Bathroom trap sizes and fitting selection...

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hhcibtpaun

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Hey Folks,

Getting ready to start running the PVC for my bathroom drains. It is basically a tub, lavatory and toilet. My plan is to try to keep the piping for the lavatory and the tub in the same "joist bay". In order to accomplish this I may need to cheat the pipe that I drain the lavatory trap into toward the front on the vanity. May look odd, but it will save me from carving up the joists. I assume that is OK?

So, for the tub I know the drain is typically 1 1/2", is there any benefit to having a 2" trap and 2" piping after the trap? The plan is to have a glued p-trap and I will not have access to it once I close up the ceiling. If at some point in time it begins to leak, I will just cut a hole in my kitchen ceiling to do the repair....then probably stick a vented access panel. Is it OK to "bury the trap"?

For the vanity sink, should I dump the trap into a 1 1/2" or 2" pipe?

Since I plan to keep he drains for both the tub and the lavatory in the same bay, I had plans to join them with a wye. That will then run over to a 3" sanitary Tee with a 2"side inlet. I figure even if I used 1 1/2" pipes for both the lavatory in tub, they should be joined with a WYE, so I only need to run one pipe through the joist to get to the sanitary tee, which is where the toilet is....

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So, is there a benefit to having the larger pipe for the lavatory and tub (if I can fit it), or do I just keep it at 1 1/2" and join it to the WYE with a 2" outlet. The piping from the tub and lavatory is probably 2 or 3 ft max...

TIA...Mike
 

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John Gayewski

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There is no benifit to having a lav drain that's 2". The tub drain being 2"would be nice if anyone ever changed to a shower. How are you planning to vent these fixtures?
 

Jeff H Young

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I run 2 inch waste to both lavs and tubs with 1 1/2" vent and trap arms occasionally a very large tub in the master bath I'll go 2 inch trap. Its just the way I learned and I have never changed . My code requires 2 inch to the tub but trap and arm can be 1 1/2", Sometimes in unusual cases I'll run 1 1/2 to lavs like when there are structural issues.
Its normal to not have access to solid glue ptraps and glued waste and overflows on the tub.
Anyway I recommend 2 inch but you don't need to run that either tubs or lavs

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hhcibtpaun

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The tub drain being 2"would be nice if anyone ever changed to a shower. How are you planning to vent these fixtures?
Thanks John and Jeff.

I figured the bigger traps and pipes would be easier to snake or something. So, it sounds like either way I am safe. As for the venting that is a whole other mess. Right now I think the whole house is vented through the waste stack (I think I have my terms correct).

I ripped out a 3" CI stack that dumped into a 4" CI waste in the basement. I will be replacing that with PVC. House was built in the mid 1940's. I am assuming everything drained fine. I never lived in the house before I ripped everything out.

So, the upstairs has one bathroom with toilet, lav and tub, main floor had sink and dishwasher, basement has washer and utility sink.

When I was tearing everything out I saw no explicit vents on anything. I had a plumber out to look at replacing the waste stack and while I was talking to him I asked about the venting and he was like if it aint broke, dont fix it.

I think the bathroom could vent through the stack. Not sure how I could wind a vent from the basement or kitchen. My general plan was to get all the drains in and plumb everything with PEX. Once that is done I would turn everything on to see if I had any gurgling or drainage issues, before closing up the walls. Worst case I would need to figure out a vent or maybe do the AAV thing??

My gut tells me that if there were issues with the venting, they would have popped up over the last 75 years....

Thanks....Mike
 

John Gayewski

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I did a remod for a couple who has already done their bathroom they just wanted a kitchen sink and washer dryer. When I asked them if I could vent through the roof they looked at me like I was crazy. I had to tell them to Google it because they couldn't wrap their heads around why you'd need a vent. I asked them to stick their heads jn the existing kitchen sink and smell. They had never noticed their trap was siphoning. I noticed the smell right away.

If i were you I'd just properly vent your piping.
 

hhcibtpaun

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If i were you I'd just properly vent your piping.
Let me see if I can figure something out. Are the bathroom fixtures ok without an independent vent (and just using the stack - which goes through the roof)? I may have to try and draw a picture.

