How does one keep a sink kosher when using two separate sets of plates and dishes?
The Sink: Separate sinks for washing dishes and preparing foods are recommended. If the two sinks are adjoining, there should be an effective separation between them so that no water or food splashes from one sink to the other.
If there is only one sink, it may be used after it has been completely cleaned, but the inside of the sink should be regarded as non-kosher. No food or dishes should be put directly into non-kosher sinks. There should be separate dish pans and slightly elevated racks under the dish pans for both meat and dairy. Similarly, two sinks which were used before the kitchen was kosher should also be regarded as non-kosher, unless they are stainless steel and were koshered. If the two sinks were koshered, one should be designated for meat and one for dairy.