Clogged Bathtub Drain

Just a basic question of how to unclog. The water does go down the drain, albeit very very slowly. I'm sure this is due to an accumulation of hair/gunk.
I can't figure out how to remove the drain cap. It is the type with a knob that you rotate about 1/4 turn to collapse it to be able to take a bath, and a 1/4 turn the other way to keep it raised for showering. It will not unscrew.
I thought I would first try to unscrew the cap to see if I could access the clog, but I can't even unscrew the cap.
I don't want to have to call a plumber - I'm sure with the right advice this has to be a simple thing.
Should I apply a commercial drain clog product? Is there a simple way to remove the drain cap that I don't know?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dimitrios Paskoudniakis wrote:

Leave the drain cap alone. Remove the overflow/trip lever faceplate. You can run a small snake down that.
Or...connect the Shop Vac and suction at the drain. Cover the o'flow opening with wet rags.
There is nothing "usual" or "standard" about tub drain clogs. There are a dozen different drain layouts and fittings and while some clogs are near the tub, others can be as far removed as the lav basin tie-in.
You play it by ear and try things till it flows freely.,
I discourage chemicals because they don't touch the hair clogs but DO attack many of the piping materials.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 29 Jul 2007 12:06:02 -0400, Dimitrios Paskoudniakis wrote:

You could pour a commercial drain acid (Sulfuric) through the drain opening but it would discolor any chrome. I can't tell you how to remove that cap.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
on one i use a foot of #12 elec wire ,put a hook on the end and just hook the clog and pull it out. on another ,i bring the garden hose in the window, put wet rags around it in the drain and the overflow and flush it out... so ,i got one tub that clogs in the trap and one that clogs abbout 8 foot downstream.lucas
http://www.minibite.com/america/malone.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
For hair and grease, use a drain cleaner that has the word "hydroxide", like potassium hydroxide.
For calcium scale, use a drain cleaner that says acid like "hydrochloric acid".
Bath tub drains are often grease, hair, and body oils. For that, I'd first try a hydroxide drain cleaner. Follow directions on the package.
--

Christopher A. Young
You can\'t shout down a troll.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.