Double kitchen sink drain problem

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itsr-ent

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Hi guys,

I have a double kitchen sink that has been working perfectly for the 20+ years I've used it. Earlier this year, the chrome plumbing underneath basically disintegrated in the spot under the bucket in the picture. I quickly took a picture of it for reference, took it all apart, and replaced it with PVC. Everything seemed to work right at first, but we quickly noticed an issue. When putting a lot of water in the left sink all at once (such as filling a bowl and dumping it into the sink while the water is still running), the water would rather come up out of the right sink than drain down. It's not extreme, but definitely wasn't like this before.

I've included a before and after picture. I'm stumped, as it looks like nothing much has changed...the only thing I can see is 1) the tailpieces attached to the sink baskets are now longer, 2) the trap is slightly higher, and 3) the PVC s-trap is a slightly different shape than the chrome one.

Before:

pRYGzH2.jpg



After:

nRsh4fn.jpg



Before everyone says it...I know the issues with S-traps (siphoning and codes requirements). :) If the solution involves converting to a P-trap, then I'm all for it, but this sink with the chrome S-trap worked perfectly like that for probably 50+ years.

If a picture of the plumbing below the floor would help, let me know. It's a full basement with direct access to the pipes. The only thing I did down there was cut off the 1.5" copper 90 with trap adapter (going up through the floor/cabinet) and replaced it with a 1.5" PVC 90 with trap adapter (connected with Ferco coupling to old copper).

Thanks!!
 
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Cacher_Chick

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Understanding that no one wants to tear their house apart to install a proper vent, I would probably do something like this- IMG_20140302_152132.jpg

If all you want to do is stop the backup, switch the tee to a dishwasher tee with an internal baffle. If it still backs up, you have a restriction downstrean.
 
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itsr-ent

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Thanks for the reply! I'm not picturing where the trap would be in the diagram you included.

The Tee I'm using there is called a "baffle tee" on the package. I can't remember if I verified it actually has the baffle inside, but I would assume so.

I think there's enough of the Tee stuck into the S-trap, that I could shorten the tailpieces 2-3" and not have to change the trap position. Or I'm sure there's something that could extend the length of the Tee.

There is a vent near the pipe in the basement. The plumbing goes down through the cabinet, through the subfloor, turns right (the PVC 90 attached to copper via Fernco), then goes about 2-3 feet, then there's a connection up through the attic to the vent stack and the plumbing continues around the perimeter of the basement. So, the vent is within 4 feet or so of the sink, but I know that with a P-trap it is supposed to be vented BEFORE it goes down.
 

Cacher_Chick

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Yes, the p-trap would go directly under the center outlet. The vent connection at the sanitary tee cannot be below the weir of the trap for the vent to function properly.
 

itsr-ent

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Yes, the p-trap would go directly under the center outlet. The vent connection at the sanitary tee cannot be below the weir of the trap for the vent to function properly.

Ah, that makes sense. I'll wait to see if anyone has other suggestions, but I think right now I'll plan to bring full 1.5" PVC up from the basement (rather than have the trap adapter down below the floor like it is now) to a sanitary tee, then continue up from the sanitary tee and put an AAV (Studor mini-vent) as high as possible. Then I'll add more 1.5" PVC to the sanitary tee (horizontally) to get closer to the center outlet, then attach a trap adapter for the P-trap to connect to.

When I switch to a the center outlet, is there a proper tailpiece length when connecting to the sink? I definitely won't want the tailpieces as long as they are now, as the P-trap in the middle would be low enough to prevent storing things in the cabinet.

Thanks for your help so far!
 
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Cacher_Chick

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What you propose is fine. The tailpieces can be cut down, 3-4" is fine. The only other thing you might consider is putting in a disposer, which would require changing the drain configuration again.
 

itsr-ent

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Thanks, my only other question/idea is about leaving the "non-center" outlet piping in place, and using 2x 45's to get the 1.5" PCV from the basement closer to the back wall, so the AAV is up in the back right corner, and the p-trap is off to the right side, freeing up more space in the cabinet. I'm not sure if that's a good idea or if I'm just making it unnecessarily more complicated.

