Advise on removing washing machine drain pipe

I have a 1.5" galvanized steel washing machine drain pipe that ties into 60 year old cast iron pipes that goes to a new pvc drain pipe. There is a vent pipe that goes to the roof as can be seen in the photo.
. I'm not sure whether to get rid of all the cast iron and replace with pvc (or new cast iron) or do a partial replacement. I'm leaning towards getting rid of all the cast iron but leaving the metal vent pipe, it starts at 1.5" thick but transitions to 2" in the attic.....

I am thinking that the sizes you are stating are way off.
But maybe you are right. My eyes are old.

Meanwhile, you buried the lead, why do you want to eliminate the cast iron?

And what are those little skinny flex lines?

Those last two shots are the drain in a crawlspace?

Your biggest win, if it really needs replacing, is to replace the standpipe, trap, and the tee. Replacing any of the vent line isn't likely necessary, unless it's corroded enough and leaking.

If that PVC in your pics is the drain pipe, you can just rebuild from there, and cut the vent above that tee, slip a fernco on there to connect to the new PVC, and you'd be set. Get rid of that old fernco on the drain line, and convert sizes with a bushing.

If that is the only thing left in cast iron I would eliminate it. Can't tell if that's 3 or 4 " but around here you have to run the
3 or 4" pvc over to the wall and then run 2" up in the wall with your tee and trap and then tye on to the vent with a shielded
coupling.

Jeff Handy said:

I am thinking that the sizes you are stating are way off.
But maybe you are right. My eyes are old.

Meanwhile, you buried the lead, why do you want to eliminate the cast iron?

And what are those little skinny flex lines?

Click to expand...

The reason for getting rid of the cast iron is we hooked up a washing machine and the water from the machine back flowed out of the standing pipe into the laundry room.....the cast iron has been there over 50 years and as long as we're going to put a new 2" standing pipe thought we might as well go all the way and take out the iron.....it may be corroded, backup up with lint etc....also, there is 1.5" galvanized pipe going from the trap into the tee.....so t, trap probably all has to go... the skinny lines are for a reverse osmosis water system that is being run off the supply line.

Helper Dave said:

Those last two shots are the drain in a crawlspace?

Your biggest win, if it really needs replacing, is to replace the standpipe, trap, and the tee. Replacing any of the vent line isn't likely necessary, unless it's corroded enough and leaking.

If that PVC in your pics is the drain pipe, you can just rebuild from there, and cut the vent above that tee, slip a fernco on there to connect to the new PVC, and you'd be set. Get rid of that old fernco on the drain line, and convert sizes with a bushing.

Click to expand...

Yes the last two shots are in the crawl space immediately below the washer room. The vent line is without any corrosion and looks totally clean and isn't likely having any issues. Yes the PVC is a pretty new (4 years old) drain pipe.....So, cutting out all the iron, from the PVC to the vent pipe above the tee, and just replace with new PVC.....that sounds like the way to go......thanks....

TomFOhio said:

If that is the only thing left in cast iron I would eliminate it. Can't tell if that's 3 or 4 " but around here you have to run the
3 or 4" pvc over to the wall and then run 2" up in the wall with your tee and trap and then tye on to the vent with a shielded
coupling.

Click to expand...

Thanks, eliminating all the iron is what i'm going to do......Just wanted to see if anybody came up with a reason not to eliminate it all, and so far seems consensus is to get rid of the iron.

Helper Dave said:

Those last two shots are the drain in a crawlspace?

Your biggest win, if it really needs replacing, is to replace the standpipe, trap, and the tee. Replacing any of the vent line isn't likely necessary, unless it's corroded enough and leaking.

If that PVC in your pics is the drain pipe, you can just rebuild from there, and cut the vent above that tee, slip a fernco on there to connect to the new PVC, and you'd be set. Get rid of that old fernco on the drain line, and convert sizes with a bushing.

Click to expand...

A question. The tee in the pictures going to the vent pipe and to the drain pipe down to the crawlspace is coming in at a 90 degree angle, when the tee is replaced should it be coming in at an angle for easier drainage, using a Y connector or is it o.k. to use a 90 degree tee?

suntele said:

A question. The tee in the pictures going to the vent pipe and to the drain pipe down to the crawlspace is coming in at a 90 degree angle, when the tee is replaced should it be coming in at an angle for easier drainage, using a Y connector or is it o.k. to use a 90 degree tee?

Click to expand...

Also, that new 2" piping should tie into a 3" as soon as possible, to help accommodate the higher flow rates of the newer washing machines. At the tee would be good.
What size is your newer section of PVC?

Diehard said:

View attachment 23427
Also, that new 2" piping should tie into a 3" as soon as possible, to help accommodate the higher flow rates of the newer washing machines. At the tee would be good.
What size is your newer section of PVC?

Click to expand...

I just measured the new PVC, and it's about 4 inches measured from the outside. In the second picture it says "Y and 1/8th bend prohibited"......is the second picture of the prohibited Y or is the prohibited Y with the 1/8th bend something different? It appears the sani-tee is the right one.....or maybe some type of Y?

Edit : I looked more carefully at the pictures and the bottom one has the trap weir above the vent opening...so the sani-tee is what is needed.

the top pic is what is legal

The O.D. of 3" PVC is about 3.5"
The O.D. of 4" PVC is about 4.5"

So it sounds like it could very well be a 3".

Is that insulation on it?

Reduce it down to 2" as soon as you turn the 3" or 4" up in the wall.

When you do the repipei.install a dandy clean out on the vent at a height just above the washing machine if you have to snake its a direct route to the drain cut an access panel in the dheet rock and it will look neat/clean