Attic Bathroom Plumbing

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desithebuilder

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I am adding a bathroom to the attic and have been working with the plans to get the plumbing done. Below I have attached a sketch showing the fixtures. The existing main stack of the 2 floors below is right below the toilet, but I can not add a 3" main stack there as there is no room. I have to open the floor right next to the chimney enclosure and box it out, so the 3" main stack will be almost 6ft away from the toilet. The toilet will be vented with a wye combo going back and connecting with the shower vent pipe. The shower will connect with the horizontal 3" pipe with a combo wye. A combo wye will be used to went the shower. I am not sure if the shower vent pipe can run horizontally for 3-4 ft before the vertical run. The lavatory will connect to the 3" pipe with a 2" x 3" x 3" combo wye with a 2x3 reducer. The 3" horizontal stack will connect to the vertical main stack with a 3x3x2 SanTee, with a vent pipe running vertical, then horizontal to the right and then diving down due to roof slope and connecting with all other vent pipes to the existing vent going thru the roof. The joist run horizontally to the plans.
Can anyone see anything wrong with this layout? Any suggestion on how to make it better?



attic bathroom plumbing.JPG
 

Jeff H Young

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There is a lot wrong actualy. if you can bring the 2 inch to the shower to the wall on the right of shower pan put a combi on its back to vent then a long sweep on the trap arm for p trap that will be a vent for toilet as well the vent for toilet you have wont be needed and is prohibited.
BTW isnt that a waste of space having a tiny shower . i guess the scale is off but how do you squezze in next to the toilet for towles or whatever , looks like toilet can move over a bit toward the lav
 

desithebuilder

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There is a lot wrong actualy. if you can bring the 2 inch to the shower to the wall on the right of shower pan put a combi on its back to vent then a long sweep on the trap arm for p trap that will be a vent for toilet as well the vent for toilet you have wont be needed and is prohibited.
BTW isnt that a waste of space having a tiny shower . i guess the scale is off but how do you squezze in next to the toilet for towles or whatever , looks like toilet can move over a bit toward the lav
I have updated the plans a bit after looking at the joist configuration. I have eliminated the toilet vent. the shower pan is 40" x 48", probably the sketch is deceiving. My concern is regarding the 2" drain going thru the 2x7" joists. Distance from CL of shower drain to 3" main( 3x3x2 combo in orange) is 5'-4" (5 joists spaced at 16") and I can drop it only 1". Will this be an issue to drain the shower? Would you recommend downsizing to a 1 1/2" drain instead of a 2"? Also, not sure how much can the max drop be from p-trap to the main stack. I plan on scabbing the joists with a 3 ft long 2x7 and I will drill a 2 1/2" hole for the 2" pipe.
Any input is much appreciated.
1676682454043.png
 

Jeff H Young

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Its very blurry to read that drawing. what happens to the 2 inch line going to the shower is that a flat 2 inch combination wye 1/8thbend ? thats a dry vent ? your maximum fall comes in to play from the p trap to that flat combi but the problem might be if that pink line if its below flood level
 

desithebuilder

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I am adding a bathroom to the attic and have been working with the plans to get the plumbing done. Below I have attached a sketch showing the fixtures. The existing main stack of the 2 floors below is right below the toilet, but I can not add a 3" main stack there as there is no room. I have to open the floor right next to the chimney enclosure and box it out, so the 3" main stack will be almost 6ft away from the toilet. The toilet will be vented with a wye combo going back and connecting with the shower vent pipe. The shower will connect with the horizontal 3" pipe with a combo wye. A combo wye will be used to went the shower. I am not sure if the shower vent pipe can run horizontally for 3-4 ft before the vertical run. The lavatory will connect to the 3" pipe with a 2" x 3" x 3" combo wye with a 2x3 reducer. The 3" horizontal stack will connect to the vertical main stack with a 3x3x2 SanTee, with a vent pipe running vertical, then horizontal to the right and then diving down due to roof slope and connecting with all other vent pipes to the existing vent going thru the roof. The joist run horizontally to the plans.
Can anyone see anything wrong with this layout? Any suggestion on how to make it better?



