I am removing the linoleum in my downstairs laundry/bathroom. The reason being is there is a lot of water marks under the floor and we aren't sure if any of the spots is still leaking, plus the person whom put the lino down installed it directly over the drain. The lino backing is sticking to the concrete. Do I remove the backing so there is concrete or can I leave it? There are spots where the backing came off and other spots not. I do know that the installers put a skim coat down but will that even it out.