sewer venting and toilets


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Old 07-28-18, 03:39 PM
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sewer venting and toilets

I had some generic questions regarding sewer venting and toilets. Based on reading, it is suggested that as a "rule of thumb" that a toilet must be located within 5'-6' of the sewer stack.

That being said, there has been discussion of remodeling a portion of the house (on main floor) , and adding a 1/2 or 3/4 bath. This location currently has plumbing (washer and dryer reside here). This location is roughly ~ 20' from the existing stack.

There has also been a utility sink location plumbed to this location (done by me), and it does have an issue draining slowly, which I am guessing is due to lack of venting, since I just added a tee to the washer drain (in the basement) to supply a drain for the utility sink.

Currently, near the washer drain connects to the main drain (in the basement), there is a section of pipe that is a square that is tied to the drain that I am guessing acts as a vent pipe for the washer drain.

My guess is that if I took out the square section of vent pipe, and tied that directly to the sewer stack that this would provide sufficient vent supply to add a toilet to this space?

Any advice is greatly appreciated.
 
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Old 07-29-18, 04:29 AM
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You've covered a lot of different things in your post. It's impossible to tell you what you can do without knowing how your house is plumbed. I suggest you read about the piping and venting required for a toilet.
 
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Old 07-29-18, 05:56 AM
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If you're adding a new bathroom, you're most likely going to need a new 2" vent out through the roof. It's usually not as bad as it seems, if you can find a closet or similar chase, you can go through the upper levels.

Even if you're close to the stack, if there are fixtures above that drain into the same stack, you can no longer use that stack as a vent (wet vents aren't allowed).

For just a laundry sink, you can often get away with an AAV (Studor vent), but I wouldn't recommend one for a bathroom group.

(And I don't know what you mean by a square vent)
 
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Old 07-29-18, 10:32 AM
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Thanks for the responses, everyone. I did read up on the studor AAV, and that looks like it would be the solution to the drainage issue for the laundry sink.

Here is a photo of the square piping that I had a question about. Is this some type of a vent?



https://drive.google.com/file/d/1Ekn...ew?usp=sharing


As for the existing plumbing, all of the plumbing resides on the main floor. There are not any fixtures that connect to the sewer vent any further above it.


Here is a picture of where the current stack resides



https://drive.google.com/file/d/1Yj0...ew?usp=sharing

The 4" pipe on the left is where the sewer stack currently goes up to the roof. The 4" pipe on the right is where the existing toilet resides. It's tough to tell in this picture, but all of the other drains tie in after the vent.

In short, would it be possible to tee off the existing vent stack and extend that vent so that a toilet could be added to another location?

Thanks.
 
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Old 07-29-18, 12:02 PM
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You can tie into an existing vent stack, but at 42" above the floor that the fixture is on. IOW, you can't go up and back down.

The PVC square is kind of amusing. It serves no purpose and looks like some jovial plumbers used some extra fittings to cover up an error. Perhaps installed on a Friday at the end of the day over a few beers.
 
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Old 07-30-18, 10:02 AM
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Gotcha, so everything is on the 1st floor.

You can drain into the main 3" drain, but you'll still need a 2" vent for your new bathroom. It's typically just vented up through the vanity, up to either the attic, or can tie over to the stack, but at least 42" above the floor as Steve mentioned. Since you're well over the 5' limit, plus you'll be using a vanity anyway, it all needs to be vented.

I would have never believed you if you described that "square" setup. No idea who came up with that idea!
 
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Old 07-31-18, 07:22 AM
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I would have never believed you if you described that "square" setup. No idea who came up with that idea!

Isn't there some sort of weird vent a person uses for a kitchen island that looks sorta like that?

No idea myself and this sure isn't an island.
 
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Old 07-31-18, 07:37 AM
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There are "square" vent loops. But, to be effective there needs to be two connections to the drain line. A vent loop with only one connection is nothing but a waste of pipe. My inspectors do not allow them though. Vents must go up and out the roof. They will make exception for a kitchen island and allow a air admittance valve (AAV) but do not allow them elsewhere. Laziness or not wanting to cut open a wall is not an excuse for not running a proper vent line up through the roof with my inspections.

If I understand your question correctly, yes you can tie into your existing 4" vent. It is most commonly done up in the attic to minimize the number of holes in the roof. Keep in mind that 2" minimum size is required for a toilet and horizontal runs are not permitted. They still need pitch for drainage just like a drain line.
 
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Old 08-01-18, 06:06 AM
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Thanks for all of the responses, everyone.

Based on the feedback that I have received, it sounds as though I cannot extend the sewer vent via the basement but it would rather have to be extended through the attic.

In this particular situation, where the potential bathroom would be added does not share attic space with the area that contains the existing sewer vent. With that, it sounds like the best option here would be to install a new 3" stack from scratch specifically for that area. Please let me know if I missed anything

Thanks for the advice.
 
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Old 08-01-18, 06:28 AM
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Since the new bath doesn't share attic space with the rest of the house you run a new vent up through the roof.
 
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Old 08-01-18, 09:46 AM
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Yup, sounds like you're on track. Note that a vent for a bathroom group only needs to be 2". No reason to run 3" up through the roof.
 
 

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