View attachment 90114

Its very blurry to read that drawing. what happens to the 2 inch line going to the shower is that a flat 2 inch combination wye 1/8thbend ? thats a dry vent ? your maximum fall comes in to play from the p trap to that flat combi but the problem might be if that pink line if its below flood level
Document1.pdf1202.jpg

Jeff,
all the blu lines represent a 2" pipe which will have a 1/4" slope for the trap arm. from the wye combo to the 3" pvc drain (orange line) it will have a 3/16" slope for 5'-4" distance.7, then the slope becomes again 1/4" for the 3" drain ( in orange) that connects the toilet with the main stack on the left. The magenta lines represents the vent lines. the wye combo will be rotated up with 45 degree until it goes to the wall on the right, then it goes up with a 90 bend. my concern is the slope of the shower drain from the wye combi to the 3" drain, which is less than 1/4" (more like 3/16 slope). I can fix this by downsizing the pipe to a 1 1/2" by I don't feel comfortable by doing it.
Hope the image is more clear this time.
 

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the part I dont understand is the magenta line that appears horizontal going from the grey to the wall a couple feet away if thats around a foot off the floor ok if its below floor no good. 3/16 per ft fall is less than code . if choice is barely a 1/4 inch perft with 1 1/4 or just under with 2 inch Id go 2 but dont like it . it could be 1 1/2 shower trap is suffiecent under mass code but not here, Ive done it a time or 2 though. in any case that pink line should not be flat EVER below the floor
 

desithebuilder

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the part I dont understand is the magenta line that appears horizontal going from the grey to the wall a couple feet away if thats around a foot off the floor ok if its below floor no good. 3/16 per ft fall is less than code . if choice is barely a 1/4 inch perft with 1 1/4 or just under with 2 inch Id go 2 but dont like it . it could be 1 1/2 shower trap is suffiecent under mass code but not here, Ive done it a time or 2 though. in any case that pink line should not be flat EVER below the floor
The magenta line is the vent that runs horizontal only about 2-3 inches above the shower drain until it reaches the wall on the right.
 

Jeff H Young

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Thats not good dry vent must rise verticaly until 6 inches above flood level of which it serves before going horrizontal . chsanging pipe size no help.
if your shower drain is only 5 ft 4 to center from the 3 inch why cant you wet vent it from the 3inch you are allowed 5 ft from edge of 3 inch to the weir of the trap definately under 5 foot which is my code but if you have IPC it might be 8 ft. or Boston city or the state might be a differant code but my 5 ft is the strictest. you pulling permits? I hear Mass or at least Boston arent pushovers . no knowledge of area though
 

desithebuilder

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thank you Jeff for all the good info. I think I have to add the vent to the shower since all the vent pipes will tie into the existing vent on the wall on the right ( that round white circle) and this run is longer than 6 ft.
 

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the drawing dosent help isnt a 48 inch shower going into like a 6 ft wide room? why cant a vent come up that wall which isnt on the plans? there are little squares on half the floor ? no wall ?
 

desithebuilder

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Correct, there will be a wall that I have not updated in the plans. I installed the vent up into the wall. However, I had to offset it from the drain line to the wall using a wye combo on 45 degrees+45 degree bend and a 90 elbow. this was the only way I could get it to the wall without drilling new holes thru the joists, which I cannot do because of limited space. This is my progress so far.
 

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desithebuilder

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Correct, there will be a wall that I have not updated in the plans. I installed the vent up into the wall. However, I had to offset it from the drain line to the wall using a wye combo on 45 degrees+45 degree bend and a 90 elbow. this was the only way I could get it to the wall without drilling new holes thru the joists, which I cannot do because of limited space. This is my progress so far.
I hope I got it right. Once I am done, I will have to test the drain line, should I do a pressure test or a water test? If pressure test, is there any kit I can buy?
 

desithebuilder

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I don't think we know the MA plumbing code. You are using a horizontal dry vent for the shower, which may or may not be permitted in Boston. Have you tried to check the code? I tried, but I did not get far. https://www.mass.gov/doc/248-cmr-1000-uniform-state-plumbing-code-0/download
I don't think we know the MA plumbing code. You are using a horizontal dry vent for the shower, which may or may not be permitted in Boston. Have you tried to check the code? I tried, but I did not get far. https://www.mass.gov/doc/248-cmr-1000-uniform-state-plumbing-code-0/download
Can I completely remove the shower vent? Is it better with this horizontal run or without it?
Do you see anything else wrong with this bathroom drains?
 

