left drain pipe open after cutting it


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Old 04-06-18, 04:40 PM
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left drain pipe open after cutting it

Hi.

I'm removing an old laundry sink and couldn't get the drain tube out after loosening nut below, so I used a hacksaw to cut the 1 1/2 pipe that the drain tube attached to. Right now there's water in it , but the pipe is coming UP so nothing is getting out. Is this ok to leave for the weekend like this?

Do I have to worry about sewer gas or anything? I'm going to remove all this and put in a modern p trap, etc. The plumber who was over for something else told me to leave the 1 1/2 white pipe in back and tie into that with my new p trap setup.

He told me to cut basically right at the end of this setup on the right and use a 1/ 1/2 to 1 1/4 adapter. When I cut that pipe after the last bend there on the right is water going to come rushing out? I'm not cutting the white pipe in back, but a few inches BEFORE that of course to attach my adapter, etc.

I assume that the large drain pipe that this goes into to the furthest right is the main house drain pipe for everything.


The 1 1/2 pvc in back drains from another sink (which I'm doing over also) in back of this wall in a small basement bathroom area. So it's basically two sinks adjacent to each other that share the same drain pipe.
 
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Old 04-06-18, 09:42 PM
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Hi there,

I'll try to break this apart as best as I can.
Right now there's water in it , but the pipe is coming UP so nothing is getting out. Is this ok to leave for the weekend like this?
Yes that should be fine. You won't get any sewer gas as the water that is still in your existing trap is protecting you from that.

He told me to cut basically right at the end of this setup on the right and use a 1/ 1/2 to 1 1/4 adapter. When I cut that pipe after the last bend there on the right is water going to come rushing out? I'm not cutting the white pipe in back, but a few inches BEFORE that of course to attach my adapter, etc.
There may be a little, because your existing trap (the greyish cylinder) will have some water in it still. Be careful when you do cut it and go to take out the existing trap setup. Make sure to keep it upright as best as you can or keep it above something to catch the gross grey water.

There shouldn't be any in that white 1-1/2" pvc in the back as it drains directly into your building stack (you're correct it is the large on at the back). Don't be surprised when you do cut it if some water drips as there is always a little water sitting in the bottom of a pipe. If you are using a reciprocating saw to cut your pipe, it will spray even small amounts of water around making it seem like there is a lot more than there really is.

For your new fixture, if it has an 1-1/4" drain outlet, then yes you'll attach a reducer and your new trap. Note, when you come off that 1-1/2" PVC at the back and go to your new trap, don't jump up like it is now. That will not vent properly. Just come off horizontally (with 1/4" grade) to your trap and up into your sink.

Personally, if your new laundry sink drain outlet is 1-1/4", I would still do your trap in 1-1/2" since the wye in the back is 1-1/2". Laundry sinks can hold and drain a lot. Where I live the plumbing code requires 1-1/2"
 
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Old 04-06-18, 10:04 PM
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Originally Posted by kellogs View Post
Hi there,

I'll try to break this apart as best as I can.
Yes that should be fine. You won't get any sewer gas as the water that is still in your existing trap is protecting you from that.

There may be a little, because your existing trap (the greyish cylinder) will have some water in it still. Be careful when you do cut it and go to take out the existing trap setup. Make sure to keep it upright as best as you can or keep it above something to catch the gross grey water.

There shouldn't be any in that white 1-1/2" pvc in the back as it drains directly into your building stack (you're correct it is the large on at the back). Don't be surprised when you do cut it if some water drips as there is always a little water sitting in the bottom of a pipe. If you are using a reciprocating saw to cut your pipe, it will spray even small amounts of water around making it seem like there is a lot more than there really is.

For your new fixture, if it has an 1-1/4" drain outlet, then yes you'll attach a reducer and your new trap. Note, when you come off that 1-1/2" PVC at the back and go to your new trap, don't jump up like it is now. That will not vent properly. Just come off horizontally (with 1/4" grade) to your trap and up into your sink.

Personally, if your new laundry sink drain outlet is 1-1/4", I would still do your trap in 1-1/2" since the wye in the back is 1-1/2". Laundry sinks can hold and drain a lot. Where I live the plumbing code requires 1-1/2"
Thanks for all the info!

It's not really a laundry sink though. It's more of a utility sink that I use to wash paint brushes occasionally and that's really all. You can see the sink in the picture, it's more of a standard type sink I think. Does it really have to be 1 1/2 drain for code?

Also, the plumber said something about using a Y PIPE? Do you think I'll need that?

