So the flapper in my toilet tank was hard and broken. I bought a replacement and began by turning the water off to the back of the toilet so I could see what I was doing. After putting the flapper in place I turned the water back on and it won't come out of the ballcock assembly and refill the tank. I pulled the water supply hose out of the bottom of the toilet to make sure the water still worked and it does, however it has a very low water pressure. Should I try and replace my ballcock assembly or is it possible that the low water pressure is the problem? It all worked fine until I turned off the water.