I couldn't draw it so it looks farther away, but kind of like this:

rRQwXSp.jpg
 

hj

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An AAV is NOT going to make your sinks drain better, because your description implies a "positive pressure" problem and AAVs are useless to solve those, (in fact they can cause or contribute to them). The only thing it will do is give you something to remove and prove that the sink WILL drain without it.
 

Cacher_Chick

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I am not sure that you have enough room there to keep the end outlet drain and install a p-trap and sanitary tee.
 

itsr-ent

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An AAV is NOT going to make your sinks drain better, because your description implies a "positive pressure" problem and AAVs are useless to solve those, (in fact they can cause or contribute to them). The only thing it will do is give you something to remove and prove that the sink WILL drain without it.

Hmm, do you have any idea why I might be having this issue with the new PVC but definitely wasn't having it with the chrome plumbing?

I'm still thinking it has to do with the tailpiece length. The trap is closer to the horizontal piece now, so water fills up the second tailpiece, where as before the lower trap just gave it a little more time to pass through before the level went up the other tailpiece.
 
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Jim Mills

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Get rid of that baffle Tee. They're not intended to be used in a vertical position like that, and are lousy in any position IMO. Also, maybe a chunk of the old rusty pipe broke off & is lodged in the drain line somewhere. Might try cabling it. Prolly just the baffle tee though...
 
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Cacher_Chick

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PlumbingTees.jpg

Jim, how would the proper baffle tee cause water to come up in the opposite sink? This is exactly what a baffle tee is intended to prevent.
 
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hj

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quote; Get rid of that baffle Tee. They're not intended to be used in a vertical position like that, and are lousy in any position

I do not know HOW you normally use a baffle tee, but the most common usage IS in a vertical position. They would have limited value in a horizontal line. The could be several reason why the old drain worked, but they would have nothing to do with it being metal rather than plastic. I am assuming that you have a "double trap" situation, for some reason, and the former drain had enough "force" or velocity to push its way through it. Years ago, Delta made a plastic 3,5 gpf one piece toilet. The supply house sold it to a customer who installed it himself in place of his old one. It would not flush, so they asked me to check it out. When I removed the toilet, there was water in the pipe, because it was installed over a "P" trap. The new toilet did not create enough force to push through the second trap, but the old one, which I reinstalled, did and worked perfectly.

Cacher, what you call a "pressure tee" is a "vent tee" and they ARE permitted in vent portion of a DWV system. I have never seen sch. 40 end or center outlet tees with a baffle in them
 
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itsr-ent

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Get rid of that baffle Tee. They're not intended to be used in a vertical position like that, and are lousy in any position IMO. Also, maybe a chunk of the old rusty pipe broke off & is lodged in the drain line somewhere. Might try cabling it. Prolly just the baffle tee though...

I don't know much about plumbing, but the kit I used has a diagram of the tee being installed exactly as pictured. I did think about the chuck of pipe in the drain line when it first disintegrated...so I sent my inspection camera in when I had it all apart to verify it's all clear. Once I verified it was clear, I installed all the PVC.

quote; Get rid of that baffle Tee. They're not intended to be used in a vertical position like that, and are lousy in any position

I do not know HOW you normally use a baffle tee, but the most common usage IS in a vertical position. They would have limited value in a horizontal line. The could be several reason why the old drain worked, but they would have nothing to do with it being metal rather than plastic. I am assuming that you have a "double trap" situation, for some reason, and the former drain had enough "force" or velocity to push its way through it. Years ago, Delta made a plastic 3,5 gpf one piece toilet. The supply house sold it to a customer who installed it himself in place of his old one. It would not flush, so they asked me to check it out. When I removed the toilet, there was water in the pipe, because it was installed over a "P" trap. The new toilet did not create enough force to push through the second trap, but the old one, which I reinstalled, did and worked perfectly.

