Ask Me Help Desk - Splicing into combo cast irion/galvinized pipe

My objective is to relocate the basement washer and utility sink to the wall in front of an existing wet stack and tap into the stack for drainage in my NJ home. I have 2 questions: is there a minimum height requirement from the floor to the bottom of the standpipe’s P-trap, and what is the best way to splice PVC to galvanized steel pipe (the washer and utility sink will have individual AAV’s) for drainage?

I’ve attached a picture of the 4” cast-iron waste line as viewed from the basement. This waste line services the 1st floor bathroom group (toilet, sink and tub w/o shower). The waste line exits the framing at the roof of the single story addition, travels up the side of the outside of the house, then terminates past the roofline.

Measurements in the picture were taken from the floor/top of a pipe hub to the top of the next hub. From the bottom up you have the 4” cast iron pipe entering the basement floor, a cleanout plug, and a wye connecting to 2” threaded pipe. The threaded pipe goes into the addition’s crawlspace, where it branches into drain lines for the sink and tub. Continuing upward along the vertical cast iron is a tee connection which goes into the same crawlspace and connects to the 1st floor toilet.

My thoughts are to leave about 2” of visible cast iron sticking out of the basement floor, then use a banded coupling to switch to PVC. After installing about 2” of visible pipe I assume I have to have a cleanout, which would be followed by a wye with a 2” connection on the left hand side to accommodate drainage for the utility sink and washer standpipe (LHS connection would be followed by a 45 degree elbow, 2” visible pipe as a spacer, 2” wye with a 1 ½” inlet, inlet facing upward, plumb inlet to utility sink, plumb 2” side of wye to standpipe.

On the main stack I would continue with another 2” of visible pipe above the washer/standpipe wye for spacing, followed by a right hand side wye with a 2” inlet to accommodate the 1st floor sink/bathtub. Because I moved up the point where the sink/bathtub hits the vertical drain, I should need a longer horizontal run. Should I use another banding coupling to connect PVC to the 6.75” horizontal length galvanized steel, or is there another product which is better suited for this purpose?

I can't answer for your local codes, but your thought process sounds pretty good.

I would cut the cast as high as I could above the concrete, say 4" in case anything goes wrong. Even better, dig out the caulking and use a rubber bushing inside that hub to adapt to the PVC. If a 4x4x2 street wye will allow the line to be low enough for your sink trap hub, that method would be the best. I don't think you will need 2 AAVs, just one at the end of the line.

Keep in mind that you will need to support the remaining cast iron pipes. In other words don't cut so high that there's nothing left to get support under or around. I would go above the crawlspace tee if there is plastic out there. If not, then support the cast tee, dig out the caulking and remove the 37" piece of pipe, and use a Fernco or banded coupling on the spigot end.

As to your 2" steel line, I would probably cut on the 3" side of the cleanout tee and adapt there with a Fernco or whatever is required. Then I would replace that steel tee cleanout with a PVC wye cleanout. I also would check the condition of the rest of that 2" steel line. It might pay you to replace back farther in the line while you are doing things. Steel pipe really gets rough inside and you don't want to come back 3 years from now and replace it. You also have to support that steel line correctly.

EPM

EPM gave you good answer...

In addition: Here is an easier approach. You can unscrew that 4" Clean Out plug out, screw in PVC male adapter, glue into this adapter 4x2 PVC bushing, and run your 2" pipe for washer as you wish.

This way - there is no cutting and support problem. It can be done in 15 minutes.

In my area, we are required by the Code to have bottom of the P-trap at 6" from the floor. Stand pipe should be 30" high. All washer plumbing is in 2".

PS: You offered an excellent visual to support your question. The best post I have seen in this forum so far...

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In my area, we are required by the Code to have bottom of the P-trap at 6" from the floor. Stand pipe should be 30" high. All washer plumbing is in 2".

Which is just another stupid UPC. Common sense dictates that the trap be as close to the floor as it will go and the stand pipe should be a minium of 3 feet. We both agree to a minium of 2" for the drain but in my area if the kitchen and washer's on the same branch we go to 3". Growler couldn't explain why traps should be 6" off the floor. Perhaps Milo can shed some light on this. Outside of being hung up on nutty codes Milo gave you the best and easiest way to tie the slop sink and washer station back to drainage.

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Here is an easier approach. You can unscrew that 4" Clean Out plug out, screw in PVC female adapter, glue into this adapter 4x2 PVC bushing, and run your 2" pipe for washer as you wish.

You may come off the bushing to pick up the washer and connect the sinks trap back into the washer vent pipe, (you were going to vent these weren't you?) where it will will wet vent the washer. Another way would be to come off the bushing with a wye and pick up both traps that way. You would need to vent each of them separately but tie them back together to make one vent pipe that either goes out the roof or revents back into a existing dry vent. Good luck, Tom