First post. Looking for some recommendations to fix persistent drain backups with some non-slab busting solutions. This is a 1969 build and all under slab drainpipe is cast iron. We seem to have an issue toward the end of this branch with frequent backups in the shower drain (rough-in) and the floor drain (other side of wall). Drainpipe was scoped and cleaned a few years back from the toilet forward (towards the main), and all was in good shape. Neighbors with similar setups have suggested that the kitchen sink drain at the end of the branch is the culprit and suggest rerouting this drainpipe forward on the branch to tee into the 2" toilet drain vent. Can this be done without the change creating a multi-story wet vent? Are there other solutions that we should consider as well? Thanks!
DWV - Can I drain my upper floor 2" kitchen sink into my basement 2" toilet vent
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Thinking about this a bit more.
If the kitchen sink drain were to be tied into the toilet vent, is there a risk of a single sink with a 2" drain pulling the trap on a toilet with a 3" drain if the horizontal run is about 10' and I use a wye to tie it in? All other connections on this branch are independently dry vented. Based on reading the other posts - I don't think this would pass code as a multi-story wet vent, but would this still sufficiently work to alleviate our issues?
On that same thought - would it be better to slow down the water from the sink drain as it enters the wet vent area? I would think this would allow the water to spread out and take up less room in the pipe - allowing for more air to displace. I would still adhere to the min 1/4" per foot drop, but would not exceed that in this case. What do you think?
Thanks!
If the kitchen sink drain were to be tied into the toilet vent, is there a risk of a single sink with a 2" drain pulling the trap on a toilet with a 3" drain if the horizontal run is about 10' and I use a wye to tie it in? All other connections on this branch are independently dry vented. Based on reading the other posts - I don't think this would pass code as a multi-story wet vent, but would this still sufficiently work to alleviate our issues?
On that same thought - would it be better to slow down the water from the sink drain as it enters the wet vent area? I would think this would allow the water to spread out and take up less room in the pipe - allowing for more air to displace. I would still adhere to the min 1/4" per foot drop, but would not exceed that in this case. What do you think?
Thanks!
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I do not like or ever used a WETVENT other then for an acid waste system
Having a kitchen sink waste that carries grease and reduces the vent internal size over time will lead to bigger problems'
Shower min size should be 2"
Having a kitchen sink waste that carries grease and reduces the vent internal size over time will lead to bigger problems'
Shower min size should be 2"
Thanks for your feedback!
That's a great point, and an important consideration. Would it be possible and perhaps wise then if we were to proceed with this less than ideal solution to put a clean out at this connection so we can better maintain the grease and fat build up in this area over time?
That's a great point, and an important consideration. Would it be possible and perhaps wise then if we were to proceed with this less than ideal solution to put a clean out at this connection so we can better maintain the grease and fat build up in this area over time?
wwhitney
In the Trades
I have no idea if moving the kitchen drain will help you. It would seem to me you could add a cleanout to the kitchen sink drain stack to let you rod it and the building drain upstream of the WC. Is there no cleanout already at the upstream end of the building drain? Possibly outside?
Moving the kitchen sink to the toilet vent is not allowed, it would be creating a wet vent that is not compliant with the rules (no interstory wet vents, wet vents for bathroom fixtures only).
If moving the kitchen drain would actually be useful, you can run it across the wall above the horizontal 2" vent, turn down after the lav, and join the lav drain below the san-tee.
Cheers, Wayne
Moving the kitchen sink to the toilet vent is not allowed, it would be creating a wet vent that is not compliant with the rules (no interstory wet vents, wet vents for bathroom fixtures only).
If moving the kitchen drain would actually be useful, you can run it across the wall above the horizontal 2" vent, turn down after the lav, and join the lav drain below the san-tee.
Cheers, Wayne
wwhitney
In the Trades
For better or worse, the IPC allows a 1-1/2" shower drain for up to 5.7 gpm of showerheads. Personally I would prefer a 2" shower or tub drain.
Cheers, Wayne
Great replies - thank you.
Good to know about the shower drain size, especially as we purchase our fixtures. Not sure why its rough in is 1.5" - wouldn't have been room for a tub here anyway.
Wayne -
There is no cleanout on this branch at all. This is an interior townhouse, and that block wall is the party wall. I think adding a clean-out here is a must in all cases.
