Should I route the pipe inside or outside?

I need to route a 3" PVC drain pipe from my garage (from the washer) to the kitchen drain.
There is an interior wall separating the kictchen and garage. The washer is sitting against this interior wall about six feet from the exterior block wall. The kitchen sink is against the block wall on the other side about another 4 feet from the interior wall. So from the washer to the kitchen sink you have to route the drain along the interior wall, then make a turn to connect to the kitchen drain.
My question is, should I do the routing from the inside or outside?
Inside: Run the drain from the washer inside the interior wall. When we reach the exterior wall, make a 90 degree turn and go through the interior wall. The other side is the kitchen cabinet. Drill through the kitchen cabinet divider and reach the sink bottom, then open up the wall from the inside, and connect to it.
Outside: Run the drain from the washer inside the interior wall. When we reach the exterior wall, drill a hole in the concrete block wall so the pipe can run through. Next locate where the kitchen drain is in that wall, knock it open. Once you see where it is, break the exterior wall from the outside and notch a trench that will take you from there to the kitchen drain. Connect the pipes up inside the block wall, then cover it back up with concrete, apply stucco and repaint the outside.
Which way is better? How do one drill a three inch diameter hole through a conrete block wall? How easy is it to chisel out a trench along the wall to seat a 3" pipe completely inside? I think that would be a lot of work? I think routing the pipe completely out and back in will be real bad right?
O
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orangetrader wrote:

Perhaps you would like to suggest where you live. In southern Ireland running it outside should not be a problem, in Alaska US it is not going to be a good idea.
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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Hold on there... A 3-inch drain just for a washer? Why so huge? Half that size is typical.
Also, a block wall is only 6" thick. A 3" pipe buried inside would require a 4" deep cut, at least, which would pretty much destroy the integrity of the entire wall. And that wall could easily be load bearing, too.
I'd just route a 1-1/2" pipe using your "inside" idea. Your washer hose might not fit in the pipe, in which case just add a 2" diameter stub on the end, with a reducer fitting.
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The block wall is 8" thick. I am located in Miami Florida so freezing is not an issue.
About load bearing, yes that is a good point.
O

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orangetrader wrote:

Why 3"? 1-1/2 or 2 (max) would be more typical for a washer.
My first question is about the relative heights...can you get enough drop to go 6' to an elbow and then another 4' to the down stack? There's going to be a problem perhaps in getting good flow. Also, what about trap and the vent?
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I never had to modify my washer drain pipe. I think it's galvanized steel, 2". I was flabbergasted once, years ago, to have a serious blockage. I had a flood in my washing room because of it. It seems the detergent I was using had caked the inside of the pipe, though I can't be sure. The problem disappeared as mysteriously as it appeared. I had tried to flush the drain with a hose, but that didn't work very well. What a mess that was. I have long since changed to a different detergent. The problem never came back. A washing machine pumps a LOT of waste water in a short time.

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John B wrote:

I'm not sure of your intended point, but yes, the pump discharge is pretty fast, but it's nowhere near a 3" pipe full...
But, if OP doesn't have enough (or any) slope and vent, he's asking for trouble even if he runs a 3" drain line...
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Point taken. Sometimes it makes sense to build or plumb in excess of code specifications. Case in point, using "L" copper where "M" is permissible. I like the drain pipe exterior, if "permissible." Why wouldn't it be permissible?

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It would be nice for your readers if you'd post a picture somewhere. Your description is inadequate, yet overly wordy. Why don't you just say the washer is in the kitchen? I see washers in garages, against interior walls. "Inside the interior wall" could mean inside the garage.. If it is not in the garage, why don't you put it there? Who would want a washing maching in his or her kitchen? Or is that a DISH washer? My vote would be to put it in the garage, with piping exterior, as long as code allows it. Aesthetics are of minimal concern in a garage.

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Sorry for not being accurate in my description. The washer IS in the garage. I am trying to drain the washer discharge to the kitchen sink drain because the drain line in the garage is "blocked".
O

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Thank you for the reply. I'm still not interested in deciphering those plumbing scenarios you painted. Why don' t you just get a professional to unblock the existing drain line, if you can't do it yourself? In the garage, this should be easy. I had unplug the washer drain pipe in my in-house washroom once, and that was a mess. It flooded repeatedly.

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I have already explored the suggestion you posted. To fix the crack in the drain pipe that is currently located about 12 inches beyond the 8" thick monolithic slab will require opening a hole on the kitchen side, ripping out the kitchen cabinets for access, and ripping out tiles that has no replacement. There is no access from the garage side because there is a intermediate concrete footing that runs along the separation wall between the kitchen and garage. Alternative 2 is to have someone dig a tunnel 6 feet long from the side under the house to fix it, either way the cost is extremely high and has other side impact that may exceed the inconvenience of the original problem. The soil is sandy. When the washer discharges the water pull sand through the crack and pile sand downstream in the main line which causes occasionally blockage. Right now my remedy is to pay $1000 a year to clear that blockage by reverse jet sweeping.

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Wow. When something is "cast in concrete," it is very hard to undo. Conversely, I rationalize horrendous challenges and accomplishments to "pride of ownership." It's kind of like the devotion a person might show to a sick loved one. No effort is too great.

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Yes.
Dimitri
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OK.

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