Thanks...Mike
 

Terry

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I was helping cook a meal at a friends home, and noticed it smelled bad in the kitchen near the sink. It hadn't been plumbed right, what a God Awful smell coming from the sink. I wound up redoing the plumbing to the sink, opening up the wall for it.
She had been hiring handymen, and there were so many issues with plumbing it was ridiculous. Almost everything needed something done to make it right.
 

John Gayewski

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I was helping cook a meal at a friends home, and noticed it smelled bad in the kitchen near the sink. It hadn't been plumbed right, what a God Awful smell coming from the sink. I wound up redoing the plumbing to the sink, opening up the wall for it.
She had been hiring handymen, and there were so many issues with plumbing it was ridiculous. Almost everything needed something done to make it right.
I sometimes wonder if those people got sick occasionally due to this trap siphonage. A doctor once told me that plumbers save more lives than any doctor could. Probably less so than in the past when modern plumbing was first developing.
 

John Gayewski

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Let me see if I can figure something out. Are the bathroom fixtures ok without an independent vent (and just using the stack - which goes through the roof)? I may have to try and draw a picture.

Thanks...Mike
Every trap needs a vent, every fixture with a drain has a trap. They can sometimes be combined or share, but that requires piping layout to be correct.
 

Terry

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I saw this on a Yelp review. They were complaining about price, but what I saw was a job done horribly wrong.
I have no idea what they were thinking.

ally-plumbing-washer.jpg
 

Jeff H Young

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Just about anything will work OK some of the time. But traps siphoning out is something serious , kinda like a gas leak in your home most of the time no one gets hurt but we don't want it ever happening 1 in 100 or even 10,000 isn't good enough.
Gas gets into sewer it can go in the house if trap isn't sealed and go boom
 

hhcibtpaun

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OK, I am going to try to figure out how to incorporate some vents.

I have a few questions to help me begin thinking.

1. The waste stack is 3" and goes through the roof to vent. I am hoping that I do not have to add anything else out through the roof. I have a slate roof and I could just see that as being a pain. So, can a 3" vent support Bathroom (lav, toilet, tub/shower), Kitchen (sink) and basement (laundry sink and washer).
2. If I am pushing the limit, maybe I don't have a dedicated drain for the washer? I guess I could just send the discharge hose into the laundry sink?
3. Can I use 1 1/2 pvc for all of these vents?
4. I am thinking one vent would be for the laundry sink and washer. Maybe I run that parallel to the waste stack, then connect into the vent above the bathroom (using 1 1/2" pvc).
5. The kitchen vent I assume I could use 1 1/2" for the sink. Initially I was hoping I could start the vent above the drain then loop in into the basement to pick up the other vent, but I think everything needs to move up.
6. In the bathroom, the tub is probably 6' - 8' of piping before it hits the waste stack. The sink is about 5' - 8'...I would have to layout a general look to get exact dimensions...in the worst case or 8' for each could these survive without a vent?

Any help is appreciated.

Thanks...Mike
 

John Gayewski

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3 inch will vent everything. 1.5"will work for venting as I think you follow ipc in Pennsylvania and it's definitely better than nothing. I think you should make a drawing of the bathroom so you can get some piping ideas as it sounds like your not up on it.
 

hhcibtpaun

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Thanks John. Yes I plan to sketch something up. Have to see if I can find some SW to do it, or maybe just old school pen and paper,
 

Jeff H Young

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OK, I am going to try to figure out how to incorporate some vents.

I have a few questions to help me begin thinking.

1. The waste stack is 3" and goes through the roof to vent. I am hoping that I do not have to add anything else out through the roof. I have a slate roof and I could just see that as being a pain. So, can a 3" vent support Bathroom (lav, toilet, tub/shower), Kitchen (sink) and basement (laundry sink and washer).
2. If I am pushing the limit, maybe I don't have a dedicated drain for the washer? I guess I could just send the discharge hose into the laundry sink?
3. Can I use 1 1/2 pvc for all of these vents?
4. I am thinking one vent would be for the laundry sink and washer. Maybe I run that parallel to the waste stack, then connect into the vent above the bathroom (using 1 1/2" pvc).
5. The kitchen vent I assume I could use 1 1/2" for the sink. Initially I was hoping I could start the vent above the drain then loop in into the basement to pick up the other vent, but I think everything needs to move up.
6. In the bathroom, the tub is probably 6' - 8' of piping before it hits the waste stack. The sink is about 5' - 8'...I would have to layout a general look to get exact dimensions...in the worst case or 8' for each could these survive without a vent?

