My 2 year old keeps spitting.?

He doesn't do it all the time. He will usually do it when he is drinking something and then walk over to our living room table and spit it out. If we don't stop him he will keep doing it over and over till the cup is empty. He will also just gather spit in his mouth and than spit on the table or floor. I have tried time outs and taking things away and it doesn't detour him from doing it. Should I be concerned?