Adding utility sink to basement. Any code issues? Help? I

[Bomaifam]

I want to add a basic utility sink in my basement. The area where i want to add it is directly next to my 4" pvc main sewer pipe that leaves my basement out to my street. Would there be any problem with me just adding a tee to the 4" pvc that has an outlet that i can add a trap and run to the drain of the sink. I have attached pictures of the 4" pvc and the tee fitting im talking about. Any help would be greatly appreciated

 

[Twowaxhack]

That’s fine but you’ll need to vent it.

 

[Bomaifam]

That’s fine but you’ll need to vent it.

Thank you for your response. Are you talking about something like this? Is that so it dosen't pull air through the trap and let gasses out instead pulling air through a one way valve?

 

[Twowaxhack]

That might work but it might not. That will protect the trap from siphoning.....

BUT, the laundry sink being at the bottom of the main stack without any other atmospheric vents, water may be blown out of the trap under certain flow conditions. Positive pressure......

Blowing vs sucking. Toot vents protect against sucking.

 

[Bomaifam]

Gotcha. Would adding a second tee on the 4" main pipe above the one that will go to the sink with pipe looping the 2 together be an effective way to vent? I included a photo of it. If not what would be the best way? Thanks again

 

[Twowaxhack]

You would need to extend a vent above the roof or connect into another vent to meet typical plumbing codes.

Doing what you have drawn, and spacing the tees as far apart as possible would be better than nothing. The idea is to keep a constant flow of air. Under heavy load you may not be able to have that constant flow of air without a proper vent.

Try it and see. After you pipe it all in, run every fixture in the house at once except that sink.

I’m telling you it’s against code, I’m not saying it will not work and work flawlessly.

 

[MicEd69]

You would be OK with your first proposed installation if your stack ran straight up from your sink tie-in point and your sink was within 6 feet or 42" of the stack, depending on which plumbing "theory" you are under. But your main line runs horizontally under your floor joists for some distance, so as Twowaxhack indicated, the sink will need to be dry vented. You do not show the length of the horizontal main drain run between your vertical tie-in point and where the upper-level(s) vertical run drops into that horizontal line. Perhaps an easier way to vent this sink and maintain a code installation without having to install a new vent through the roof, would be to run a 1 1/4" vent pipe from the top of your sink drain line into your attic. If this is a single-story house, that may be relatively easy to do. All you need to find is an open space between a set of studs relatively close to the vent stack. If this isn't a single-story house, this approach could be exceeding difficult, however. After you are in the attic, all you need to do is tie this 1 1/4" vent into the existing vent stack. I've been able to do this twice and it was really easy in a single-story house; once for a new basement sink, and once for a new basement washing machine installation. Just note that any horizontal runs need to be sloped 1/4" per foot minimum but can be sloped steeper as this is strictly a vent, not a drain line.

 

[Twowaxhack]

You would be OK with your first proposed installation if your stack ran straight up from your sink tie-in point and your sink was within 6 feet or 42" of the stack, depending on which plumbing "theory" you are under.

No code in the United states would allow that piping configuration.

 

[MicEd69]

Oops, made another mistake. The "theory" I was using was using for that scenario was the wrong "theory".

 

[Bomaifam]

You would be OK with your first proposed installation if your stack ran straight up from your sink tie-in point and your sink was within 6 feet or 42" of the stack, depending on which plumbing "theory" you are under. But your main line runs horizontally under your floor joists for some distance, so as Twowaxhack indicated, the sink will need to be dry vented. You do not show the length of the horizontal main drain run between your vertical tie-in point and where the upper-level(s) vertical run drops into that horizontal line. Perhaps an easier way to vent this sink and maintain a code installation without having to install a new vent through the roof, would be to run a 1 1/4" vent pipe from the top of your sink drain line into your attic. If this is a single-story house, that may be relatively easy to do. All you need to find is an open space between a set of studs relatively close to the vent stack. If this isn't a single-story house, this approach could be exceeding difficult, however. After you are in the attic, all you need to do is tie this 1 1/4" vent into the existing vent stack. I've been able to do this twice and it was really easy in a single-story house; once for a new basement sink, and once for a new basement washing machine installation. Just note that any horizontal runs need to be sloped 1/4" per foot minimum but can be sloped steeper as this is strictly a vent, not a drain line.

Here are some photos of the main drain. It runs most of the length of my basement. This building is a 2 family so above the main floor is a second floor with anouther unit. There is a small attic above the second unit only a few feet tall so an attic you have to crawl through. It would be a serious mission running it from the basement though my unit to the second floor unit to the roof. Is there anyway to determine where the vent pipe is from the basement? I assume the vent has to go to the roof and not somewhere else on the exterior of the house? There's nothing in the basement that has a drain no sink, laundry, ect. Everything is on the first floor and the second floor has its own laundry ect. Would there even be access to a vent pipe in the basement or would it probably be up higher starting on the 1st floor? I don't mind not being up to code as long as it functions properly. Eventually i will move out of my unit and rent it out so it will need to be up to code for an occupancy permit but i dont mind just capping off and removing any plumbing i do before that. But i plan on putting the sink right next to the stack to make it easy and i have space there anyway. I attached a photo. I plan on putting the sink right where those sheets of playwood are.