Basically, the sink on the other side of this wall is going to be a small bathroom vanity sink and he said I just have to attach to this white pvc pipe on the other side of the wall (and of course install another p trap over there, etc.

When i do the cut on the 1 1/2 I'll most likely use a hacksaw. Do I clean up the birs, etc before attaching the primer and cement, etc? I did a drain pipe upstairs in the bathroom and it came out perfect maybe a year ago, but I don't remember much about the cementing process. I do still have a can of the purple and (gray?) stuff though .... hopefully it's still good.

Got my projects cut out for next week!
 
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Old 04-06-18, 11:54 PM
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It's not really a laundry sink though. It's more of a utility sink that I use to wash paint brushes occasionally and that's really all. You can see the sink in the picture, it's more of a standard type sink I think. Does it really have to be 1 1/2 drain for code?
You should, yes. Zooming in on your first picture, it looks like the existing pipe coming down from your sink is labelled 1-1/2" (it's cut right on the size label). You cannot reduce pipe size in direction of flow in plumbing.

Also, the plumber said something about using a Y PIPE? Do you think I'll need that?
I'm not sure what the context is here. A Y fitting? If so, you already have a Y in the white pipe at the back (before it drains into your building stack).

When i do the cut on the 1 1/2 I'll most likely use a hacksaw. Do I clean up the birs, etc before attaching the primer and cement, etc?
Yes you should. Burrs may push the glue out of the fitting when you push the pipe into fitting. As far as I know glue will only 'go bad' if it freezes. Just make sure that you're using the correct glue / primer (purple stuff) for the type of pipe. The bottles should all say what they're for.
 
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Old 04-07-18, 01:26 AM
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Originally Posted by kellogs View Post
You should, yes. Zooming in on your first picture, it looks like the existing pipe coming down from your sink is labelled 1-1/2" (it's cut right on the size label). You cannot reduce pipe size in direction of flow in plumbing.

I'm not sure what the context is here. A Y fitting? If so, you already have a Y in the white pipe at the back (before it drains into your building stack).

Yes you should. Burrs may push the glue out of the fitting when you push the pipe into fitting. As far as I know glue will only 'go bad' if it freezes. Just make sure that you're using the correct glue / primer (purple stuff) for the type of pipe. The bottles should all say what they're for.
Thanks Kellogs, but I'm going to put a whole new drain tube coming down that I bought and it's 1 1/4 inch. I think the plumber said to get rid of all the 1 1/2, save for the rear pipe.

On second thought, maybe I can just keep the drain tube that's in that sink. So do I just keep the whole pipe and trap 1 1/2?

How do I connect the areas that I cut and stuff when I cut the old pipe out?

Do they have ways of attaching 1 1/2 to 1 1/2?

Sorry, new to plumbing.
 
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Old 04-07-18, 11:19 AM
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On second thought, maybe I can just keep the drain tube that's in that sink. So do I just keep the whole pipe and trap 1 1/2?
I would for sure.
How do I connect the areas that I cut and stuff when I cut the old pipe out?

Do they have ways of attaching 1 1/2 to 1 1/2?
Yes you'll need a coupling for this. You can find them with other DWV PVC fittings at your local hardware store. There's a link below for an example.
https://www.homedepot.com/p/1-1-2-in...D112/100342772
Example of where the coupling with go
https://i.imgur.com/oQmnfrM.jpg

Now I really feel I should mention that the setup you have and how it is drawn in that picture is not legally vented. Legally, one of those sinks would need it's own vent tying into your house's venting system (pictured below). I'm not going to tell you it's not going to work since it looks like you have had it like that for years and not had an issue. That being said, a plumbing inspector (maybe a building inspector as well, depending on how well they know plumbing code) would not pass that. I would talk to your local plumber again to see what they say as code may vary between locations. I would assume that this would be the same however.
"Legal" method of venting your sink
https://i.imgur.com/6bIKWpP.jpg
 
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Old 04-08-18, 07:40 PM
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Thanks for all the info Kellogs!

The venting system thing I'm afraid "has got me". I don't even know where or what it is in this house.

I just read that if a fixture is located within 5 feet of the waste stack (which both of my bathroom ones are) they don't require a vent often times.

Would I actually SEE the vent or is it somewhere past the main?

The plumber who was over just told me to add a trap etc, didn't say anything about adding vents and when I redid the upstairs vanity I never put in a vent I just attached from the p trap to the 1 1/2 PVC coming out from the wall under the vanity.

