Hi,
We recently finished our basement and added a laundry room with an eliminator box. The washing machine's 1.5 inch standpipe drops about 28 inches to the p trap and then connects to a horizontal PVC pipe that after about 48 inches rises 27 inches and connects to the wastewater pipe that drains the upstairs kitchen sink (old copper pipe). The horizontal PVC also carries the wastewater for the downstairs bathroom sink. Occasionally, and now maybe more frequently and more intensely, we get a sewer smell that seems to be coming out of the washing machine standpipe. As I understand, the likely culprits are either 1) the washing machine p trap is being siphoned or 2) the sewer stack is plugged. Since the sink (and every other fixture in the house) shares the same wastewater pipes, would it be likely that the sewer stack is plugged if the smell is only coming from the washing machine standpipe? The question is because if it is the washing machine standpipe is inadequate, the contractor that plumbed the laundry room will have to fix it but if it's likely the sewer stack I'll just get a plumber out to snake the stack. Does this make sense? Am I missing anything?

Thanks for any help you can give,
M

Is that washer drain vented ? How long is that horizontal 1 1/2" washer drain before it connects to the common drain ?

Yes, the washer drain should be 2" in diameter - but in many cases, 1 1/2 works just fine. Unless it oveflows, I would leave it the way it is...

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Originally Posted by Milo Dolezal

Is that washer drain vented ? How long is that horizontal 1 1/2" washer drain before it connects to the common drain ?

Yes, the washer drain should be 2" in diameter - but in many cases, 1 1/2 works just fine. Unless it oveflows, I would leave it the way it is...

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Thanks for the fast response. The washer drain is only vented after the common drain (via the sew stack). The horizontal section from the p trap is about 36 to 48" long, then it rises vertically about 27" to meet the common drain.

Thanks,
M

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Originally Posted by Milo Dolezal

Is that washer drain vented ? How long is that horizontal 1 1/2" washer drain before it connects to the common drain ?

Yes, the washer drain should be 2" in diameter - but in many cases, 1 1/2 works just fine. Unless it oveflows, I would leave it the way it is...

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Included a diagram... hope this helps!

Is this Side View? Why are you going 27" UP ??

I really hope I am picturing your rough-in incorrectly. Please, confirm. If it is correct than the 27" rise is incorrect, if not strange, installation. Also, I don't see any vents. That 1 1/2" pipe is draining 2 fixtures: w/m and sink. Therefore, it is undersized.

First: See my drawing. Can you connect it the way I drew it ?

Milo's bang on!
That 27" raiser double traps the washer right along with your upstairs bathroom fixtures. Get rid of it and follow Milos layout. Good luck, Tom

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Originally Posted by Milo Dolezal

Is this Side View ?? Why are you going 27" UP ??

I really hope I am picturing your rough-in incorrectly. Please, confirm. If it is correct than the 27" rise is incorrect, if not strange, installation. Also, I don't see any vents. That 1 1/2" pipe is draining 2 fixtures: w/m and sink. Therefore, it is undersized.

First: See my drawing. Can you connect it the way I drew it ?

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The connection to the common drain really does go back up. No idea why he connected it like this. Looking at it now, I suppose I would have thought that big vertical change to the common drain would have acted like a big trap but I noticed today that the sewer smell is is actually blowing out of it (you can feel a breeze on your hand) so it can't possibly be holding water in the horizontal connection. I also tried pouring a couple of gallons of water down the standpipe but that didn't stop the sewer smell coming out.

Thanks,
M

Somehow I think this more like what Emdub is trying to show. Washer stand is draining through bath sink drain. Vertical pipe is intended to be vent, just to far away from trap.


Emdub.
Pour a pint, no more, of water in washer stand to see if that stops odor.

Milo, Herald,
Wouldn't the lavatory be wet venting the washer? Regards, Tom

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Originally Posted by speedball1

Milo, Herald,
Wouldn't the lavatory be wet venting the washer? Regards, Tom

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I think I must be missing a part of the puzzle behind the drywall. There is a toilet in the adjacent room. The horizontal pipe must drain into the sewer at the point of the toilet and the vertical pipe back to the common drain must be there to vent. Otherwise, the toilet would have no vent and the washer waste water would end up in the bathroom sink (since it is the lowest point open to air). The laundry room also tends to get smelly if the downstairs toilet is plugged so I think this would make sense.


As an experiment, I plugged the standpipe. The smell was a bit reduced but seemed to come up from the floor - presumably from the spot that there used to be a floor drain but the contractor put a wall over it since "it was no longer needed". Is this all just a dried up floow trap with a wall over it? I suppose that doesn't explain why the smell would come up the standpipe though...

Any thoughts? Thanks for the discussion so far - very helpful!

Cheers,
M

Bingo.. That old floor drain is most likely the source of smell. Water inside the trap has dried out and now it allows sewer gas in. It has to be plugged / sealed. Othewise, you have open sewer and sewer gas are venting into living space.
You can buy plug and plug the drain or push in old newspaper and pour at least 3" of concrete over it.

Now that drain/ vent diagram is still puzzling me. Are you sure that horizontal pipe doesn't go downward to the floor ? It must be so. The pipe going upward must be a vent.

Look one more time. Try to find out where it connects. Hint: Drains don't go UP but downward from fixture.

