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Discussion Starter #1
Let me preface this with saying, I'm handy... but haven't ever done any plumbing aside from simply replacing a leaky pipe/faucet. So please be patient with me.

Also, I'm in Los Angeles California, just in case someone is local and knows any specifics.

I have a 4" cast iron Y where the 4" goes to a toilet and the 2" goes to my kitchen sink and washing machine (my house is old and it's a very slow drain). The Y is slowly leeching waste through parts of the cast iron.

I'm remodelling the kitchen and laundry room. there will be a dishwasher that gets added. there's about a 9 or 10 foot run between the Y and the wall where the appliances will be.

My current plan is:

1. Cut the Y just below where it splits
2. Join new 4 inch ABS Y (where both ports are 4") with one of those rubber couplers (don't know the name)
A. Top 4" will go to the toilet as before
B. Split 2nd 4" into 2 2" lines
3. Run the 2" lines to the wall/appliances with the angle at 1/4" per foot until they go vertical.

Does that seem about right? What changes should I make?

I have a question about venting:

Washer/sink/dishwasher will be on an exterior wall. I was thinking it would just be much easier for me to run an exterior vent then to try and tie into the other ones. How high am I required to run the vent for plumbing? For some reason I have a number of 18" above where it exits the roof stuck in my mind, but can't remember where I saw that.

Also, what diameter pipe should the vent be to accomodate those appliances?

thank you for your advice, I really appreciate it
 

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i would use a 4x3 wye. 3 inch is plenty for a sink and washer. is there an existing vent? 2 inch would be plenty big enough for the vent. we used to expose the pipe 10-12 inches on the high side when we went through the roof. how far apart are the washer and sink? if they are in the same area just run 3 inch over and split it there.
 

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Discussion Starter #3
The existing vent is back near the CI wye (roughly 12 feet), which is in the middle of the house.

Also, the house was built in 1905 and the vent is steel (I'm assuming). I wasn't crazy about tapping into it because everything in the house drains extremely slow as-is. Also, even after gutting my kitchen I could barely see the top of it. I'd have to rip out a whole separate wall to have real access to it :(

I figured I could put the kitchen, laundry, and downstairs bath (which are in the same area of the house) on one new vent. Then when I redid the other two baths, I could put those on a new separate vent. Hopefully the two vents will solve my problems.

Thanks for the advice about running one pipe and splitting in at the end. I really should've thought of that one.

The sink, dishwasher, and washing machine will be along the outside wall. It would be easy for me to merge them into one vent.

I had one more question....

I haven't researched it yet, but where should I add a cleanout?
Would it be where the 3 inch would split to the kitchen and laundry?
That would be at an exterior wall, and very easy to create a port that someone could access from outside. In my mind that makes sense.

Again, I'm not a plumber and very humble and new to drain lines.

Thanks again for your help
 

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I believe LA code is very similar to what I work with in Idaho. Here's how we would size your fixtures-
Pipe sizes for drainage are based on drainage fixture unit ratings(DFU). You can put a kitchen sink w/dishwasher and washing machine on a 2" pipe, either horizontal or vertical (UPC). However, a minimum 2" pipe is mandatory for a sink. A 1.5" vent will handle each individually or combined and should terminate at least 6" above the roof. A kitchen sink requires a cleanout at it upper terminal- usually inside the cabinet.
When cutting into the 4" CI pipe I'd suggest removing as much as possible. If the wye is failing so is the pipe. Support the pipe well before cutting it- its very heavy.
Consider having your 4" line scoped with a camera. If the whole system drains slow, you may have an issue between the house and the city sewer.
 

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Discussion Starter #5
Thank you!

That helps tremendously.

I have a question about this:
"A kitchen sink requires a cleanout at it upper terminal- usually inside the cabinet."

I'm assuming that refers to the opening I usually see in the bottom of kitchen sink traps.... if you are referring to something different please correct me.

In preparation for this, last week I did have a company come out and scope my main sewer line. The only cleanout I could find was behind my guest house at the very back of my property. He said the line was in good shape. I'm guessing it was replaced at some point because a slice of my driveway was obviously cut and replaced before I bought the home.

Anyways.... it's a long run from the back of my yard to the street (I paid a lot of $ for that scoping). That's why I was hoping to add a cleanout to the 3" line I'm about to add.

Would it be ok for me to add a cleanout to the new 3" line that is accessible from the exterior of the house? Or, will the access at the drain of the kitchen sink be all that I need for all roto rooting I may require in the future?

Thanks again
 

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In LA you might do something like this with your sink clean out. Its not built into the trap. Its installed in the vertical drain pipe. Up here we put it inside the cabinet-not outside.
The clean out for the main line should be the same size as the main itself. If smaller, you cannot get large enough cable blades into the line to clean the larger pipe- 4" knives will not fit into a 2" pipe.
Hope this helps.
 

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