I'm installing a new shower base and drain. When I fit the base down with the drain attached, the waste pipe is not flush with the drain. It fits within the drain hub but it about about 1/2" below the hub lip. Is that okay? I will solvent weld the pipe and hub but it is on a slab so I can't check for leaks once installed, so just want to be sure that the pipe doesn't have to be flush against the hub.