New to me boat and the shower drain does flow well and back up into the sink area unless you shut off the shower and wait for it to drain. Tried flushing the drain out and improved a little. Any idea on how to remove the drain cover so I can get into the drain piping. Its a chrome top drain about 2.5" in diameter. Attempted to pop it off but don't want to damage anything. Not sure if it pops off or screws off. Thanks for any guidance.