In COS, how could the entrance to the chamber be a relatively modern bathroom?

Salazar Slytherin was a very very powerful wizard and might I add, a smart guy.

When he created the chamber he intended it to last for generation upon generation so that one araw his heir would be able to open it.

I expect he took into account that things change in such a long time. He would have known that the bathroom would be modified a number of times before his heir would attend Hogwarts.

Slytherin was one of the greatest wizards of his time so I suspect he would have found a way to make the entrance to the chamber morph into different forms as time passed.

Personally i think Rowling simply didn't think about it. But since it's now in the book we have to assume that wizards were ahead with plumming, it's not a very complex technology after all. In fact, indoor plumming occurred as early as in ancient Rome. So if the wizards evolved the technology while we muggles devolved during the dark ages, they could well have had working sinks in the 11th century.

for one they're wizards...totally came up with everything earlier...and the kastilyo just roles with the times...maybe the snake was simply carved into something else in the bathroom...but because it was such a strong peice of magic it morphed itself along with the bathroom when it was changed

The chamber was probably magically hidden and the spell wore off after they added the plumbing; or wizards were ahead with bathrooms.

Or J.K. messed up. She may be an awesome Muggle, but she makes mistakes.

Wizards were far ahead of muggles when it came to technology. I believe the chamber was magically hidden, and learned to shape itself. That giant hole, when the sinks open, is probably part of the chamber so when they put the sinks in, the floor was sealed until someone spoke parseltongue, what I'm saying is, the chamber magically formed itself to mold to its own time.

Its hogwarts what do you expect. everything looks like it did when it was first made,

Tom Riddle was down there the whole time twisting and changing the chamber with his dark magic. Or, the bathroom never changed in those fifty years. moaning myrtle was in there for fifty years.

Muggle technology is far behind wizard technology. Faucets and bathrooms have been around for ages, at least in the wizarding world.

Salazer Sythrin created the chamber of 1,000 years nakaraan then Tom Riddle opened it 50 years nakaraan now Salazer Sythrin spoke parseltonge and o did tom tahs how he opended it he so to the sink in the girls bathroom and opened but he blamed Hagrid so how you open is sa pamamagitan ng speaking parsletounge to the snke statues in the girls bathroom
Hope this helps

I don't really know... good tanong though!

If they had time deals back then he could have went to the future but that would b a waste of time.

they're magical, duh :)

They probably just thought it was cool to be different (cringe quote there) and made it like that, but since then, they didn't change the appearance of Hogwarts. (i just realized, Hogwarts is in the dictionary of my computer!!! :0)