Plumbing Vent Question

[eng1886trk]

This is a question for the plumbers in the group. I am looking to add a basement bathroom with a sump pit. With how close the fixtures are to the pit and the fact that the pit is vented, do I need to vent near the lav? If so would an air admittance valve work under the sink to accomplish this?

Picture is a rough sketch of what I am thinking of doing. 4” for roughly 3 feet to pick up the toilet and washer drain and then an additional 7 feet of 2” to the lav.

Pit will be vented to the exterior.

Please let me know your thoughts so I do this correctly.

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[Cglaza]

This is a question for the plumbers in the group. I am looking to add a basement bathroom with a sump pit. With how close the fixtures are to the pit and the fact that the pit is vented, do I need to vent near the lav? If so would an air admittance valve work under the sink to accomplish this?

Picture is a rough sketch of what I am thinking of doing. 4” for roughly 3 feet to pick up the toilet and washer drain and then an additional 7 feet of 2” to the lav.

Pit will be vented to the exterior.

Please let me know your thoughts so I do this correctly.

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With the proximately of the pit to the toilet, when your pump cycles, you will likely experience cavitation in the toilet due to the violent nature of the pump action. Make sure that your vent out of your sump is as big as possible and as short as possible with as little turns as possible. No other vents will be necessary. Good luck with your project. I did the same thing and enjoyed the outcome very much.

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[North Idaho Wolfman]

I don't fully agree with Cglaza,
I think you need vents on the lav and on the toilet, new codes ever require a vent on the washing machine line.

I have just plumbed my house and have vents off of all three fixtures.

How hard would it be to incorporate a 1 1/2 (lav and washer) and 2" (toilet) vent line off of those drain lines vented back to the sump vent?
That would guarantee to air intrusion or dry trap issues.

 

[sagor]

I don't fully agree with Cglaza,
I think you need vents on the lav and on the toilet, new codes ever require a vent on the washing machine line.

I have just plumbed my house and have vents off of all three fixtures.

How hard would it be to incorporate a 1 1/2 (lav and washer) and 2" (toilet) vent line off of those drain lines vented back to the sump vent?
That would guarantee to air intrusion or dry trap issues.

I agree somewhat with Wolfman. However, if you vent the LAV, it "could" be considered a "wet vent" for the toilet, meaning that the LAV vent is used for the toilet since it is often not possible to use both at the same time. This LAV vent would also provide the pressure relief when the pump runs, to prevent cavitation as one described (suction/vacuum).
Safest is to vent all 3, and could probably be the same 2" vent pipe from the sump vent.
I'm not a plumber, but have gone through a couple "inspections" by those anal building inspectors. They always find something wrong at the end of the inspection, right after they ask "who did your plumbing". Nothing wrong before that question...

 

[Bulldog777]

You could plumb the tee's in for the vents, and if you need them... add them later.

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[Redlands]

I really think you need a vent on the lavatory. It’s at the end of the line and so will help all of the issues. Since the line is fairly short it maybe all you need. It can vent out or I believe it can circle back high up into into your exiting vent so as to prevent another roof penetration. They also make vents you can install under the lavatory sink that has a flapper valve in them. Not a huge fan but their real common. A vent for the commode is always a good idea and could be in that same vent loop if needed. No idea on the code for your area but its way better to have more vent than needed.

 

[johnjk]

When we build last year, I had them rough in for a basement bathroom so the pit is there along with the piping for toilet, shower and sink. There is a vent stack that runs up and out separate from the piping for the pit. This will be connected to the pit and the sink being the last in the line. Toilet and shower will be vented by the sump.

Looking at the attached image, the red horizontal line is the waste line to the septic. This will go down to the pit circled in green. The blue circle is the shower, the yellow is toilet and pink is for the lav. The purple arrow is the vent rough in for the basement bath and that will be run down to the pit and over to the lav.

In your case, connect your washer and lav in to the vent as well. Look online and google basement plumbing venting with sump pit.

Key is you do not want air trying to equalize coming back up the drain pipe. That will give you slow and noisy drains or worse case water on the floor.