For the drain pipe on the utility sink that is pictured below I want to come down from the drain tube in the sink and go to a P trap and then have an extension tube that'll extend the a elbow that'll connect into the end of the pipe in back. Is this good? It'll all be 1 1/2 inch plastic pipe correct? I don't need to use actual PVC right?

Thanks
 

Last edited by Brian1900; 04-08-18 at 09:00 PM.
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Old 04-09-18, 08:48 AM
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I'm going to assume that the vent stack is past the wall? I believe I have a pipe coming out on my roof I'll have to check.
 
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Old 04-09-18, 10:06 AM
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The vent is provided by your main stack.

Based on more recent codes, the main stack is a wet vent, and you'd technically need a separate vent - BUT, if everything has been working reasonably well, I wouldn't go through the hassle of venting and just connect it up.

I would cut out the existing drum trap, add a trap adapter to the existing piping. Then use slip fittings for the new P-Trap into the existing piping. I wouldn't even cut any of the horizontal pipe along the back wall - no need.

Keep it simple!
 
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Old 04-09-18, 02:16 PM
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Originally Posted by Zorfdt View Post
The vent is provided by your main stack.

Based on more recent codes, the main stack is a wet vent, and you'd technically need a separate vent - BUT, if everything has been working reasonably well, I wouldn't go through the hassle of venting and just connect it up.

I would cut out the existing drum trap, add a trap adapter to the existing piping. Then use slip fittings for the new P-Trap into the existing piping. I wouldn't even cut any of the horizontal pipe along the back wall - no need.

Keep it simple!
Thanks, the plumber told me the same thing. He said leave the pipe in back. That pipe comes from the vanity in back that is in the small bathroom, so I'll tie in at the end to that one.

What pipes do I need though? I bought a 1 1/2 p trap that comes with the trap and extension tube I think.

Should I cut RIGHT after the drum and keep the elbow there that go's down OR should I cut AFTER the elbow to the right right before the BACK pipe and add my own elbow. The plumber said cut after the elbow to the right, but he may have been not thinking. It looks like it would be SIMPLER to just cut right to the right of the trap?

Also, when I add an extension from the P trap to the far right to connect into the back pipe should it slant slightly downwards? Just eye it basically?

On the other side (through the wall where the back pipe is coming out) I believe it's a piece of 1 1/2 PVC that I cut the old metal pipe off. I'm installing new 1 1/4 p trap, etc.

Do I need a 1 1/2 to 1 1/4 REDUCER? Is that what it's called? Am I right that this reducer will cement to the PVC and then have a slip type joint to the 1 1/4 extension that will attach to the p trap for the bathroom sink behind the wall?
 
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Old 04-10-18, 09:32 AM
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I'm thinking of cutting right after the DRUM trap in the pic below and then attaching there. Is that ok?
 
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Old 04-10-18, 03:37 PM
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Does this look ok?


The smaller vanity is the small bathroom vanity that I just installed on the other side of the wall. I realize in the larger vanity I most likely could've tied in earlier to the left on the rear pipe, but didn't feel like going through all the hassle. These are just put in rough and only the trap adpaters are glued in on the end. This makes 2 pipes and is a little redundant. Hope it's ok ....

Should I cut somewhere after the elbow on the left coming from the wall and then install a Y to share the back pipe or does it matter?

The rear pipe connects through the wall to the vanity in the second and third pictures.
 
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Last edited by Brian1900; 04-10-18 at 04:00 PM.
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Old 04-10-18, 04:13 PM
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Doing back-to-back bathrooms reminds me of a house I sold once (as a Broker) where the Owner had forgotten that the Hot and Cold feeds had to be reversed for each side; but he left it like that for me to explain to prospective Buyers . . . . so that in the Vanity, HOT was on the right and COLD was left. That can be dangerous in an emergency. I can't see your feed lines, so just thought I'd relay this story while there may still be time !
 
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Old 04-10-18, 04:50 PM
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Originally Posted by Vermont View Post
Doing back-to-back bathrooms reminds me of a house I sold once (as a Broker) where the Owner had forgotten that the Hot and Cold feeds had to be reversed for each side; but he left it like that for me to explain to prospective Buyers . . . . so that in the Vanity, HOT was on the right and COLD was left. That can be dangerous in an emergency. I can't see your feed lines, so just thought I'd relay this story while there may still be time !
Yeah, the plumber told me something about making sure to reverse the lines. I don;t have them hooked up yet. Are the pipes in the top pic ok? You think I should bother cutting and add a Y pipe to the left to make one pipe?
 
