. I know some codes in one place wont pass in other places, crazy but thats how they make their money and headaches

 

[mrordinary]

Like CT18 said, many codes require that. Most houses are grandfathered in unless/until you have major plumbing done like yours. I would check with your local authority. I am surprised that your plumber didn't recommend one as again, that is best practice today.

Like CT18 said, many codes require that. Most houses are grandfathered in unless/until you have major plumbing done like yours. I would check with your local authority. I am surprised that your plumber didn't recommend one as again, that is best practice today.

When the main sewer line was done 2 years ago it wasnt added. This plumber said that adding it would be useless because technically it should be added after both lines intersect. Unfortunately both lines intersect as the pvc goes under the foundation.

The only option now is to put it as the intersect to one drain inside.

Like CT18 said, many codes require that. Most houses are grandfathered in unless/until you have major plumbing done like yours. I would check with your local authority. I am surprised that your plumber didn't recommend one as again, that is best practice today.

 

[mrordinary]

Ok so I am confused. Since the vent is an inverted wye that goes into the main sewer line it is not allowed?

I get that the shower is not vented. So does that need a sanitary T and then a horizontal run as shown by the other run?

 

[mrordinary]

I think it wasnt recommended because he said that usually this is added right before it exits the house. Unfortunately it it impossible to do this because two sewer lines attach, one from above and one under. There is no way to put a backflow preventer unless it is on each line that ties together and he seemed to indicate this is not code.

 

[MicEd69]

Ok so I am confused. Since the vent is an inverted wye that goes into the main sewer line it is not allowed?

I get that the shower is not vented. So does that need a sanitary T and then a horizontal run as shown by the other run?

There are multiple discussions going on in this chain and now I'm confused as well.

Your statement of, "the vent is an inverted wye that goes into the main sewer line", is confusing. Are you meaning to say that the vent is a wye laying on its back at a 45-degree angle? Something being "inverted" refers to something in the vertical. If that is what you are referring to, then that IS allowed, and that line vents the toilet. However, it should really maintain its 45-degree or steeper angle until it is 6" above the bowl height of the toilet before going horizontal. You need to put a cleanout in that vent line soon after it rises above the floor.

To vent the shower, go back to my earlier post. It can be a Sanitary tee on its back vertically, or no more than 45 degrees off vertical, until it gets 6" above the shower base before it goes horizontal.

While you have provided a lot of pictures, it is hard to tell what is what, and without knowing where walls are or the elevations of the drains and the floor, it's pretty hard to provide good advise.

 

[mrordinary]

There are multiple discussions going on in this chain and now I'm confused as well.

Your statement of, "the vent is an inverted wye that goes into the main sewer line", is confusing. Are you meaning to say that the vent is a wye laying on its back at a 45-degree angle? Something being "inverted" refers to something in the vertical. If that is what you are referring to, then that IS allowed, and that line vents the toilet. However, it should really maintain its 45-degree or steeper angle until it is 6" above the bowl height of the toilet before going horizontal. You need to put a cleanout in that vent line soon after it rises above the floor.

To vent the shower, go back to my earlier post. It can be a Sanitary tee on its back vertically, or no more than 45 degrees off vertical, until it gets 6" above the shower base before it goes horizontal.

While you have provided a lot of pictures, it is hard to tell what is what, and without knowing where walls are or the elevations of the drains and the floor, it's pretty hard to provide good advise.

I will try to give better pics with walls and elevations this weekend

 

[mrordinary]

I will try to give better pics with walls and elevations this weekend

I attached how the line drains to tge street.

I also put wood pieces across to represent the level of the floor.

1. I want to understand my venting system. Would this be a wet or dry vent? I think it is dry since no waste goes through the wye that attaches to the 3 inch waste.

2. I agree that the shower should go higher up and attach higher like the vent.

3. As you can see there are 2 lines that intersect downstream. No backwater valve was installed 2 years ago when another plumber did the job. This plumber said that it is pointless to put a backwater valve on the lower line because sewage can backfill into the top line. This plumber said that the backwater valve should have been installed at the intersection. We can't do that now because that intersection is under the foundation wall.