Jeff H Young

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probebly will work fine but not code legal . one issue is that vent over by the shower cant be horizontal another issue is the double santee should be a double fixture fitting . If you can run a trap arm withen length of your code you might be able to eliminate that vent thats horizontal and dry I never heard of a code anywhere that allows that currently
 

desithebuilder

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probebly will work fine but not code legal . one issue is that vent over by the shower cant be horizontal another issue is the double santee should be a double fixture fitting . If you can run a trap arm withen length of your code you might be able to eliminate that vent thats horizontal and dry I never heard of a code anywhere that allows that currently
mass UPC
probebly will work fine but not code legal . one issue is that vent over by the shower cant be horizontal another issue is the double santee should be a double fixture fitting . If you can run a trap arm withen length of your code you might be able to eliminate that vent thats horizontal and dry I never heard of a code anywhere that allows that currently
The allowed developed length from shower trap to vent per UPC (Applied Plumbing Code in Mass) is 8 FT which I don't have.
So the fact that the wye combo is not horizontal, but rotated with almost 45 degrees upward does not help.
Then I will have to make the shower smaller and bring the wall on the right above the drain line. I will change the santee with a double fixture fitting.
Once I make this changes, it should be up to code and work properly, correct?
Will it be an issue that once the vent pipe goes vertical up to 42" above floor, then it goes horizontal to tie into the existing vent? Is it an issue that the main stack vent does the same thing? Instead of going thru the roof, it goes horizontally and ties in to the existing 4" vent?
Also, what is the recommended test for the drain lines? Air or water? If water, I can get only 42" of water head. If air, what PSI? I have read that 5 psi is required for drain lines.
And weaht about the water supply lines? 100 psi? 125 psi? I intend on using pex pipe type B.
 

desithebuilder

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probebly will work fine but not code legal . one issue is that vent over by the shower cant be horizontal another issue is the double santee should be a double fixture fitting . If you can run a trap arm withen length of your code you might be able to eliminate that vent thats horizontal and dry I never heard of a code anywhere that allows that currently
this is a view of the vent that steps up in relation to the crown weir. I am doing this bathroom myself, I am more concerned about it being fully functional and not give me problems down the road than passing an inspection.

Thank you gents for pointing me in the right direction.
 

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John Gayewski

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mass UPC

The allowed developed length from shower trap to vent per UPC (Applied Plumbing Code in Mass) is 8 FT which I don't have.
So the fact that the wye combo is not horizontal, but rotated with almost 45 degrees upward does not help.
Then I will have to make the shower smaller and bring the wall on the right above the drain line. I will change the santee with a double fixture fitting.
Once I make this changes, it should be up to code and work properly, correct?
Will it be an issue that once the vent pipe goes vertical up to 42" above floor, then it goes horizontal to tie into the existing vent? Is it an issue that the main stack vent does the same thing? Instead of going thru the roof, it goes horizontally and ties in to the existing 4" vent?
Also, what is the recommended test for the drain lines? Air or water? If water, I can get only 42" of water head. If air, what PSI? I have read that 5 psi is required for drain lines.
And weaht about the water supply lines? 100 psi? 125 psi? I intend on using pex pipe type B.
I don't know of an inspector that would fail that vent for the shower at most they might ask for a cleanout on the vent line for access if necessary, but here in my area they are very relaxed on flat venting. We try not to do it, but sometimes the amount of work needed to have a completely vertical vent just outweighs the likelihood that it'll become obstructed. There is a provision that week let your run a vent like that "if structural conditions require it" paraphrased.
 

Reach4

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How hard would it be to run the lavatory drains over to where you have that horizontal dry vent show? That would turn this into a horizontal wet vent.
 

Jeff H Young

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I don't know of an inspector that would fail that vent for the shower at most they might ask for a cleanout on the vent line for access if necessary, but here in my area they are very relaxed on flat venting. We try not to do it, but sometimes the amount of work needed to have a completely vertical vent just outweighs the likelihood that it'll become obstructed. There is a provision that week let your run a vent like that "if structural conditions require it" paraphrased.
I know a few that would call it if not at least rolled up (as I see it is now) which didnt quite show in other posts . However IPC code never allows a flat vent regardless of structural conditions . Mass code I dont know if it follows UPC where some discretion is allowed I think Id let it it go but just dont want to recomend from a sketch to plumb it this way but now looking at what he already has done I think its ok but I cant guarantee his card is getting signed.
I dont want to make thisa too hard on him I wish him well if being inspected , and if not I think function be ok
 
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