Understand that issue with code on the multi-story wet vent (and not from outside this bathroom group). That's an interesting idea to join it to the lav below the san-tee. Is there an issue with connecting this 2" drain to the 1.5" lav drain? Would it be better to connect it to the first lav drain (the laundry tub) or the second (the bathroom sink)?
Thanks again!
Good to know about the shower drain size, especially as we purchase our fixtures. Not sure why its rough in is 1.5" - wouldn't have been room for a tub here anyway.
Wayne -
There is no cleanout on this branch at all. This is an interior townhouse, and that block wall is the party wall. I think adding a clean-out here is a must in all cases.
Understand that issue with code on the multi-story wet vent (and not from outside this bathroom group). That's an interesting idea to join it to the lav below the san-tee. Is there an issue with connecting this 2" drain to the 1.5" lav drain? Would it be better to connect it to the first lav drain (the laundry tub) or the second (the bathroom sink)?
Thanks again!
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wwhitney
In the Trades
Looking at your picture I disbelieved that the lav drain is 1.5", it looks the same size as the 2" toilet vent. Maybe double check, or maybe it's the perspective that is confusing me. Absolutely you can't downsize the drain, so if you don't have any 2" drains rising out of the slab (as opposed to vents), my idea wouldn't work.
I would think a cleanout is required at the kitchen sink drain or the stack below it, for precisely this reason. You've checked the WC fixture drain and the building drain downstream of it, but you haven't checked the building drain upstream of it, which could be where you are having the problem.
So I suggest adding a cleanout (in a location where it can remain accessible after you build your shower) and rod/camera the kitchen sink drain and building drain from there. That may solve your problems. And if it doesn't reveal any blockages or geometry problems, you'll have to look elsewhere for the cause of your backups. I'm dubious about the idea of moving the kitchen drain being an effective way to address your issues.
Alternatively, if there's another unit on the other side of the block wall, is the building drain continuous through there? Perhaps there's already a cleanout at the far end of that unit? If it's a common building drain, is that the responsibility of the HOA? With a common building drain, you could be experiencing backups caused by blockages from waste from another unit.
Cheers, Wayne
Thanks Wayne -
Agreed - in the picture it's a bit deceiving. I will double check to be sure - but it does look like a reducer on the relief vent between the toilet and the lav vents.
Also agree for the need to have a cleanout. If we don't move the kitchen drain, I'll add one behind that 2x6 wall with an access panel from the laundry room.
These homes are independently plumbed - unfortunately (or fortunately) there are no continuous building drains.
Two neighbors who have simply moved the kitchen sink drain forward on the branch have alleviated this issue - so I think it has some merit. One of the neighbors tied into the toilet vent (as mentioned above), and the other had a slightly different floorplan that allowed them to carry the kitchen drain into the main stack. We can't do that as it's 20' away and blocked by stairs, ducts, and other building components.
Thanks again Wayne.
Agreed - in the picture it's a bit deceiving. I will double check to be sure - but it does look like a reducer on the relief vent between the toilet and the lav vents.
Also agree for the need to have a cleanout. If we don't move the kitchen drain, I'll add one behind that 2x6 wall with an access panel from the laundry room.
These homes are independently plumbed - unfortunately (or fortunately) there are no continuous building drains.
Two neighbors who have simply moved the kitchen sink drain forward on the branch have alleviated this issue - so I think it has some merit. One of the neighbors tied into the toilet vent (as mentioned above), and the other had a slightly different floorplan that allowed them to carry the kitchen drain into the main stack. We can't do that as it's 20' away and blocked by stairs, ducts, and other building components.
Thanks again Wayne.
Tuttles Revenge
In the Trades
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Seems odd that the drain should be clogging at all being ABS. Maybe its not graded or lots its grade somehow. Or maybe just too much grease going down? Moving it downstream of the bathroom drain and especially the toilet seems like a decent approach as it will be entering a larger diameter pipe and have other fixtures to wash it down (tho that should never be necessary.) Is that a concrete slab? I would suggest opening the slab and bringing up a new 2" dedicated drain to the right of the lav/sink drain and making a legal and proper sized connection.
Wet venting between floor isn't allowed, also a kitchen sink can't be part of a wet vent.