Any help is appreciated.

Thanks...Mike
1 yes 2 yes dump in laundry sink if you wish 3 you have a 3 inch vent so everything wont be on 1-1/2". 4 yes 5 I would never run a kitchen sink on 1-1/2 but you probably can in your code mine doesn't allow it plus I think its inferior (just opinion) 6 8 foot is too long for a 1-1/2 " trap arm 2 inch will make it. the lav ? are you talking about a trap arm or waste line to Lav? if its the drain then you need a vent or AAV at the lav
 

hhcibtpaun

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OK Folks,

I have been away a few weeks and have been coming up with some options, but that has led me to a few more questions. I am hoping to be able to post some pictures of my final plan, after some feedback here :).

So, after thinking about my options I have three possibilities. My township uses the 2009 IPC code - International Plumbing Code, 2009 Edition

1. For my bathroom I have a lavatory and a tub/shower that I was planning to run a 2" drain on. It will be more than 5 feet, but less than 8' to get over to the drain stack (3"). Would this be plausible. From the IPC table it looks like I get 8 feet. So if I try to get closer to 5' than 8', am I golden? Could I drain the 2" drains to a 3" pipe for a short distance before the waste stack to just increase some volume? I know there is siphoning concerns, but is that minimized on fixtures that are used daily (bathroom) versus things that may see sporadic use (basement sink)?

2. If 8' is pushing it, is AAV an option?

I will ty to sketch this up tonight. Just wanted to throw this out for now.

Also, in the basement, if I drained my washer and laundry sink into the main vertical stack (3"), could that act as a wet vent (I think I have the terminology correct), or would I need explicit venting?

TIA...Mike
 

Reach4

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1. You will vent the lav. When you join the lav drainage with the shower drainage, that will wet vent the shower.

2. AAV is an option for venting, for the lav and for most other venting.

You still want to post a sketch of your plan.
 

wwhitney

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I did not review the thread.

1) if the 2" drain is going to carry both the tub/shower and the lavatory, then the lavatory will need a dry vent (since it's trap is above the tub trap, and vents are required at an elevation of within one pipe diameter of the trap). Then once the lavatory is dry vented, the tub will be wet vented by the lavatory. The tub trap arm (which again can only fall one pipe diameter) runs from the tub trap to the connection of tub and lavatory drains. The 3" stack will not be involved in venting.

But if the 2" drain is just for the tub, and you use a 2" tub trap, then your tub trap arm can be 8' long with up to 2" of fall. That 8' of length requires a perfect slope of the minimum 1/4" per foot. If that gets your tub trap arm to the stack, then depending on what if anything is draining into the stack above the tub connection, the stack can vent the tub. I.e a lavatory or a shower on the same level can drain into the stack above the tub connection, and the tub would be wet vented by the stack; any fixture from a higher story, or any WC connected above the tub, would prevent the stack from being used to vent the tub.

2) Under the IPC, an AAV is an option. It would need to be 4" above the tub trap arm, and accessible and ventilated. That can work in a joist bay, although it would be some trouble.

3) In the basement, if the 3" stack has any fixtures draining from a story above, it can not act to vent the washer and laundry sink. You would need other venting. AAVs are an option.

Cheers, Wayne
 

hhcibtpaun

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Thanks for the replies folks. I am going to spend the day tomorrow trying to get everything straight in my mind, so hopefully I will have pics with sketches on them. I did have one other question. My tub drain is right next to a joist (actually a double joist). Is it possible to just drain the tub, and have a second drain on the overflow. If I was able to do it this way I could run the drains in the joist bays, without notching the tops on the joists.....(this may require a picture).

Thanks...Mike
 

Reach4

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Thanks for the replies folks. I am going to spend the day tomorrow trying to get everything straight in my mind, so hopefully I will have pics with sketches on them. I did have one other question. My tub drain is right next to a joist (actually a double joist). Is it possible to just drain the tub, and have a second drain on the overflow. If I was able to do it this way I could run the drains in the joist bays, without notching the tops on the joists.....(this may require a picture).

Thanks...Mike
If the overflow had its own drain line, that would need a trap. And there would be concern about keeping that trap filled.
 
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