When it comes to copper kitchen sink tap, it's very similar to that of a home. To prevent blockages in the drain pipes, you should first check the P-Trap and the roof vents. If these are not blocked, try to remove them by running water down the roof vent pipes. Alternatively, you can also use a drain cleaner or a small bathroom plunger to clear the blockage. If all else fails, you can try a rag in a separate sink. The bottom part of the plunger should be flat, and you should also check the pvc fitting under the sink.