Replace a P-Trap
That u-shaped piece of pipe under your sink is called a p-trap. They can get clogged which requires replacing or cleaning out the p-trap. Since you are already pulling it out, why not install a no-clog p-trap so you won't ever have to worry about the replacing or fixing your p-trap again.
What is a P-Trap
It's design has two purposes: First, to allow the water from the sink to flow out and keep noxious gas from coming in, and second, to catch items that might go down the drain (wedding rings) before they are swept away. Over time this p-trap can become plugged with hair, dirt, and other debris and the sink will start to drain very slowly.
