hello. my problem is our kitchen sink. whenever we turn on the water, nothing comes out until the count of five. it then stops running till we count to five again, then makes a loud thumping sound before the water runs again. if we turn on the faucet and nothing comes out, we turn it off and it takes about two seconds for another thump like it's catching up to the turn off. we thought it might have been air in the pipes but we have no problem with our bathroom or laundry in the basement. any suggestions?

thank you.