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Old 04-10-18, 09:11 PM
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Apologies for the late reply. Your work looks good. The only thing that I would look to change is in this image.
https://www.doityourself.com/forum/a...mg_1217jpg.jpg
Where you have that first grey / blackish elbow that rolls up. That hole line should be roughly horizontal (slight grade uphill towards your trap (1/4"/foot)). When it rolls up this creates an s trap. This leaves your P trap beneath your sink unvented which runs the risk of sucking itself dry which can lead to sewer gas. It is a simply fix. It looks like the pipe comes off of the drain in the back from a Y on a 45* angle. I would cut it so it can keep running straight on that angle then turn with a single 45* corner towards your trap.
If not, you could always turn that 90* elbow that is facing up, on its side. Ideally you want that run to be horizontal without jumping up like it is. I'm not the best drawer but this is an isometric drawing of what I mean.
https://sketch.io/render/sk-50fd86f5...8ecb18982.jpeg
 
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Old 04-11-18, 03:02 AM
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Originally Posted by kellogs View Post
Apologies for the late reply. Your work looks good. The only thing that I would look to change is in this image.
https://www.doityourself.com/forum/a...mg_1217jpg.jpg
Where you have that first grey / blackish elbow that rolls up. That hole line should be roughly horizontal (slight grade uphill towards your trap (1/4"/foot)). When it rolls up this creates an s trap. This leaves your P trap beneath your sink unvented which runs the risk of sucking itself dry which can lead to sewer gas. It is a simply fix. It looks like the pipe comes off of the drain in the back from a Y on a 45* angle. I would cut it so it can keep running straight on that angle then turn with a single 45* corner towards your trap.
If not, you could always turn that 90* elbow that is facing up, on its side. Ideally you want that run to be horizontal without jumping up like it is. I'm not the best drawer but this is an isometric drawing of what I mean.
https://sketch.io/render/sk-50fd86f5...8ecb18982.jpeg
Could I branch out of the back pipe with a Y in the middle some where and connect the 2 pipes? I remember the plumber told me to cut AFTER the grayish pipe now!

I believe after that gray pipe that goes down on the right there is some sort of Y pipe, but that still leaves me with the redundant 2 pipes going horizontal ....

So I've got to eliminate that gray pipe going down on the right correct?

Why do they make S traps if they're so bad? Just curious.

Also the 1/4 per inch thing. Is that slope needed? I notice in a lot of commercial settings like at work in the office there's no slope and even sometimes slopes UPWARD slightly instead of downwards.

Since this drain is a little "wacky" I'm thinking of getting a clear P trap so I can always check that there's water in it!
 

Last edited by Brian1900; 04-11-18 at 03:34 AM.
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Old 04-11-18, 09:48 AM
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I would rework it a little and cut off that gray 90deg fitting. Something like this below.

You could wye into the vanity line, but then you're dealing with either replacing some working piping or using rubber couplers, and it's just more of a pain.

It looks like you're really close!
 
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Old 04-11-18, 01:14 PM
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How does this look? It's not GLUED in yet. WANTED to ask before I glue it together this time lol!

I got two 45 degree angles and a trap adapter and I'll glue them all together for the bend in the right there.

The trap adapter didn't come with an O ring, but it has sort of one BUILT IN it looks like. The pipe goes in fairly tight I'd say.

There was a Y already in the back and then a short section of PVC pipe which is where I made my cut so that it sticks into the new angle section that I just went out and got. Seems to fit together nice, but I have to file some ends and debur a little, etc.

Actually I'm going to install a CLEAR trap just so I can keep an eye on everything from time to time.
 
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Last edited by Brian1900; 04-11-18 at 02:01 PM.
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Old 04-12-18, 06:10 PM
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Looks perfect! I would tip the 90deg up a hair, so the horizontal section has a fall to it. Right now, it looks like it's back-pitched.

But otherwise - looks perfect!
 
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Old 04-12-18, 09:32 PM
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Looking good. Just as Zorfdt mentioned, you just need some grade and you'll be set. Great work.
 
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Old 04-12-18, 10:02 PM
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Here it is all together! Had a couple leaks, but just had to retighten the pipes a bit. New vanity installed on opposite side and new Delta faucet installed! Nest I'll be re-laminating the counter and tiling the floor in the small bathroom where the vanity is!

I decided to install a CLEAR P trap so I can occasionally see everything working! Oh and I'll be cleaning up under the sink and adding new shelves and maybe a little paint.
 
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Old 04-13-18, 12:05 PM
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Looks great! This is the first time I"ve seen a clear trap. I think I rather the white ones... I wouldn't want to see what's in there in a few years
 
 

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