OK Guys,
I can see how this could happen. Follow me here!
The pipe up to the lavatory isn't vented. The washer discharges and starts the water down to the trap across to the ell and back up into some sort of a "common drain" that doesn't sound like a vent either. So now the washer pump's doing its thing and water's flowing down into this "common drain". Everything's draining just peachy keen and now the pump shuts down. But the water's still flowing down into this "common drain".
Can you say siphon? That's right Sports Fans! The water falling down the "common drain" is pulloing water right out of the trap leaving nothing but sewer gas behind.
I see drains, I see stacks, what I don't seem is vents. What's draining into the stack?
What's draining into this "common drain"? If this abortion had even been wet vented by the upstairs lav it would have broken the siphon but it wasn't.
That would explain the air in the pipes and the bad smell. Even if you find a way to vent this contraption you will still have setting water in the trap you have built.

My advice? Since looking at this piece of your drainage I believe you might have major code problms in the rest of your house. It's for sure you have one here.
If anybody can come up with a better explanation, I'm listening. Good luck, Tom

I would love to get an actuall look at this. Can you please post a few pictures of your setup. I just find it hard to believe that the drawings I'm seeing are correct. THe drain should not go up at all, let alone 27 inches. Also, you say standpipe is 28 inches high, so if the drain went up 27 inches, the standpipe would be full of water up to within an inch of the top of the standpipe. I suggest getting the plumber back to explain to you how they ran your waste and vent pipes. Also, see if they did indeed plug the floor drain before covering it, it they didn't, it is a very likely cause the sewer smell. You also said you can actually feel air coming out of the standpipe, this isn't good. I think we all would really appreciate a few pictures if you get time. Lee.

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Originally Posted by Emdub

the contractor that plumbed the laundry room
M

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One more question, was the contractor a licensed plumber, or just a general constractor. If he was not a licensed plumber, I suggest you get a LICESNED plumber into look at this mess. Please let us know the plumbers reaction when he sees this. You may want to make sure there are no small children in the area, as he may start to cuss uncontrolably.

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you say standpipe is 28 inches high, so if the drain went up 27 inches, the standpipe would be full of water up to within an inch of the top of the standpipe

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That's what I thought Lee until he mentioned the air left in the pipes. Think about it! The only way this could happen is if the water was being pulled out by a siphon.
If that configuration is as depicted there just isn't any other explanation. Regards Tom

I agree Tom. Good call. I still think this thing need to be looked at by a pro, or we need some pics to help us help them. This could be a bit of a job getting this all straightened out. Most likely will require cutting into wall and seeing what's there. Lee.

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Originally Posted by mygirlsdad77

I would love to get an actuall look at this. Can you please post a few pictures of your setup. I just find it hard to beleive that the drawings im seeing are correct. THe drain should not go up at all, let alone 27 inches. Also, you say standpipe is 28 inches high, so if the drain went up 27 inches, the standpipe would be full of water up to within an inch of the top of the standpipe. I suggest getting the plumber back to explain to you how they ran your waste and vent pipes. Also, see if they did indeed plug the floor drain before covering it, it they didnt, it is a very likely cause the sewer smell. You also said you can actually feel air coming out of the standpipe, this isnt good. I think we all would really appreciate a few pictures if you get time. Lee.



One more question,, was the contractor a licensed plumber, or just a general constractor. If he was not a licensed plumber, i suggest you get a LICESNED plumber into look at this mess. Please let us know the plumbers reaction when he sees this. You may want to make sure there are no small children in the area, as he may start to cuss uncontrolably.

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Ok, updated diagram attached. The angles in the room won't allow me to take a very coherent picture but the diagram is based on now getting a solid look at all but one part of the plumbing. One thing I am going off memory of is that he actually did install the P-trap with the standpipe. If he didn't it still wouldn't explain the smell coming out of the floor.

What I can't figure out is whether we have two problems or just one. The smell (and a stiff breeze) definitely comes out of the standpipe originally (problem number 1) but when I plugged the standpipe the smell seemed to come out of the covered floor drain (problem number 2). It seems to me that if the trap for the floor drain dried out, we would just have problem number 2 and no issue with the standpipe. Similarly, if we only had a problem with smell coming up the standpipe, plugging it shouldn't result in the smell being redirected through the floor drain. Make sense?

The contractor was definitely not a licensed plumber - excuses, excuses but we had a baby a couple of months early and needed to get the basement finished pronto. We weren't as diligent in making sure the last couple of weeks of the project were up to snuff. It seems to be biting us in the butt now.

Thanks again for everyone's help,
M

I would break out the cement covering the floor drain and fill the trap with cooking oit. Then cement it back up again. Then have the washer hookup installed correctly.
I've explained how this could happen in detail. Now it's your turn to answer my earlier question.

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I see drains, I see stacks, what I don't seem is vents. What's draining into the stack? What's draining into this "common drain"?

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Let us know more about your system. Regards, tom

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Originally Posted by speedball1

I would break out the cement covering the floor drain and fill the trap with cooking oit. Then cement it back up again. Then have the washer hookup installed correctly.
I've explained how this could happen in detail. Now it's your turn to answer my earlier question.
Let us know more about your system. Regards, tom

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I wish I had a better answer for this but I can't really figure out the venting myself. The house is from the early '50s and all the original plumbing was within a couple feet of the sewer stack. The newer plumbing in the basement is also all within about 5 feet of the stack although the actual pipe lengths are longer due to the vertical sections. I've attached photos with a corresponding labeled diagram to help orientate to them. I hope this makes sense!

I would disconnect"B" and "C" and cap the connection to "D". I would then lower "A" down and connect to "E". I would increase the height of the stand pipe to 36".
This would prevent the siphon from happening every time the washer discharges.
Good luck, Tom