I now have both stems out and I did buy new seat for the faucet and seat wrench but they did not come out easily so I decide I would just put the new stems in and hope the seats were ok. But I think I might have another problem. My cold water line is shut off just before the cold bathtub faucet but due to the plumbing arrangement of the pipes I could not easily just put a valve in close of the bathtub hot water so I put one in that shut all the hot water off. Figured I could live without hot water for a couple of days, if necessary. However when I turn the cold water on in the bathroom sink, cold water comes out the hot water pipe siting out the wall for the bathtub faucet. The flow increase as I turn the tape on more. As long as the cold water tap in the sink is turned of their is not water coming out the hot water pipe in bathroom. I do not understand how/why this could happen.I thought hot and cold water supply line would be completely separate. Any insight would be very helpful. I do not what to put the new stems in if their is an other problem