Adding laundry sink

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Johnr981

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Hey all, I want to add a laundry sink to our utility room. I was planning on tapping into the existing plumbing for the washing machine. The utility room shares a wall with the garage so I went ahead and opened up the wall from the garage side to see what it all looked like. I found that the washing machine drain pipe has no trap visible (maybe below the slab?), and no vent. I hopped up in the attic and verified no vent pipes anywhere above the utility room. The house was built in 1987 and I am in the Dallas/Fort Worth area. My question is- what do I do to add the sink? I want to put the sink in the area denoted by the red box. Do I need to go ahead and add a vent and a trap to the existing washing machine drain pipe and then add the laundry sink plumbing to that? Are there any other foreseeable issues? Any and all comments are appreciated. Thank you!

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Johnr981

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Thanks Terry. Was this a common setup for just a washing machine in the late 1980s? Would it have passed code back then?
 

Johnr981

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No, that looked like an afterthought after the home was inspected. Nobody ever did them that way.
Interesting. Ok, well should I check to see if there is a trap under the slab before I add a one in the wall, or does that even matter? Thanks again.
 

wwhitney

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Yes, you have to check, you need exactly one trap, not 0 or two in a row. And since there's obviously no vent, you'll need to have the trap and vent above the floor.

That means if there's a buried trap, you're going to have to break concrete to remove that trap.

If there's no trap, you'll be fortunate on not having to break concrete, but I would also think you'd have been getting sewer smells since that was put in.

Cheers, Wayne
 

WorthFlorida

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The concrete floor looks that part of it was broken out and replaced more recently. With copper pipes and right next to it is a dryer duct, this had to be in place when the home was built. Code requires that the trap must be above the floor except for showers and tubs, but without a vent something is not right. Are you on city sewer or septic tank? As Wayne stated, you should have been smelling sewer gas if there is no trap below grade.

Was the floor broken up to fix a leak when you had the hard freeze two years ago?

This is setup is close to what you need to do, however, your washer box may need to be moved over to the left (picture side) to the next stud cavity to make room for a trap. A camera may be the only way to know if there is a trap or not.

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Johnr981

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Thanks again for the replies. I have never smelled any sewer gases, so based on what y’all are telling me there must be a trap for the washing machine below the slab. We have been in the house since 2018 and the floor was like that when we bought the house. We were told that there had been a leak in a copper pipe supplying the washing machine that had been fixed. And btw WorthFlorida, we are on city sewer.

So, sounds like if I want to add a sink then I definitely have to open up that patched hole and remove the washing machine trap under the slab. Just to clarify Wayne, is it a violation of code to just add additional traps for the washing machine and new sink above the one under the slab, or is it just bad mechanics that would lead to problems.
 

Terry

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It's hard to say if you would smell it or not if it was missing a trap. I was at a friends home, and I noticed a smell at the kitchen sink. There was no p-trap and it was sewer gas I was smelling. She thought that was a normal smell in the kitchen. It wasn't. I lowered the drain in the wall so that I could add a p-trap to the sink. Problem solved.

One trap works, two traps are a problem.

I doubt there is a trap there at all. They would have also installed a vent for a trap there. From my standpoint of dealing with handymen, there is no logic to them. They will argue until you want to punch them in the face, telling you that facts don't matter if they can convince their GF that they're right and everyone at work is wrong.

We have plumbing guides, rules, checks and inspectors. We kind of forced to do things right.
 

Johnr981

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Got it. I will verify if there is a trap before I do anything else, but I bet there is one under the slab. I did find out that my city adheres by the IRC. That being said, I am inferring that there would not have been a requirement in the IRC at the time the house was built to place the trap above the floor? If it turns out that there is indeed a trap below the slab, then would the clothes washer be considered legally vented if the clothes washer trap arm tied into a vent that is located in the kitchen or master bath nearby (is that what is referred to as a wet vent or common trap arm)? Anyway, if there is a trap under the slab below the clothes washer standpipe, then do the exceptions listed in IRC P3201.6 allow me to splice in a santee to the standpipe and just connect the laundry sink that way? Either way, I am going to get a local plumber to come by and look it over with me, but I still appreciate the additional expert opinions.
 
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