Clue to the CoS?

[smellee17]

No: HPFGUIDX 43637

I have been following the discussions about how Voldemort found out 
he was the Heir of Slytherin. I read a post mentioning Voldemort 
probably found the bathroom tap with the snake etched into the metal, 
and I had a thought. If Voldemort found the tap, that meant Salazar 
Slytherin must have made the mark when the school was founded about 
thousand years ago. I hadn't noticed that detail before, but now it 
is bothering me.  They couldn't have had running water, pipes, and 
toilets back then, could they? I think Voldemort had made the snake 
as a clue to those who would come after him. Voldemort says he knew 
he couldn't reopen the chamber without suspicion, so I assumed he  
was leaving clues. Any thoughts? 
signed smellee