Cacher, what you call a "pressure tee" is a "vent tee" and they ARE permitted in vent portion of a DWV system. I have never seen sch. 40 end or center outlet tees with a baffle in them

No obvious double trap...basement is full height with open access to all the pipes. I'll take a picture, but it just comes down through the floor, turns 90 degrees and goes around the basement wall (with a slight slope the whole way) to the main stack.
 

Jim Mills

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The baffle Tee that I am referring to is what Cacher_chick referres to as a "center outlet" tee in the above post. Not a Schedule 40, but the polyethylene ones that come in the typical slip joint kitchen drain kits. The ones I have seen create a severe restriction, and something as small as a banana sticker can nearly clog one. When placed in a vertical position, and a rapid flow of water is sent down, say draining a full sink of water, half the water wants to go down the drain, while the other half goes up into the other sink. The shorter the tailpieces, the more water will go up into the other sink.

When placed horizontally, these "center outlet" tee's create slow draining sinks.
 

itsr-ent

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The baffle Tee that I am referring to is what Cacher_chick referres to as a "center outlet" tee in the above post. Not a Schedule 40, but the polyethylene ones that come in the typical slip joint kitchen drain kits. The ones I have seen create a severe restriction, and something as small as a banana sticker can nearly clog one. When placed in a vertical position, and a rapid flow of water is sent down, say draining a full sink of water, half the water wants to go down the drain, while the other half goes up into the other sink. The shorter the tailpieces, the more water will go up into the other sink.

When placed horizontally, these "center outlet" tee's create slow draining sinks.

So from that diagram, I'm supposed to have an "End outlet tee" (with internal baffle) there, but you think it's a "Center outlet tee" (which I can certainly see would cause an issue). Like I said, that whole horizontal piece and tee were a kit...this one to be exact: http://www.lowes.com/pd_25032-143-125-16WK_0__?productId=1071581

They sell the Tee's separately, but they seem to be the same one that's in the kit. Next time I'm at the store, I'll see what the baffle looks like. However, I would assume the manufacturer would correctly include end outlet tees in the end outlet kit and center outlet tees in the center outlet kit. If not, that's pretty bad!

It's possible the old chrome Tee didn't have a baffle at all and that's why it didn't have the issue. I didn't dissemble it that far, and it was thrown away already so I can't look.
 
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hj

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quote; No obvious double trap.

"double traps" can be caused by "conditions" not necessarily a "physical double trap". The baffle tee he used is NOT a center outlet one, (and no one has even mentioned anything about using a center outlet baffle tee), and in normal situations it would be almost impossible to use one in a vertical location, unless you created some kind of kludge to attach to the "male" tailpiece pipe. If you install an AAV, and the sink will probably still not drain properly, remove it and then it should drain. If this is what happens, then you DO have a "double trap" condition somewhere. If the pipe the sink connects to has water in it, THAT would cause the "double trap".
 
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MikePlummer

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the obvious reason that the water backs up into the other sink is that it is not draining fast enough - most likely a partial blockage or restriction. that s-trap arrangement looks look it would be more restrictive than the old chrome assembly
 

itsr-ent

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Thanks for the help with this, everyone. Unfortunately it turned out to be a larger issue. The run for this sink (in the basement) is around 35-40 ft. of 1.5" Copper. I took the trap out under the sink and water just didn't seem to be going down the pipe correctly (if I poured it in). I snaked it with a 1/4" cable auger, but I only had 25' and it wasn't enough to open it up. Opened the pipe in the basement and found a huge amount of buildup in the last 15' of pipe. The 1/4" bulb auger cable just wasn't enough, so I had someone use a larger auger and it solved the issue (for now).

The pipe is really old and I'm sure not 100% cleaned out. At some point I'll cut it a foot from where it connects to the main stack, solder on a 1.5" copper female adapter and adapter to 1.5" PVC with a 1.5" PVC male adapter (I think this is the best way to do it to avoid using a weak female PVC fitting), and run the 35-40' of 1.5". Getting the 1/4" per foot pitch might be difficult, but it does turn 90 degrees to follow the wall.

I'll have to solder on another 1.5" threaded adapter closer to the sink to connect to the existing copper vent pipe that goes up the wall. Sounds like a fun project. :eek:
 
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