I’ve found 2 black worms about 3cms in length in my en-suite shower. When I moved them they bled. 
Tonight I found one half way up the wall in the main bathroom. Yuuuuuuuuck!
Does anyone know what they are, I googled it but the images I get are much smaller than the ones I have seen.
I do put disinfectant down the drains in both bathrooms.