 

[MicEd69]

The main vent is usually just a continuation of the main stack, but with your arrangement, you could have multiple vents depending on the layout of the 2-family unit. There is not an actual "vent pipe" that would be in the basement if there are no existing plumbing fixtures there. And the only way to tell the vent point(s) would be to look in the attic. And as you said, getting a pipe to a vent in the attic in your 2-family unit has a host of problems. All vents have to extend above the roof line and meet certain criteria. Theoretically, you could run a vent through the rim joist and up the side of the building to above the roof. But you would have to deal with the eaves and there are other vent criteria that you would have to follow. And that option would not be very appealing looking.

If you are going to do as Twowaxhack indicated and your revised sketch shows, use the 4"x4"x1 1/2" sanitary tee you showed for your drain. But for the "vent", use a 4"x4"x1 1/2" reducing wye pointed up and use 1 1/2" for the "vent" piping. The sink "vent" would come off the horizontal sink drain like this.

The "vent" pipe should continue up to a "loop vent".


The "vent" side of the loop vent will then 45 into the reducing wye. I would make the loop vent up to the floor joists. This will help provide additional air volume so that a maximum drainage flow will not pull the trap dry. It will also be advisable to run water in that sink at least monthly to assure there is always water in the trap.

 

[Twowaxhack]

Do not use a 4x4x1.5” tee. Use a 4x4x2.

A loop vent would be ineffective for positive pressure at the base of a main stack with only one connection to the main stack.
One connection point would get closed off by high flow, even more so if someone used 1.5” pipe. The bigger the pipe the better.

If you only install one tee in the stack, 4x4x2 just use a studor vent. It’ll work better than a loop on the fixture arm.

Use 2- 4x4x2 tees spaced as far apart as possible in the vertical. You could also add a studor vent if needed.

The objective is to stop positive pressure.

You can’t stop positive pressure if there’s only one connection to the main stack with a loop on the fixture arm.

 

[Twowaxhack]

Double post !

 

[Bomaifam]

Do not use a 4x4x1.5” tee. Use a 4x4x2.

A loop vent would be ineffective for positive pressure at the base of a main stack with only one connection to the main stack.
One connection point would get closed off by high flow, even more so if someone used 1.5” pipe. The bigger the pipe the better.

If you only install one tee in the stack, 4x4x2 just use a studor vent. It’ll work better than a loop on the fixture arm.

Use 2- 4x4x2 tees spaced as far apart as possible in the vertical. You could also add a studor vent if needed.

The objective is to stop positive pressure.

You can’t stop positive pressure if there’s only one connection to the main stack with a loop on the fixture arm.

Gotcha. I'll use 4x4x2. Would this be acceptable? Thanks again for your input

 

[Twowaxhack]

Put both tees in the main stack with the sweeps going down. The farther apart the better.

Use a combination fitting on the horizontal to go up for the vent. Be at least 4” from the trap, preferably more.

 

[MicEd69]

Do not use a 4x4x1.5” tee. Use a 4x4x2.

A loop vent would be ineffective for positive pressure at the base of a main stack with only one connection to the main stack.
One connection point would get closed off by high flow, even more so if someone used 1.5” pipe. The bigger the pipe the better.

If you only install one tee in the stack, 4x4x2 just use a studor vent. It’ll work better than a loop on the fixture arm.

Use 2- 4x4x2 tees spaced as far apart as possible in the vertical. You could also add a studor vent if needed.

The objective is to stop positive pressure.

You can’t stop positive pressure if there’s only one connection to the main stack with a loop on the fixture arm.

Reread my post please.

I indicated to use Bomaifam's second sketch that has two stack connections that you agreed that didn't meet code but might work. My clarification is that the lower connection to the stack should be a sanitary tee, but the upper connection to the stack should be a wye. The "loop vent" would start at the fixture drain arm meeting the 2 pipe diameters criteria shown in the sketch, go vertical as high as possible, then drop down into the wye installed higher up the stack. But I wouldn't install it as high as possible, but rather install it such that the dimension between the wye connection and the top of the "loop vent" is at least 3 feet. With a 4" stack, the theory would be that there would be sufficient air in that vertical run to adequately maintain trap integrity during most any reasonable plumbing condition in this 2-family unit.

I dislike AAVs with a passion and would avoid them an almost any cost. I don't believe one would be required here. But as you said, this is not per code, but I think this would work. And your 2" pipe suggestion would provide additional volume and would be better.

 

[Twowaxhack]

The two sanitary tees in the main stack with the vertical extension off the fixture arm would effectively make a loop of air.

This would prevent positive pressure being applied to the trap and most likely negative pressure as well.

The studor vent would take care of any negative pressure if it were present.

 

[MicEd69]

A sanitary tee on the bottom drain connection and a wye on the top would make a much better loop of air, and better protects against any possible buildup of solids at the "vent" connection.

 

[Twowaxhack]

A sanitary tee on the bottom drain connection and a wye on the top would make a much better loop of air, and better protects against any possible buildup of solids at the "vent" connection.

A better loop of air ? How many house drains have you cleaned ?

Tees will work fine.

You guys have a great night, this ones done for me.

 

[Bomaifam]

Thanks everyone for your help much appreciated