Venting Washing Machine - Has Running Trap

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Paul E.

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Howdy ya'll, happy New Year!

I am looking for advice on how to improve my current venting setup on a washing machine that is connected to a running trap.

This is your typical Texas slab on grade house and the slab has post-tensioned cables in it. The plan diagram below shows how the washing machine is connected to the kitchen sink waste line via a running trap. The kitchen sink is about 10' away from the washing machine.

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The previous homeowner rigged a 3/4" PVC vent that pokes out the exterior wall and vents to the backyard.
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I would like to add a vent up through the roof but am not sure how that can be done with the running trap. My understanding is that the vent should connect downstream of the trap to avoid siphoning concerns. Is there a way to add a vent to the roof in the current setup I have?
 

Jeff H Young

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its nothing I ever seen.
I don't know how you determined a running trap ? Crack slab where trap is remove running trap and plumb it American Style.
I'd probably leave the underground alone and plumb it American Style and add a p trap and vent its a hokey build my opinion but I wouldn't want to crack slab If its plastic underground and not just a total mess it should work . or abandon all that crap and dig around the garage outside no big deal
 

Reach4

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Most of Texas uses IPC, so AAVs can be used for vents.

"how the washing machine is connected to the kitchen sink waste line via a running trap."
connected how? before the trap U, or after?

I am wondering if that 3/4 was not intended as a vent, but as a pressure relief in case the path toward the kitchen got clogged.
 

wwhitney

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I am looking for advice on how to improve my current venting setup on a washing machine that is connected to a running trap.
What makes you think there is any sort of trap under the slab, vs just a drain without any trap?

If the latter is what you have, it's easy to do a proper plumbing install just by changing the above slab plumbing at the washing machine.

Cheers, Wayne
 

Jeff H Young

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What makes you think there is any sort of trap under the slab, vs just a drain without any trap?

If the latter is what you have, it's easy to do a proper plumbing install just by changing the above slab plumbing at the washing machine.

Cheers, Wayne
Thats what I would do plumb it normal above slab regardless whats below if it dosent work , bust out slab or run new line around house
 

Reach4

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Is there any symptom, other than looking squirrelly?
 

Paul E.

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Regarding the running trap, I had a camera inspection done by a local plumbing company, and they stated that there is a running trap between the washing machine and the sink. The plumber started fishing their camera from the washing machine drain and hit a point in the line where their camera was unable to continue on to the kitchen sink. They indicated this was a pretty common setup for houses built around that time—1969.

UPC is the plumbing code I am subject to in this part of Texas.
 

wwhitney

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The plumber started fishing their camera from the washing machine drain and hit a point in the line where their camera was unable to continue on to the kitchen sink. They indicated this was a pretty common setup for houses built around that time—1969.
Then ideally they would have given you a length to trap measurement, which would allow you to mark out on the floor where to break it up to remove the running trap. Then you could plumb the washer standpipe above the floor as the UPC requires.

Cheers, Wayne
 

Jeff H Young

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Regarding the running trap, I had a camera inspection done by a local plumbing company, and they stated that there is a running trap between the washing machine and the sink. The plumber started fishing their camera from the washing machine drain and hit a point in the line where their camera was unable to continue on to the kitchen sink. They indicated this was a pretty common setup for houses built around that time—1969.

UPC is the plumbing code I am subject to in this part of Texas.
Assuming it was legal or not it is what it is why are you working on it? If I was working on it I'd still do it as I recommended.
 

Paul E.

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I don't think they marked out where the trap fell on the concrete, I'll have to check as that could be really helpful information. The area does have several post-tensioned cables running across the drain line, so I won't crack into that slab lightly.

Over the weekend I replaced the other vent boots on my roof. This led me to look at this venting system and trying to evaluate if it would be better served by a through the roof vent. It looks pretty weird as is, I wasn't sure if it was OK or not.

Since I haven't hooked up a washing machine, I can't speak to how well the system works. I could run a garden hose to the drain line to try and simulate a washing machine, if that would be an accurate test?
 

Jeff H Young

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I don't think they marked out where the trap fell on the concrete, I'll have to check as that could be really helpful information. The area does have several post-tensioned cables running across the drain line, so I won't crack into that slab lightly.

Over the weekend I replaced the other vent boots on my roof. This led me to look at this venting system and trying to evaluate if it would be better served by a through the roof vent. It looks pretty weird as is, I wasn't sure if it was OK or not.

Since I haven't hooked up a washing machine, I can't speak to how well the system works. I could run a garden hose to the drain line to try and simulate a washing machine, if that would be an accurate test?
I dont know if there is a need to bust floor If you arent getting stoppages or some bad effects. or really to do anything , But Id want a vent through roof and be certain you are protected by a trap . to really be satisfied.
I dont want you to get into a huge job if its draining ok
 

Paul E.

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I was able to wrestle the cast iron pipe out to get a better look at what is happening at the slab. There's a 2" cast iron hub that transitions to an 1-1/2" I.D. pipe. Shouldn't a washing machine be served by a 2" drain line?

I'll run a 36" long borescope down the line to see if I can locate the running trap.

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Jeff H Young

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Im not re reading anything you wrote , but a laundry should be 2 inch if you can. not saying you tear a house down to replace a undersized pipe though.
 

Paul E.

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Turns out the running trap was connected to the wye and eighth bend combo that serves the sink. You can see the combo turning up in this image, immediately after the running trap.
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I was able to get it out, eventually.
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Here's the end of the combo hub, downstream of the running trap. I'm going to try and clean all that junk out, and avoid pushing it farther downstream.
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Upstream of the running trap. This line connects to the washing machine. There's an odd amount of buildup on the sidewall of the pipe.
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What are my options for a below grade horizontal connection, that will connect a new 2" PVC line to the hub of the cast iron combo?
1. Can you use a donut underground for a horizontal connection? That seems like the simplest way to transition to PVC. I've been using a Fernco 22U-205 elsewhere, but that's been for a vertical connection above the slab.
2. Would a flexible coupling be appropriate? The Fernco 1056-22 states that it is for use above ground. Seems like I'd need to cut the hub off the combo, or add a short run of cast iron into the combo, and then attach to that.

I appreciate all the help ya'll!
 

Jeff H Young

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Sure use the donut (easy and just as good ) or the other way you mentioned. looks like the problem was a stoppage, I didnt expect a running trap but see you were correct. so hook up the plastic and run it like any other modern was machine with vent out roof or AAV if you want
 
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