1.5" or 2" PVC preferred?

[nervous]

I am installing a kitchensink/dishwasher drain run and have to make a choice. The run is about 12" in length with one 90* turn and a good down running pitch in the cellar. The question is which would be better hydraulically, a 1.5" or 2" drain run? I ask because as I was doing my toilet drain a couple years ago I was told that a 3" pipe would work better hydraulically than a 4" and since that was a short run it made sense. Any thoughts on 1.5" vs 2" in this application?

Thanks

[freddy]

Run your drain in 2" as that would be called for in most codes, also in future to clean out drain line, cable will go down 2" drain with out to much problems. :)

[westcoastplumber]

I am installing a kitchensink/dishwasher drain run and have to make a choice. The run is about 12" in length with one 90* turn and a good down running pitch in the cellar. The question is which would be better hydraulically, a 1.5" or 2" drain run? I ask because as I was doing my toilet drain a couple years ago I was told that a 3" pipe would work better hydraulically than a 4" and since that was a short run it made sense. Any thoughts on 1.5" vs 2" in this application?

Thanks

UPC calls for 11/2 trap and trap arm, 2" verticle and horizontal drain line. I am sure the IPC calls for the same thing. Grade or "Pitch" your horizontal line at 1/4" per foot, remmember, more grade or pitch isn't always better because if the water flows to fast, it will leave the solids behind. Remember, you want to keep the self scouring principles;)

[nervous]

Thanks fo rthe info. I neglected to mention that the kitchen sink is in an islane and I have been mulling a setup similar to this with a couple minor mods to suit the application:

http://www.taunton.com/finehomebuilding/how-to/articles/better-undersink-plumbing.aspx?nterms=61880&ac=ts&ra=fp

Is there any harm in doing the tailpiece and trap in 2" vs. 1.5?

[BHD]

Venting is a need as well. and you said Island sink.

some basic information below,

http://www.rd.com/familyhandyman/content/19540/

http://www.taunton.com/finehomebuilding/pages/fh_174_056.asp

http://www.masterplumber.com/Laws/UPCExcerpts.html

Before using an air admittance valve (AAV) contact your local plumbing inspector to determine if an AAV is allowed

[freddy]

You might look into running 3" pipie with san tee 1-1/2" going to sink. Run 3" pipe 12' or so, tie into 3" sewer then your pipe will work as vent . out of top of the tee fitting you put on a screw plug for cleaning of drain if needed. :)

[drtyhands]

Venting is a need as well. and you said Island sink.

some basic information below,

http://www.rd.com/familyhandyman/content/19540/

http://www.taunton.com/finehomebuilding/pages/fh_174_056.asp

http://www.masterplumber.com/Laws/UPCExcerpts.html

Before using an air admittance valve (AAV) contact your local plumbing inspector to determine if an AAV is allowed
I would not go with the AAV under the flood rim of the sink as the dried soapsud crud will cuase the valve to malfunction.