Kitchen Drain 2 inch vs 1 1/2 inch

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Old 03-18-13, 03:20 PM
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Kitchen Drain 2 inch vs 1 1/2 inch

We currently have a kitchen sink with disposal with ! 1/2 inch drain. We do not have any issues with the drain (lived here 5 years, no problem) but are may be pulling out cabinets to get new ones and are thinking about replacing old cast iron 1 1/2 inch pipes while have access to them. If so should we upgrade to 2 inches? I have heard that water moves slower in them so they clog more, but at the same time I have heard they are wider so they are harder to clog.

The drain is for the kitchen only... no other fixture other than the sink with the dishwasher. All other sinks, tubs, etc go other places. Also, it is vented with a
1 1/2 inch vent.

Any insight?

Thank you!!
 
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Old 03-18-13, 03:25 PM
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Too big of a pipe and the water does not swirl properly. Which keeps the pipe clear.

Is this all vertical or horizontal?
 
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Old 03-18-13, 03:40 PM
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Lawrosa, thanks for fast reply.

After leaving the wall the drain pipe goes back under the sink/floor horizontally (with a slight slope) for about two feet then turns 90 degrees and goes about 5 feet horizontally until it reaches the main drain (i think they call it a stack) and meets up with the other pipes. So I guess it goes about 7 feet almost all horizontally with one turn until it reaches the main drain. I hope this makes sense. Thanks.
 
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Old 03-18-13, 04:07 PM
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What and where are you going to replace? Are you going to cut the stack to replace that 3x3x1 1/2 tee?

Cant go 2" into 1 1/2"
 
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Old 03-18-13, 07:12 PM
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I think I see what you mean,... . if we replace the 1 1/2 drain line with a 2 inch drain link then at the stack it will still have a 1 1/2 inch "stub" coming out of it and can't go from from 2 to 1 1/2 inches there or it may clog. I would have to have a plumber cut into the stack and replace the "tee" accomodate a 2 inch line... Is that correct?

Sounds like it is getting expensive now, so may just stay with the metal pipe we have now, but if we decide to invest into it, would it be wise to install the 2 PVC or a 1 1/2 inch PVC. (We figure better to get it out now since our house is 70 years old and leaks/clogs could start becoming a nuisance anytime now. Like I said, I have read some places that 2 inch is better and other places that 1 1/2 inches are better. Either way, I'll contact local plumber and see what he/she says and get prices.
 
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Old 03-18-13, 07:23 PM
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would have to have a plumber cut into the stack and replace the "tee" accomodate a 2 inch line... Is that correct?

yes

Install 1 1/2 as far as you can IMO. Snake whatever section of metal pipe is left....
 
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Old 03-19-13, 10:30 AM
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You might be over-thinking this. 2" pipe is required for some fixtures (shower, laundry), but there are reasons it's required there. Changing over your kitchen sink to 2" pipe won't get you anything that a new 1.5" pipe will.

If it were me, I would change the iron (likely galvanized steel) to PVC so you don't have to worry about it clogging over time. Leave the stack as-is and connect the PVC to the existing 1.5" pipe as close to the stack as you can get (6-12").
 
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Old 03-20-13, 04:16 AM
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Thank you for your reply. I definitely do tend to over think things too much!! I will stay with the 1 1/2 PVC and replce all the metal I can reach.
Thanks again and have a nice day.
 
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