Replacing 1 1/2 galvanized wash machine drain pipe

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sparkync

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My wash machine is located on a cement slab in my house. It actually used to be a garage before I bought the house and a previous owner closed it in and made a den and a laundry room out of it. My problem now is that the washer drain is not big enough to take care of the water from our new washer(it overflowes). In the crawl space I can see under the slab somewhat. I can see where the galvanized comes through the floor ( there is somewhat of a small space where the dirt has evidently settled through the years). This may be a plus in me trying to replace it with 2" pvc. They have the galvanized going through the slab into a trap under the slab. The roof vent is coming out of this vent back up through the slab, then 90's through the wall, then 90's again up through the roof. Under the house the drain then comes approximately 5 ft. before it reaches the crawl space, then slants its way down the wall, makes another 90, then goes under ground to a separate drain tank under ground. My idea of replacing it is to bust the concrete around the existing galvanized, cut the vent pipe that is coming back up through the slab, and remove the galvanized from under the slab, by cutting it under the house and removing the rest of the galvanized where it goes under the ground. I would then install a surface mount wash machine drain box behind the washer location, somehow either tie the 1 1/2" galvanized vent back in to the drain box, or try to run another pvc vent up through the roof. Then run my new 2" pvc drain down from the new drain box into a "trap" then try to somehow get it under the slab through the small area that is open under the slab, then make my way back to tie it in where it goes under the ground.
If you can visualize what I'm trying to do, I would appreciate your input as to if I've got the right idea or not. Another concern I have is, that when I start busting the concrete out around the existing galvanized, that it don't start cracking the rest of the slab that is undermined under it. A small hallway also goes across this slab before it is terminated to the crawl space. Any better idea is appreciated. This will be a major project for me, and I would call a plumbing contractor, but cannot afford it right now. My wife is having to pack towels around the drain right now to try to minimize the amount of water that is draining into the floor. Thanks a lot for your input.
 

Cacher_Chick

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The big question would be what exactly is the final connection beyond the new 2" line? You will need to tie into the main drainage pipe for the house, which is likely to be a 4" cast iron line.

The trap and vent connection should be above the floor and the vent cannot go horizontal until it is at least 6" over the top of the washer basin.

Stealing Terry's picture-
washer_rough_b.jpg


You will need to remove whatever concrete is necessary to fill all the open space below it with sand/gravel before replacing the concrete.
 
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sparkync

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Thank you so much for the picture and description. The old saying " a picture is worth more than a thousand words" is so true, especially in an electrician's eyes with not much experience in plumbing. I hope you don't hold that against me:) I may start to tackle this project this week. I don't know how long it may take me. The wife may have to make some trips to the laundry.
PS. I just had a thought. Why couldn't I just saw the existing galvanized off at the floor, and use the old drain as sort of a "floor drain", and just run my new 2" like you've shown it in the picture ( I will have to run it surface mounted). That will put it a little closer to the crawl space for me. I may only have to bore a hole through the concrete for my 2", which I may
be able to work with. That will put it approx. 3ft. from the crawl space instead of 6 ft. I could then run my new 2" beside the old 1 1/2" galvanized under the house until it hooks into the sewer drain. Is there a fitting that will allow me to tie both pipes into the sewer drain?? If I do this, I could actually leave the old drain in place so my wife can at least still do some washing ( with the overflow of course), until I get to the place where I have to tie it into the sewer drain, which could feasibly be weeks for me:( Thanks Steve....

washer_rough_1.jpg
 
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sparkync

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Another question: Does it matter if the top of the new 2" drain is above the washer or not? Another plumber I had in the past raised my old 1 1/2" drain up above the washer trying to get it to drain better. I wouldn't think it would have to be on a new 2" drain since all the new installations I've seen are not. Thanks for the comments. Also I would think there needs to be a certain drop in the pipe ( out of level) to assure that it will run down hill. Thanks again...Steve
 

Cacher_Chick

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Standard height for a washer box here is 42" off the floor. The washer trap must have a vent. Horizontal pipe should be pitched at 1/4" per foot. A wye fitting is used to connect the branch to the main.

Floor drains are 2" or larger, require a trap in the floor, and in some locations a vent.
 

sparkync

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I got my hole through the cement slab. I used a rotary hammer and drilled about 8 holes to form a rectangle, then chiesled it out. I went under the house and had to knock 1 cement block out and some brick and gained access to the area under the slab after a little working back and forth I got my 2" pipe stubbed up through the concrete and tied into my washer box. I still have to finish tying it in under the house. After doing all this I ask the question: Surely it don't have to be black drain pipe!! I hope not. I didn't see any at the HD store. Please tell me it doesn't matter and that it is just that the brand is different that is in the picture above...I hate not being 100% sure of something. Maybe before I get too old I learn a little something about plumbing:) Thanks again... Steve
 

Cacher_Chick

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It's really more about local codes and what is approved for use. Black pipe is ABS, white is PVC. ABS is common in some areas and not in others.
 
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