Thanks everyone for the suggestions and comments -
Mr Tee -
Thanks for the tip on the combination. That was original to the '69 build - maybe it was code then - or maybe that was their last ABS fitting in the bag.
Terry -
Wet venting is an interesting topic. One that seems to come up often on these forums. Thanks for sharing the diagram. Certainly don't want to siphon my traps and fill my house with sewer gas - at least not today.
Tuttles Revenge -
It is concrete slab with cast-iron underneath. I think you are right though - this is likely due to a confluence of multiple issues. Grease/fat from the kitchen, lint from the laundry, and no easily accessible cleanout for this branch under the slab. It's also possible there are some other slope or snag issues in the under slab drainpipe as well. I like the idea of having a new dedicated 2" connector - but that drainpipe is offset from the vent by about 3-4", which is behind this wall with the vents - and it would be an even larger endeavor to break into that area in the other room.
Wayne -
Checked up on that lav drain/vent - and it was indeed 1.5", but coming out of the slab it was reduced from a 2" connector, and under the slab the wye connectors are all 3" cast. So went a bit further with this idea and pulled that 1.5" ABS out of the larger hub, and replaced with 2" PVC. Then rerouted the kitchen drain from the end of the branch to the new 2" drain under the new lav sanitary tee.
Sylvan -
Turns out that shower drain is 2" ... need to recheck my eyes.
We did get into the slab to move the flange, and the shower drain - and a little more exploration. From what we can see, the pipes look ok, though the 3" cast iron drain connector that was cut out from the kitchen line had a significant amount of soft waste in it (50-60% filled). While we were here we also put in a cleanout at the end of the branch drain where the kitchen drain had previously been routed for good measure (and maintenance).
Pictures - because plumbing is awesome:
Under slab - just soft dirt down here.
New 2" lav drain (left) and 2" kitchen drain (right).
New clean-out extension.
Mr Tee -
Thanks for the tip on the combination. That was original to the '69 build - maybe it was code then - or maybe that was their last ABS fitting in the bag.
Terry -
Wet venting is an interesting topic. One that seems to come up often on these forums. Thanks for sharing the diagram. Certainly don't want to siphon my traps and fill my house with sewer gas - at least not today.
Tuttles Revenge -
It is concrete slab with cast-iron underneath. I think you are right though - this is likely due to a confluence of multiple issues. Grease/fat from the kitchen, lint from the laundry, and no easily accessible cleanout for this branch under the slab. It's also possible there are some other slope or snag issues in the under slab drainpipe as well. I like the idea of having a new dedicated 2" connector - but that drainpipe is offset from the vent by about 3-4", which is behind this wall with the vents - and it would be an even larger endeavor to break into that area in the other room.
Wayne -
Checked up on that lav drain/vent - and it was indeed 1.5", but coming out of the slab it was reduced from a 2" connector, and under the slab the wye connectors are all 3" cast. So went a bit further with this idea and pulled that 1.5" ABS out of the larger hub, and replaced with 2" PVC. Then rerouted the kitchen drain from the end of the branch to the new 2" drain under the new lav sanitary tee.
Sylvan -
Turns out that shower drain is 2" ... need to recheck my eyes.
We did get into the slab to move the flange, and the shower drain - and a little more exploration. From what we can see, the pipes look ok, though the 3" cast iron drain connector that was cut out from the kitchen line had a significant amount of soft waste in it (50-60% filled). While we were here we also put in a cleanout at the end of the branch drain where the kitchen drain had previously been routed for good measure (and maintenance).
Pictures - because plumbing is awesome:
Under slab - just soft dirt down here.
New 2" lav drain (left) and 2" kitchen drain (right).
New clean-out extension.
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wwhitney
In the Trades
Looks like you've been busy, very nice. What's the fitting between the new lav/kitchen wye and the lav san-tee?
On the cleanout, how are you going to provide access? I think a 45 off the riser with a spigot end cleanout adapter in it could be a nice approach.
Since your kitchen drain seems to create an accumulation of soft muck over time, did you provide access to cleanout the kitchen drain itself? Or is your diagnosis that it just accumulates on the rough cast iron, not on the plastic, and so introducing it downstream on the cast iron building drain will let the other fixtures wash the cast iron to prevent accumulation? Plus the new cleanout will let you access all the cast iron building drain.
