If you notice water pooling in your copper sink, there may be a few explanations as to why: Copper is a soft metal and is easily bent. Because of this, copper sinks may become slightly inverted at the bottom, either where the drain is installed or around the outer edges.
The first step to correcting this problem is to determine where the bend is. If the bent area is near the drain, you may need to adjust its height to restore the proper slope.
If that is the case, you will want to begin by disconnecting the P-trap from the drain. Have a bucket underneath the connection to catch any water. Then, place a rag in the P-trap to avoid any unwanted odors.
Once the drain has been freed from the P-trap, start by placing a washcloth over the bottom of the sink. Begin lightly pounding with a rubber hammer, ensuring that the bottom of the sink is level, with a slight pitch toward the drain hole. Once level, gently pull the drain to reset the shape of the sink.
After reshaping the sink, remove the rag from the P-trap and reconnect the drain. Be sure to properly reconnect all plumbing and check for leaks at the drain and trap connections.