In article .com,
alath wrote:

First you look at the trap. It is an S-shaped pipe
underneath every sink or drain in my house and probably yours. Could
be in the basement or crawl space maybe in a wall.

I was wondering about the trap. This home is built on a concrete slab
floor. I don't think I am going to be able to get at the trap to take
it apart.

If it's hair in the trap, a gallon of standard laundry bleach poured
down the drain before you go to bed for the night will dissolve it.
Don't use any water in that bathroom for at least eight hours, including
the toilet and sink. If that doesn't clear it out then if it were me I'd
call a plumber. I've found cheap snakes to be useless, and good ones are
expensive and take finesse to use properly. Sure the theory of operation
is uncomplicated, but it takes experience to do a decent job.

This is all based on my own experience of 25 years with a pesky bathtub
drain, I must've tried snaking it myself at least fifty times, which
sometimes improved it for a few months but the slow draining kept coming
back. Over the years I had four or five different plumbers over to snake
it, and that usually lasted about six months. Finally I found a guy who
knew what he was doing and haven't had a single problem since he was
here five years ago.

Incidentally, my house is also on a slab and I even cut a hole in the
kitchen cupboard down by the floor to try to gain trap access and
although I could see the trap there wasn't any room to get in there and
take it apart.