Cheers, Wayne
On the cleanout, how are you going to provide access? I think a 45 off the riser with a spigot end cleanout adapter in it could be a nice approach.
Since your kitchen drain seems to create an accumulation of soft muck over time, did you provide access to cleanout the kitchen drain itself? Or is your diagnosis that it just accumulates on the rough cast iron, not on the plastic, and so introducing it downstream on the cast iron building drain will let the other fixtures wash the cast iron to prevent accumulation? Plus the new cleanout will let you access all the cast iron building drain.
Cheers, Wayne
Thanks Wayne -
The fitting between the wye and the sanitary tee on the lav drain is an additional cleanout just for this connection. Now could we also add a laundry standpipe in here as well?
Access for both cleanouts will be from the laundry/utility room behind this wall. Were you thinking to add the 45 flush with the drywall, or facing up?
The kitchen drain does create an accumulation of soft muck over time, that is certain. Based on what we pulled out, I think it accumulates on both the plastic and cast iron, but worse on the latter. What's interesting is that I don't think we abuse our drains - especially in consideration of our basement issues. We mostly compost and use our garbage disposal sparingly. Years ago, I put Insinkerator's evolution disposal hoping that would break up any remnant food debris into smaller pieces that could easily be passed through the drain, but now I'm not sure if that hurts or helps this situation. Maybe I should have put in their enzyme treatment model.
We did not add a cleanout for the kitchen drain itself yet, but definitely will do that as well. That should cover most of the bases.
I'm also hopeful that the new horizontal run for the kitchen drain (above the vent run) will allow the water to carry most of the debris further down the line. We shall see.
Thanks again Wayne.
The fitting between the wye and the sanitary tee on the lav drain is an additional cleanout just for this connection. Now could we also add a laundry standpipe in here as well?
Access for both cleanouts will be from the laundry/utility room behind this wall. Were you thinking to add the 45 flush with the drywall, or facing up?
The kitchen drain does create an accumulation of soft muck over time, that is certain. Based on what we pulled out, I think it accumulates on both the plastic and cast iron, but worse on the latter. What's interesting is that I don't think we abuse our drains - especially in consideration of our basement issues. We mostly compost and use our garbage disposal sparingly. Years ago, I put Insinkerator's evolution disposal hoping that would break up any remnant food debris into smaller pieces that could easily be passed through the drain, but now I'm not sure if that hurts or helps this situation. Maybe I should have put in their enzyme treatment model.
We did not add a cleanout for the kitchen drain itself yet, but definitely will do that as well. That should cover most of the bases.
I'm also hopeful that the new horizontal run for the kitchen drain (above the vent run) will allow the water to carry most of the debris further down the line. We shall see.
Thanks again Wayne.
wwhitney
In the Trades
On the 45, I was thinking of an access panel that when you remove it, the 45 points up and out of the wall. So a snake entering it only turns 45 degrees to go vertical. I don't have any direct experience in designing such things.
Your plumbing code, the IPC, requires that a laundry standpipe drain increase in size to 3" as soon as it joins another fixture's drain. So if you want to add a laundry standpipe to one of the existing drain risers from the slab that serve another fixture, you need to enlarge that drain riser to 3". Which should be possible as you stated the cast iron fittings under the slab are all 3".
There is also an allowance for a laundry sink and a laundry standpipe to share a 2" trap (the sink drains into the standpipe without a trap), so if you enlarged your 1.5" laundry sink drain to 2", that would be an option, as long as you don't add any fixtures between the 2" trap and your building drain below the slab.
Cheers, Wayne
Your plumbing code, the IPC, requires that a laundry standpipe drain increase in size to 3" as soon as it joins another fixture's drain. So if you want to add a laundry standpipe to one of the existing drain risers from the slab that serve another fixture, you need to enlarge that drain riser to 3". Which should be possible as you stated the cast iron fittings under the slab are all 3".
There is also an allowance for a laundry sink and a laundry standpipe to share a 2" trap (the sink drains into the standpipe without a trap), so if you enlarged your 1.5" laundry sink drain to 2", that would be an option, as long as you don't add any fixtures between the 2" trap and your building drain below the slab.
Cheers, Wayne
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